Symposium SM4 : Engineering Biointerfaces with Nanomaterials

The cell membrane is the host of a multitude of highly dynamic biological processes crucial to the inner life of the cell. In particular, membrane proteins play a crucial role in sensing, signal transduction and transport. However, due to the difficulties associated with purifying, handling and conjugating membrane proteins, their integration into biosensors or biophysical assays have lagged considerably in comparison to soluble proteins. I will present newly developed functionalization procedures to interface membrane proteins with surfaces, while preserving their native membrane environment.

Nanodiscs are soluble scaffolds for membrane proteins [1, 2]. They consist of nanometer-sized discoidal phospholipid bilayers that are surrounded by an amphipatic polymer, such as the membrane scaffold protein [1] or styrene-maleic acid (SMA) co-polymer [2]. Membrane proteins embedded in lipid nanodiscs maintain their membrane-integrated state in this soluble complex, and can therefore be handled similarly to soluble proteins. SMA co-polymers are highlighted as agents for detergent-free purification of membrane proteins, which can solubilize membrane proteins in presence of their native lipid membrane environment. This approach considerably eases purification of membrane proteins, but does not enable their detection or immobilization as such. To facilitate conjugation of SMA-nanodiscs to surfaces, nanoparticles and fluorophores, we add a thiol group to SMA. To accomplish this, we exploit the reactivity of maleic anhydride moieties in SMA towards amines to modify the polymer with cysteamine. Thus, we equip the polymer with a sulfhydril group (SMA-SH). This sulfhydryl group is then modified with thiol-reactive probes, such as maleimide derivatives of fluorophores and biotin. The SMA-SH nanodiscs are characterized with gel filtration, dynamic light scattering and electron microscopy.

We find that SMA-SH enables the functionalization of membrane proteins with a variety of different probes, while not requiring any mutation or chemical modification of the protein itself. We anticipate that this versatile approach will find application in membrane protein purification, in biosensing, as well as in a wide range of biophysical assays, such as single-molecule TIRF measurements, AFM, optical or magnetic tweezers.

1. Bayburt, T.H., Y.V. Grinkova, and S.G. Sligar, Self-assembly of discoidal phospholipid bilayer nanoparticles with membrane scaffold proteins. Nano Lett., 2002. 2: p. 853-856.
2. Scheidelaar, S., et al., Molecular model for the solubilization of membranes into nanodisks by styrene maleic acid copolymers. Biophys. J., 2015. 108: p. 279-290.

Biological applications can benefit immensely from nanoscale patterning of biointerfaces that control biomedical functions. Patterning of biointerfaces can greatly increase the available surface area so that they can be coated with larger doses of therapeutic agents. We demonstrate nanopatterning of poly (L-lactic acid) (PLLA) – a prototypical material commonly used as a template for cell growth and in coronary stents.
A master pattern consisting of a periodic array of nanohole and nanocone arrays was transferred to a PDMS mold. Periodically patterned PLLA surfaces with nanohole and nanocone arrays of period ~700 nm were synthesized from a PDMS mold using soft lithography and double replication. We started with a master pattern consisting of a periodic array with sub-micron pitch patterned on polycarbonate substrate. A mixture of PDMS prepolymer and curing agent was poured directly onto the master substrate. After curing, PDMS was peeled off from the master substrate to expose the inverse pattern on the PDMS surface. We used the patterned PDMS mold to transfer the pattern onto PLLA films by (i) drop-casting the PLLA solution in chloroform on patterned PDMS, and (ii) spin-coating PLLA films on glass substrates and imprinting with the PDMS mold under elevated pressure and temperature. SEM images of the patterned PLLA films showed excellent long range periodicity, but superior transfer of patterns for drop-casting, whereas nanoimprinting the PLLA films resulted in shallower and less resolved features. Measurement of contact angles showed that nanopatterning induced hydrophobic behavior in PLLA films, with an increase of contact angle from 72° for the unpatterned film to 108° for the patterned film.
The patterned nanohole and nanocone PLLA surfaces were conformally coated with a prototypical drug sirolimus by brush and spray coatings, and characterized with SEM to confirm adhesion and morphology of the coatings. We measured the release rate of drugs from patterned and unpatterned (control) PLLA surfaces initially coated with the same amount of drug to study the beneficial biomedical aspects of patterning. We will describe preliminary results that indicate that patterned biopolymer surfaces may hold therapeutic coatings for a longer time. These findings can significantly improve the application of functional patterned biomaterials for drug release and in enhancing cell growth.

This contribution will present surface-initiated (controlled) polymerization techniques as a powerful toolbox to generate biologically active and responsive polymer interfaces. Polymer coatings prepared via surface-initiated polymerization are dense arrays of polymer chains that are all linked covalently with one of their chain ends to the underlying substrate. If the reactive sites are placed sufficiently close together, this forces the polymer chains to stretch out and results in a molecular brush-type coating. This presentation will discuss the preparation and properties of interactive and responsive polymer brushes prepared via post-polymerization modification of reactive precursor films that are obtained via surface-initiated controlled radical polymerization. After discussing different post-modification strategies and the characterization of the location and distribution of functional groups in such ultrathin coatings, their use for the fabrication of model substrates to study cell adhesion and proliferation or as functional films for cell sheet engineering will be discussed.

Collagen, the most abundant protein in mammals, plays a crucial role in tissue development and regeneration. Since elevated activity of collagen remodeling is associated with numerous pathologic conditions (e.g. tumor, fibrosis, arthritis), ability to target unstructured collagens in diseased tissue could lead to new diagnostics and therapeutics, as well as applications in regenerative medicine. Previously, we reported the new strategy for targeting denatured collagens that is based on triple helical hybridization between collagen strands (of diseased tissues) and synthetic collagen mimetic peptide (CMP) also referred to as collagen hybridizing peptide (CHP). This hybridization results in robust collagen specific binding in vivo which allows detection of degraded collagens in diseased tissues with persistent wound healing activity (e.g. tumor, arthritis). In this presentation we will describe our on going investigations into elucidating the mechanism of the hybridization as well as experiments verifying the CHP’s collagen binding capacity both in vitro and in vivo. We will also discuss two new CHP-mediated self-assembling systems which are based on nanoparticles and beta-sheet forming peptides (B-CMPs). CHP conjugated nanoparticles allow controlled NP assembly as well as specific detection and removal of denatured collagens from protein mixtures. B-CHPs based on FKFE and GPO repeats assemble into highly water-soluble nanofibers and nanosheets which exhibit improved affinity to denatured collagen because of multi-ligand effects. Due to its neutral and hydrophilic nature, CHPs are inert peptides exhibiting high serum stability. It is also a structurally simple peptide that can be readily conjugated to various imaging and therapeutic modalities. The CHP offers an entirely new way to target the microenvironment of diseased tissues which may lead to new opportunity for management of pathologic conditions associated with high level of collagen degradation and remodeling.

Collagen is the major structural proteins in mammals, providing mechanical stability, elasticity and cell-conducive environments to connective tissues such as tendon, skin, bone and cartilage. The molecular and higher level of ordered structures of collagen has gone through the nature’s evolutionary process, supporting diverse biological functions. In an effort to elucidate the assembly mechanism and to develop advanced functional biomaterials, various synthetic collagen-like peptides have been demonstrated as potential collagen-mimetic systems, which strongly contributed to understanding triple helix formation. However, controlling the assembly of building blocks into the higher level of the ordered structures that incorporate the desired biochemical functionalities is still challenging and needs to be addressed. Here we show a novel approach to developing collagen mimetic materials based on rational design of functional biomacromolecules using evolutionary screening of M13 bacteriophage (phage). Single crystal hydroxyapatite-binding phage was identified using major coat protein-engineered library and was found to display collagen-like peptide sequence on the nanofibrillar structure. We found that the identified collagen-like phage can be assembled into long range ordered supramolecular film composed of periodically banded (~240 nm) microfibrillar structures by using controlled pulling method. The assembled structural films were demonstrated as potential collagen-mimetic materials showing the capability to direct bone cell and hydroxyapatite crystal growth. Reproduction of the characteristic banded fibrous structures using large building blocks may pave the way to better understanding the structure-function relationship. Our results demonstrate how the evolutionary engineering approach can be exploited to undermine new macromolecular structural building block with desired biological functions for the rational design of biomimetic system. We anticipate that our approach to be one of the starting point for developing novel biomaterials exhibiting biomolecule-mimetic or enhanced biological activities.

Cephalopods possess remarkable camouflage capabilities, which are enabled by their complex skin structure and highly advanced central nervous system. These animals’ unique characteristics have served as a source of inspiration for the development of novel functional materials and devices. Within this context, recent studies have focused on investigating the self-assembly, optical, and electrical properties of reflectin, a protein that plays a key role in cephalopod structural coloration. For example, the reflectin A1 isoform has been shown to function as an effective proton conduction medium, enabling its use in protonic transistors. Herein, we report the discovery that the reflectin A1 isoform from Doryteuthis pealeii also constitutes an effective material for the growth of mammalian cells, including relatively difficult-to-culture human neural stem/progenitor cells. Our findings may hold relevance both for furthering understanding of neural stem/progenitor cell binding mechanisms and for developing a platform with untapped potential as an exquisitely sensitive active material for bioelectronic devices.

Injuries associated with tendons are among the most common trauma, with over 250,000 rotator cuff tendon repairs performed annually in the US[1]. The native tendon-bone (TB) interface is comprised of diverse tissues, namely, tendon, fibrocartilage and bone[2]. Current clinical approach, mechanical fixation, for tendon reconstruction grafts often fail to reestablish this hierarchical transition post-surgery[3]. Therefore, there is a need for new augmentation matrices to improve the biological fixation to obtain a scarless healing at TB interface.

Our approach to TB integration focuses on the use of biomimetic, nanofibrous scaffolds incorporated with bioactive agents. Growth factors injected into the zone of injury facilitates restoration of the normal function of TB interface[4]. Transforming growth factor β3 (TGF-β3) is upregulated during the development of TB insertion[5]. Connective tissue growth factor (CTGF) is sufficient to differentiate stem cells into tendon specific cells[6]. The objectives of this study are to 1) fabricate polycaprolactone-based (PCL) scaffolds containing TGF-β3, CTGF and nano-hydroxyapatite (nHA), where concentrations of CTGF and nHA change in opposite directions, while TGF-β3 is located in the middle portion of the nanofibrous composites [such organization is expected to contribute to generation of tendon (in CTGF rich zone), fibrocartilage (by TGF-β3) and bone (in nHA rich zone)], 2) establish controlled release of TGF-β3 and CTGF from nanofiber scaffolds, and 3) investigate stem cell behavior on these scaffolds. Such a design is proposed for the first time and expected to contribute to scar-free TB interface regeneration.

Our findings show that linearly varying nHA distribution can be accomplished across the scaffold thickness that is also the case in native TB interface[7]. Incorporation of nHA into PCL nanofibers led to increased mean fiber diameter from 361±9nm to 459±21nm, and a decrease in contact angle from 120.01±2.77 ° to 115.24±1.17 °. We have also demonstrated that TGF-β3 can be incorporated into nanofiber scaffolds with electrospinning and released in a sustained manner. We are to investigate the response of stem cells on the proposed scaffolds for interface-related matrix formation (collagen and glycosaminoglycans) and expression of relevant markers such as collagen types I, II, and X.

This study not only reveals the importance of design and use of biomimetic scaffolds in tissue engineering but also yields new insights into the effect of bioactive molecules on interface regeneration by controlling their local availability. These discoveries will serve as the foundation for the development of biomimetic tissue engineering technologies aimed at promoting biological graft fixation.

[1]Gulotta+ Am J Sports Med 2009; [2]Benjamin+ J Anat 1986, [3]Rodeo+ J Bone Joint Surg Am 1993; [4]Gulotta+ Clin Sports Med 2009; [5]Galatz+ J Orthop Res 2007; [6]Lee+ J Clin Invest 2010; [7]Genin+ Biophys J 2009.

Each year, traumatic brain injuries (TBI) contribute to substantial numbers of deaths and cases of permanent disability in civilian and military populations. Medical therapies remain few and experimental, while clinical management relies on endogenous rehabilitative powers and therapy, which is lengthy, costly, and has wide variations in achieved benefits. Our group has reported [1] that, in addition to the biological cues, nano-scale physical features of the cell receptor-level environment significantly influence and regulate astrocyte behavior. To harness the potential for a biomaterials-based therapy to provide instructive cues to regulate astrocyte behavior, the immediate goal is to identify, quantify, and prioritize those features that supply the most instruction to the cells, alone or in combination, and identify strategic combinations of these features that direct astrocytes away from the reactive phenotype. In the present study, we present the results of a statistical analysis combined with a novel use of cluster analysis. Four biomaterial properties from four cell culture environments were characterized for nanoscopic elasticity, work of adhesion, surface roughness, using novel along-fiber atomic force microscopy and for surface polarity, using contact angle measurements. Possible clustering of four-dimensional attribute data for using k-means analysis (point-to-cluster-centroid minimization) revealed well-separated clusters of biomaterials property combinations. A similar statistical + cluster analysis of astrocyte responses revealed trends and correlations between the biomaterials property combinations and the astrocyte response outcomes. Studies such as ours will produce critical design rules for elucidation of recovery-promoting nanophysical cues that will enable the development and optimization of innovative scaffolds and biomaterial therapies to enhance neuronal survival and regeneration.
[1] Tiryaki, VM, Ayres, VM, Ahmed, I, Shreiber, DI. Differentiation of reactive-like astrocytes cultured on nanofibrillar and comparative culture surfaces. Nanomedicine, 2015 10(4): 529–545 (DOI: 10.2217/NNM.14.33)

Both in vivo and in vitro the function and fate of cells are affected by factors such as mechanics, topography, chemistry and geometry. Thus the ability to efficiently control such parameters is of critical importance in regenerative medicine to e.g. restore damages tissues, but also has great potential in diagnostic and pharmaceutical applications for drug screening. Although the size and importance of this ambition, there is relatively little knowledge on how to specifically engineer such environments from first principle, hence the majority of the breakthroughs have been fuelled by serendipitous discoveries. This has driven a push in the design of the experiments from exploring relatively few parameters to having platforms accommodating high-content screening. To this end, we have developed a number of novel high-content platforms to screen the cell-substrate interactions for a range of different cell types. We have demonstrated that it is necessary to investigate all cell types required for a given application as the response varies significantly from cell type to cell type.
We apply a lithographic approach whereby precise environments (topographical and mechanical) can be precisely engineered. This approach also allows us to parameterise the designs providing a simple yet effect means to systematically explore large sample sets. The lithographic process uses electron beam lithography to reach length scales below 1 μm and combines this with reactive ion etching to prepare master substrates. This is a time consuming process thus we apply a replication step using injection moulding whereby 100s-1000s of polymer replicas can be made in a highly reproducible and automated manner. The lithographic process is a traditional route to fabricate specific patterns, however, the patterns manufactured will all have the same height/depth due to the etch process. It is well know from the literature that the vertical dimensions also play a role in the cellular response. Therefore we have developed a novel single-step process by which the importance/relevance of depth/height can be explored in a high-throughput manner.
Using these developed platforms we have now established a robust microscopy and data analysis platform where the many design parameters easily can be explored using a range of cell types. Examples will be given from various systems.

1. Introduction: Slab optical waveguide (SOWG) spectroscopy by which in situ observation of UV-vis. absorption spectra from adsorbed molecules on solid/liquid interface. We have reported direct electron transfer (DET) reaction of cytochrome c (cytc) adsorbed on ITO electrode could be observed by SOWG spectral change due to electrode potential scan, and that cytc adsorbed on ITO electrodes kept DET activity without addition of any promoters or mediators.[1-4] In this presentation, we will report the effect of ITO electrode surface modification with 10-carboxydecylphosphonic acid (10-CDPA) on DET of cytc and hemoglobin immobilized on surface modified ITO electrode.
2.Experiments : A 50-mm thick glass plate was used as a SOWG, and the thickness of ITO films were about 20 nm. The cell length was about 10 mm and the surface area of ITO-SOWG covered with sample solution was about 1.0 cm². In electrochemical measurements, the ITO electrode potential was controlled with a potentiostat (PAR Model 273A). The reference electrode was Ag/AgCl. Horse heart cytc was purchased from Sigma and used as received. the phosphate buffer was used as a solution (pH 7.2). ITO electrode was immersed in tetrahydrofuran (THF) solution including 1 mM of 10-CDPA (Dojindo Molecular Technologies, INC., Japan) for 10 min, and washed in THF with ultrasonic washing for 3 min.
3. Results and Discussion : The cytc sample solution of 10 mmol/dm³ in phosphate buffer saline (PBS, pH=7.41) solution was put on the electrochemical cell to immobilize cytc on the 10-CDPA modified ITO electrode surface for 10 min. Exchanging the PBS solution in the cell to fresh one 100 times decreased less than 10 % of absorbance at 408 nm. With bare ITO electrode, just 3 time exchanging decreased the absorbance at 408 nm about 10 % or so, thus 10-CDPA much affected the immobilization of cytc. The CV of cyt c immobilized on 10-CDPA modified ITO wasperformed. The peak potentials of reduction and oxidation reaction were about 0.031 and 0.048 V, respectively. The peak separation seemed to be smaller than those with the cyt c immobilized on bare ITO electrode, indicating the increase of the ET rate constant. In situ observation of SOWG spectroscopy showed the repeated peak change on Soret band between 408 and 416 nm with ITO electrode potential scan between -0.3 and 0.3 V. Additionally the excellent effect of 10-CDPA modified ITO on strongly immobilizing cytc was shown from the SOWG results with changing PBS solution.
References [1] N. Matsuda et al., Thin Solid Films, 438-439, 403 (2003). [2] N. Matsuda et al., IEICE Trans. Electron., E-96C, 389 (2013). [3] N. Matsuda et al., IEICE Trans. Electron., [4] N. Matsuda et al., IEICE Trans. Electron., E-96C, 152 (2015).

Living cells exchange the material with their environment through endocytosis. Dynamin is a GTPase protein, which induce vesicle fission by polymerizing into helical structure at the neck of budding vesicles in synapse and receptor (or clathrin)-mediated endocytosis. We have used high-speed atomic force microscopy (HS-AFM) to investigate dynamin polymerization on lipid bilayers adsorbed on silicon nanowire substrates which mimic the curved membrane regions. This study also demonstrates that AFM can be a useful tool to understand dynamics and mechanism of protein assembly.

Recently, 3D nano and micro-fabricated platforms have been used for multiple in vitro biomedical applications. In particular, nanopillar arrays have gained large importance as a valid tool to manipulate cells and record electrical activity (i.e. action potentials) from electrogenic cells.^1,2. Effectively, the geometry as well as the material nature of those 3D nanostructures induce cells to have a specific response and often to re-adapt their shapes to the nanostructures³. This re-arrangement occurs at the cellular membrane as well as at the intracellular environment. In order to investigate these phenomena, a high resolution microscopical method is needed to visualize the actual proximity of the cell and the nanopillar at the cell-pillar interface. Since fluorescence microscopy has limited resolution for this application⁴, a technique that allows high-resolution visualization of organelles as well as whole cells on array at the nanoscale needs to be explored.
Here, we develop a 3D method to correlate fluorescently labelled (i.e. dyes, protein tags) intracellular organelles with ultrastructure of cross sections, created by focused ion beam scanning electron microscopical (FIB-SEM) milling and imaging, of the same samples. First, we investigated intracellular structures with fluorescence microscopy. Then, we developed an ultra-thin resin embedding method of cells with contrast-enhancing agents to improve the visualization of intracellular compartments in SEM. Having an extremely thin resin layer on top of cells allows us to further visualize, with conventional SEM, entire cells spreading and growing on nanopillar arrays while resolving very small intracellular and extracellular structures which can be damaged by standard SEM preparation techniques (i.e. critical point drying). In fact, our unique technique allows in situ SEM imaging of whole cells, followed by (spatially controlled) sequential transverse sectioning with FIB in order to visualize intracellular organelles in 3D in response to nanopillars and, if needed, to prepare a thin TEM lamella for further investigations - all of the same specimen and region of interest. Finally, we successfully correlated in 2D and 3D fluorescence images with high resolution, high contrast SEM-FIB images to resolve entire intracellular structures eventually deforming (i.e. nuclei) and accumulating (i.e. endocytic vesicles) in the proximity of the nanopillars.
References
1. Xie, C., Lin, Z., Hanson, L., Cui, Y. & Cui, B. Intracellular recording of action potentials by nanopillar electroporation. Nat. Nanotechnol. 7, (2012).
2. Angle, M. R., Cui, B. & Melosh, N. A. Nanotechnology and neurophysiology. Curr. Opin. Neurobiol. 32, (2015).
3. Santoro, F. et al. Interfacing Electrogenic Cells with 3D Nanoelectrodes: Position, Shape, and Size Matter. ACS Nano 8, (2014).
4. Hanson, L. et al. Vertical nanopillars for in situ probing of nuclear mechanics in adherent cells. Nat. Nanotechnol. 10, (2015)

Here, we describe our efforts in utilizing the cellular membranes of living bacteria to template the interfacial growth of rare earth (Re) phosphates, with the goal of creating new biologically organized functional architectures of Re materials and to understand how this modification influences the behavior and environmental interactions of bacterial organisms. Our approach uses the high affinity of Re ions with phosphate (both free and membrane bound), forming insoluble RePO₄ urchin- and plate-like nanostructures at the surface of bacteria through binding with membrane lipopolysaccharides (LPS) as well as intracellular phosphate released upon membrane permeabilization due to damage from Re-mediated dephosphorylation. Using a library of Re oxide (ReO) nanoparticles (NPs) as a source of Re ions, we have demonstrated the growth of RePO₄ on both Gram-negative (E. coli and Salmonella) as well as Gram-positive bacteria (Staphylococcus), and examined the effect of Re exposure on bacterial viability using assays of cellular stress and growth dynamics, characterizing the resulting RePO₄ nanostructures through TEM (both standard and in-situ imaging in H₂O), SEM, and live cell confocal laser scanning microscopy. In E. coli, our results show differential effects of ReO NPs (depending on the specific Re) on bacterial viability in low phosphate growth medium that is corroborated by high reactive oxygen species (ROS) release. As the concentration of phosphate in the medium is increased, however, the effect of Re on viability is diminished, even with the continued binding of Re to the bacterial membrane and formation of RePO₄. Significantly, the presence of these phosphate nanostructures alters collective bacterial behavior (swarming motility and biofilm morphology) and reduces murine macrophage recognition, effects we attribute to obscuration and/or modification of LPS and other phosphate-containing membrane components. We have also examined the interaction of binary mixtures of ReOs with both Gram-negative and Gram-positive bacteria to form mixed RePO₄ structures, demonstrating the patterning of Re binding on dividing bacteria using SEM and elemental mapping, and have characterized the optical spectra of mixed Re bio-hybrids containing at least one optically-active Re component. Overall, in addition to providing a new route to bio-templated materials, our research shows that the interaction of Re materials with bacteria may have complex environmental and biological consequences that overshadow any simple effects of cellular viability.

The virus like particles (VLP) derived from the bacteriophage P22 provides an opportunity for constructing catalytically functional nanomaterials by directed encapsulation of enzymes into the interior volume of the icosahedral capsid. Directed enzyme encapsulation has been genetically programmed allowing biosynthesis and directed self-assembly of desired enzymes within the roughly 60 nm diameter P22 capsid. The resulting nano-reactors cencapsulate multiple copies of the cargo enzymes, densely packaged within the capsid at local concentrations that mimic predicted high intracellular macromolecule concentrations. Using enzymes derived from many different organisms, we have encapsulated multi-enzyme pathways within the P22 capsid through a process of directed self-assembly. The resulting nanoreactors demonstrate the bioengineering of robust and complex coupled catalytic nanomaterials.
Using these nanoreactors, having single or multi-enzymes encapsulated within them, as individual building blocks we can extend the utility of the system towards complex materials fabrication. Through the directed hierarchical assembly of P22 nanoreactors we can create materials with long-range order that exhibit complex coupled catalytic behavior through communication of individual P22 nanoreactors.

Ni-P composite coatings containing SiC and SiO2 nano-particles deposited on 316L Stainless Steel. The friction and wear behavior of as plated composite coatings were investigated utilizing a pin disk wear tester under non-lubricated condition.316L Stainless Steel rings are the main components of gas turbine compressor at final stage due to low thermal expansion, which are consecutively in taction contact with compressor blades. Ni-P composite deposition creates an expendable coating to provide the sealing effect between the ring and blades of gas turbine compressor. Friction and wear test were conducted in sliding speed of 1.0 m/s and applied load of 1, 5, and 10 N. The experiment indicates that the friction coefficient of the composite coatings is decreased with incorporation nano-particles through Ni-P electroless coating. Further, SiO2 nano-particles provides lower wear resistant due to the lower hardness value compare to SiC nano-particles that depict higher wear resistant. Finally, applying heat treatment improves the hardness and wear resistant of both nano-particles composite coating relatively.

Self-assembled Peptides on two-dimensional (2D) materials like Graphite and minerals such as mica have already been studied due to their usages in the fields of surface chemistry, biosensor, bioelectronics and so on. A number of parameters (such as temperature, concentration, peptide sequence, pH and incubation time) which could affect the self assembly behavior of peptides have been investigated. Meanwhile, the conformation about peptides at interface was characterized by scanning probe microscopy such as Scanning Tunnel Microscopy (STM) and atomic force microscopy (AFM). All these studies shows that self-assembled peptides extending along one dimension gave a six-fold symmetry, which is related to the underline substrate. However, so far some fundamental questions about the crystallographic orientation as well as lattice matching mechanism of peptides on 2D materials have been rarely explored.
Chemical vapor deposition (CVD) method can provide single crystals of triangular shape MoS₂. The atom arrangement of MoS₂ around edge always has a certain facet and it can be used as a landmark to identity the crystallographic orientation of self-assembled peptides. After incubating peptides on the surface, peptides revealed ordered structures with six-fold symmetry with a unique angle from the edge of CVD MoS₂. From the high resolution AFM images, we can get the orientation and periodicity information of self-assembled peptides. By using the same way, we can also determine the orientation of peptides on other 2D materials. Based on the results, we propose a model to explain the periodicity matching mechanism between peptide ordered structures and the atomic lattice of 2D materials. The molecular recognition of self-assembled of peptides on the single-layer MoS₂ would open a new door for further engineering of the electrical properties of 2D nanomaterials.

Reference
Selective Detection of Target Proteins by Peptide-Enabled Graphene Biosensors Khatayevich D, Page T, Gresswell C, Hayamizu Y, Grady W, Sarikaya M. Small, 10(8),1505(2014)
Controlling self assembly of engineered peptides on graphite by rational mutation. Christopher R.So, Yuhei Hayamizu, Mehmet Sarikaya. ACS Nano, 6, 1648(2012)
Controlling the surface chemisty of graphite by engineered self-assembled peptides. Dmitriy Khatayevich, Yuhei Hayamizu, Mehmet sarikaya, Langmuir, 28, 8589(2012)

Peptides have demonstrated self-assembly on two-dimensional materials, such as graphite, exhibiting long-range ordered nanostructures with six-fold symmetry. So far, we found that the self-assembly process of graphite binding peptide (GrBP5) can be divided into 3 steps: (1) binding, (2) diffusion, and (3) ordering.¹ However, due to the technical difficulty in the atomic force microscopy, the mechanism of the diffusion process is not fully understood. As a most related work, the surface diffusion of polymers has been investigated previously, and hopping effect was proposed as a new phenomenon against the traditional view of the Brownian motion.²
In this work, we observed two phenomena; (1) random walk and (2) anisotropic diffusion in the diffusion process of peptides self-assembling on boron nitride (BN) surface. Fluorescent tagged peptides have been utilized to monitor the diffusion of individual peptides in real-time, and the obtained images were analyzed by single-molecule tracking method.
The fluorescent-tagged peptide was found to keep the ability of self-assembly, while fluorescent molecules by itself do not show the ordering but a cluster formation. From the results of fluorescent microscope images, we found that the peptide diffuses on the surface with a random walk for a short time interval. In contrast, for the long time interval, it shows an anisotropic diffusion with six-fold symmetry. Our observations do not follow the conventional Brownian motion. More interestingly, we found that peptides show unique intermolecular interactions, keeping a certain distance with each other. In the presentation, we will discuss quantitative physical parameters in the diffusion process, derived from statistical analysis.

Reference
(1)So,C.Y.;Hayamizu,Y.;Yazici,H.;Gresswell,C.;Khatayevich,D.;Tamerler,C.;Sarikaya,M.ACS NANO 2012,6(2),1648
(2)Skaug,M.J.;Mabry,J.N.;Schwartz,D.K. J.Am.Chem.Soc.2014,136,1327

Different strategies are being investigated to reach optimum duration and conditions for endothelium healing as a critical aspect of enhancement for drug eluting stents. In this work, a nanoarchitectured system is proposed as surface enhancement for drug eluting stents. Highly oriented nanotubes were vertically grown on the surface of a biocompatible Ti-based alloys, as potential material for self-expandable stents. The fabricated nanoarchitectured system is self-grown from the same material as the potential stent substrate. This material is also proposed to enhance endothelial proliferation while acting as drug reservoir to hinder Vascular Smooth Muscle Cells (VSMC) proliferation. Two morphologies were prepared to investigate the effect of structure homogeneity on the intended application. They were characterized for morphological investigation using Field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD), Raman spectroscopy, Energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Nanoindentation technique was used to study the mechanical properties of the fabricated material. Cytotoxicity and proliferation studies were done and compared for the two fabricated nanoarchitectures versus smooth untextured samples using in-vitro cultured endothelial cells. Finally, drug loading capacity was investigated practically and supported by computational study of release profile using COMSOL^® Multiphysics software.

Organic electrochemical transistors devices1, based on the conductive polymer PEDOT:PSS, have been demonstrated in chemical and biological sensing: while accurate in determining the size of individual ions in solution², similar devices break down if challenged with complex mixtures, due to the lack of spatial resolution. Here, we modified a conductive PEDOT:PSS polymer to include extra non-continuous scales in the device. This comprises super-hydrophobic SU8 pillars positioned on the substrate to form a non-periodic square lattice, in which the distance between the pillars smoothly transitions from the center to the periphery of the pattern³. The pattern incorporates a finite number of micro-electrodes in a line that represent the active or sensitive spots of the device. The entire system is coated in cascade with a conductive PEDOT:PSS polymer and by a fluorocarbon polymer which assures the hydrophobicity of the device⁴. A solution on a similar device would maintain a spherical shape as suspended in air. Due to its curvature, Marangoni convective flows develop within the volume of a drop of solution⁵. The competition between convection and diffusion will cause a spatial separation of biological species that would depend on the size and charge of the species in a solution. On realizing a time and space resolved measurement of the solution, the described device may operate the identification and separation of different species mingled up in a solution with high sensitivity, selectivity and reliability.Here we operate the identification of the “waste deposit” of cell culture medium upon interaction with circulating cell isolated form peripheral blood sampling of health, sub-clinical and colon cancer patients. The culture mediums were conditioned during a short-time cultivation of fourteen days performed as previously described⁶. The unsupervised classification of the described datasets into defined groups with a small error suggests that the method may be used for the evaluation of the health status of patients even by not trained or minimally trained personnel, or for exploratory data analysis to find hidden patterns in data reflecting the ongoing patient assessment, which may both have major benefits for the national health care.
1 Owens, R. M. et al. Organic Electronics at the Interface with Biology. MRS Bulletin 35, 449-456 (2010)
2 Coppedè, N. et al. Diffusion Driven Selectivity in Organic Electrochemical Transistors. Scientific Reports 4, 1-7 (2014)
3 Gentile, F. et al. Non periodic patterning of super-hydrophobic surfaces for the manipulation of few molecules. Microelectronic Engineering 111, 272-276, (2013)
4 Gentile, F. et al. Superhydrophobic Surfaces as Smart Platforms for the Analysis of Diluted Biological Solutions. ACS App. Mat. and Int. 4, 3213–3224 (2012)
5 Tam, D et al. Marangoni convection in droplets on superhydrophobic surfaces. Journal of Fluid Mechanics 624, 101- 123 (2009).
6 N. Malara, et al. Small. 2014 Nov 12;10(21):4324-31

Anti-inflammatory agents have been broadly used in neural microelectrodes to reduce reactive tissue responses to the implanted electrodes. However, some of the major technological barriers still remain challenging in delivery of compounds to the brain including (1) the burst effect of the drug, (2) the large amount of neuronal killing zone around the inserted probe, and (3) the uncontrollable amount of drug in specific time periods. To overcome these challenges, we proposed a method for fabrication of Dexamethasone (DEX)-loaded conducting polymers.
The objective of this research is to study the release of an anti-inflammatory agent DEX from biodegradable microparticles made of poly (lactide-co-glycolic acid) (PLGA) that are embedded in conducting polymer poly (pyrrole) (PPY). The fabrication process involved electrojetting and electrochemical polymerization techniques, respectively. First, DEX-loaded PLGA solution (4/2% PLGA, benzyltriethylammonium chloride respect to the Chloroform) were electrosprayed on gold (Au) substrates with applied electrical field of 100kV.m^-1 and fellow rate of 500µL/hr. Then PPY was electrochemically polymerized around microparticles with a current density 0.5 mA.cm^-2 in 5 different deposition time (i.e. 1min to 8min) from a solution of 0.2M PPY and 0.2M sodium-p-styrenesulfonate. Additionally, the surface morphology and size of the microspheres PPy coated microparticles were characterized using Field Emission Scanning Electron Microscopy (diameter 3.45±0.31µm). Finally, we quantified the release profile of DEX from microparticles and PPY coated-microparticles using UV-Vis spectroscopy at wavelength of 242nm. We have successfully demonstrated (1) the fabrication process of DEX-loaded PLGA particles coated by PPY (2) the controlled release of drug (3) the fabrication of uniform microspheres in terms of size and morphology. In the future, we will investigate on-demand release of DEX from actuated PPY microcapsules using electrical stimulation. This method has a potential application for controlled release of nerve growth factors in nerve regeneration.

DNA polymerases are important enzymes that replicate DNA molecules with very low error rates – about one error in 10⁵ bases. Recently, it was found that the replication process can be electrically monitored by attaching a Klenow fragment of polymerase I to the surface of a carbon nanotube and monitoring the current along the tube [1]. In this talk, we report results from computational studies on DNA polymerase nanocircuits. We first perform classical molecular dynamics (MD) calculations to get snapshots of different enzymatic stages, particularly the open state (no DNA binding) and the closed state (DNA double helix binding). We then use density functional theory (DFT) and Keldysh non-equilibrium Green’s function (NEGF) formalism to calculate transmission coefficients and currents for each enzymatic state. Our results show that the transmission spectrum and the currents change by 30% when the enzyme moves from the open to the closed state, which is similar to what has been observed experimentally. However, the current at zero bias is similar when different nucleotides are attached, which prevents sequencing. We also investigate modified nucleotide analogs, in which some of the oxygen atoms are substituted by sulfur or chlorine [2]. Without bias the calculated signals are still similar, but we find that applying a positive gate potential can distinguish A/T from C/G, and also identify T. However, distinguishing between the remaining possibilities needs additional modifications.
[1] T. J. Olsen et. al., JACS 135, 7855 (2013).
[2] K. M. Pugliese et al., JACS 127, 9587 (2015).

Scientists have been pursuing to unravel informations about cellular-level behaviour, from pathological study of cell growth and division to genetic study of psychiatric or cancer disease. However, material choice and design is comparatively crucial for obtaining precise cellular-level biosignals. Various kinds of microlelctrode arrays have thus been developed targeting to measure these small-scale signals in recent years. In particular, 3D structural electrodes have out stand other planer electrodes in aspects of non-invasiveness and better electrical coupling for various biosignal recording.

In this study, we present the detection of rhythmic electrical signal detection, specifically ventral and atrium signals, of biological organism using functionalized biocompatible carbon nanotubes (CNTs) to demonstrate the applicability of 3D CNTs electrodes as a tool for pathological study of living organisms. The CNTs were developed on three-dimensional gold electrodes at low temperature (≦400^oC) for long-term and biosignal sensing. With high surface area, capacitance and biocompatibility, 3D funtionalized CNTs improve coupling coefficient and signal-to-noise ratio and thus reveal great potential for the application as biosignal recording electrode. In addition, low temperature fabrication process has potential application on flexible polymer substrates in the future.
The morphology and structure of 3D CNTs electrodes were observed by scanning electron microscope. The electrical properties of the 3D CNTs electrodes in PBS buffer solution were measured by electrochemical impedance spectroscopy (EIS). The capability of biosignal sensing of the electrodes was demonstrated through living organism Electrocardiology(ECG).

A key challenge in the development of functional bioelectronics is the need for a reliable and scalable approach to assemble biomolecules into electronic architectures, in particular at the individual molecule scale. Here we present a new method to interface individual biomolecules with carbon nanotube transistors, with robust covalent binding and an unprecedented 10-nm position resolution. Using high-resolution electron-beam lithography in a thin polymer layer, we pattern nanoscale openings over individual carbon nanotube devices, through which we perform covalent chemistry to attach localized grafts on the nanotube. Statistical analysis of hundreds of functionalized devices reveals a consistent electrical signature characteristic of a Poisson distribution with an average of 1.3 graft per device. Devices holding a carboxylic acid functional group are also found to present real-time two-state quantized fluctuations in the presence of a carbodiimide agent, a signature associated with single-molecule interaction. We finally report biofunctionalization of the initial grafts with individual DNA strands using an EDC/NHS coupling agent. This nano-confined chemistry approach forms a versatile and powerful method to integrate a variety of biomolecules into carbon nanotube electronic circuits.

Graphene, the well-known 2-dimensional honey comb lattice of sp² bonded carbon atoms, has seen vast applications in all forms of electronic processes due to its high carrier concentration and mobility.¹ It’s superb electronic properties presents graphene as a viable ultra-high sensitivity biosensor at the molecular level.² Graphene defects make binding to bio-specific markers possible, but increased number of defects impedes the electrical sensitivity within the graphene. An optimization between the defect concentration and electronic properties is needed to advance the practicality of a graphene biosensor.

Different concentrations of defects have been introduced into graphene sheets through the application of e-beam irradiation from a scanning electron microscope. The pressure was varied between experiments from high vacuum to low vacuum through the introduction of water vapor. The concentration of defects was characterized using the D to G intensity ratio in Raman spectroscopy in correlation with XPS studies. The characteristic bell curve of the D to G intensity ratio is present as the graphene shifts through the amorphization trajectory of graphene with increasing electron dosage.³ Binding studies between the e-beam irradiated graphene and amino acids is the preliminary study before understanding the binding of bio-specific markers can be achieved. Studying the phonon modes present in an interacted sample gives indications to what bonds are formed between the two. Electrical characteristics of the e-beam defected graphene gives information about the sensitivity it possesses with certain concentration of defects present. This research helps further indicate the practicality of an ultra-high sensitivity graphene biosensor.

References
1. Bolotin, K. I. et al. Ultrahigh electron mobility in suspended graphene. Solid State Commun. 146, 351–355 (2008).
2. Zhang, B., Li, Q. & Cui, T. Ultra-sensitive suspended graphene nanocomposite cancer sensors with strong suppression of electrical noise. Biosens. Bioelectron. 31, 105–109 (2012).
3. Iqbal, M. Z., Kumar Singh, A., Iqbal, M. W., Seo, S. & Eom, J. Effect of e-beam irradiation on graphene layer grown by chemical vapor deposition. J. Appl. Phys. 111, 084307 (2012).

This work describes the design and synthesis of amphiphilic silica nanoparticles for the stabilization of aqueous drops in fluorinated oils for applications in droplet-based biochemical assays. The success of droplet microfluidic techniques has thus far relied on one type of surfactants for the stabilization of drops. However, surfactants are known to have two key limitations: (1) the formation of surfactant micelles mediate an undesirable inter-drop molecular transport, which leads to the cross-contamination of droplet contents. (2) Surfactant-laden surfaces are incompatible with the growth of adherent mammalian cells as the liquid−liquid interface is too soft for cell adhesion.

The use of nanoparticles as emulsifiers to form “fluorinated Pickering emulsions” overcomes these two limitations. Particles are effective in mitigating undesirable inter-drop molecular transport as they are irreversibly adsorbed to the liquid−liquid interface. They do not form micelles as surfactants do, and thus, a major pathway for inter-drop transport is eliminated. In addition, particles at the droplet interface provide a rigid solid-like surface to which cells could adhere and spread, and are thus compatible with the proliferation of adherent mammalian cells such as fibroblasts and breast cancer cells. We further show that our fluorinated Pickering emulsions are also compatible with droplet-based enzymatic assays. The droplet surface is rendered nonadsorbing to proteins by introducing poly-ethylene glycol (PEG) to the aqueous phase. PEG adsorbs on the surface of nanoparticles in-situ and forms a biocompatible layer which minimizes non-specific adsorption of enzymes on particle surface. This strategy maintains both the activity of the enzymes and the accuracy of the assay as inter-drop transport is mitigated by the use of nanoparticles as emulsifiers. Given the unique non-leaky and nonadsorbing interfaces formed, the particles described in this work are expected to enable new opportunities for an increased range of biochemical assays. They have the potential to become a competitive alternative to current surfactant systems for the stabilization of drops critical for the success of droplet technology.

Polymer vesicles, or polymersomes, are being widely explored as synthetic analogs of lipid vesicles based on their stability, robustness, barrier properties, chemical versatility and tunable physical characteristics. Traditional methods to prepare giant polymersomes (>4 μm) are both time and labor intensive, yielding low numbers of intact polymersomes. Here, we present the rapid and high-yielding formation of giant unilamellar polymersomes using gel-assisted rehydration, and describe a mechanism of how formation and size distribution of polymersomes may be achieved. Using this method, polymersomes were formed from an array of polymer compositions, including a pH sensitive polymer, rendering polymersome formation reversible. Furthermore, polymersomes were successfully formed in a variety of biological rehydration solutions, including mammalian cell culture media. Likewise, polymersomes were able to successfully encapsulate biological materials, indicating that gel-assisted rehydration is a versatile method for building polymersome-based protocells. Polymersome size was easily tunable by altering temperature during rehydration or adding fluidizers to the polymer membrane, generating giant-sized polymersomes (>100 μm). The correlation between size and membrane fluidization suggests a unique mechanism from that proposed for giant lipid vesicle formation in which both polymer diffusivity and osmotic potential drive the formation and size distribution of the polymersomes. Overall, this technique is capable of reliably producing polymersomes from different polymer compositions and charges with far better yields and much less difficulty than traditional methods. Furthermore, vesicles formed in biological buffers and media and encapsulating biological materials make them readily useful for biomimicry studies.

Following the BRAIN initiative, there has been burgeoning interest in neuron-targeting colloidal nanomaterials for applications like imaging, drug delivery across the blood brain barrier, and vision restoration by optical stimulation. Designing the nano-bio interface for neurons presents three main design challenges: specificity, biocompatibility, and stability. Here, I will present surface modification strategies to tackle these design challenges for metal nanoparticles (NPs). I will present data on colloidal Ag nanoparticles modified with mixed ligand shells composed of polyethylene glycol (PEG) and charged carboxylic acid-functionalized alkanethiols. Our results indicate these mixed ligand shells increase NP stability against aggregation in Schneider Drosphila culture medium due to charge screening and steric repulsion. PEGylated mixed monolayers consisting of 5K, 10K and 20 KDa PEG chains showed increasing stability with increasing PEG size, as characterized by dynamic light scattering. Additionally, these mixed ligand shells encourage the formation of a protein corona upon NP incubation with bovine serum albumin. This protein corona thickness decreases with increasing PEG size and decreasing surface charge. We further tailor these NP surface chemistries for modification with anti-horse radish peroxidase to exhibit neuronal specificity in our model organism, Drosophila melanogaster.

In this study, we prepared poly(lactic- co -glycolic acid)(PLGA) nanoparticles loaded with bioactive materials such as EGCG and asiaticoside by using a W/O/W emulsion-solvent evaporation method for wound healing application.
In order to control and optimize the various parameters for nanoparticle formation, the experiments were investigated according to concentration of surfactant agent, stirring methods of composite solution, and water/oil phase ratio. The bioactive materials-loaded PLGA nanoparticles were evaluated for the particle size and distribution by SEM.
The sizes of particles and polydispersity(PDI) were determined by Dynamic Light Scattering(DLS). Particles containing bioactive drug were incubated in phosphate buffer saline solution at 37°C for vitro release profiles study. Drug encapsulation efficiency and concentration of drug on supernatant were determined by high-performance liquid chromatography. The release rate of bioactive materials were examined by UV-visible spectroscopy. Wavelength for drug quantification was selected at 248nm to 361nm.
As the results, the conditions that uniform and stable nanoparticles were formed were found out 0.7wt% PVA, 250W ultrasonic irradiation for 5 minutes and 1:10 water/oil phase ratio. PLGA the sizes of the particles were uniform sizes of 150~200nm and distributions of particle size was shown as monodisperse.
The application of bioactive materials-loaded PLGA nanoparticles of our study will be useful for the therapy of diabetic foot ulcer and wound healing.

Passive diffusion of drugs and reagents across the cell’s plasma membrane barrier is an inefficient and poorly controlled process, despite its fundamental importance to biotechnology, cell biology, and pharmaceutics. In particular, the fundamental requirement for membrane permeability frequently limits the accumulation of drugs in the cytoplasm, undermining drug efficacy and over-constraining drug design. In contrast, gap junctions, transmembrane protein channels that physically connect the cytoplasm of adjacent cells, bypass the plasma membrane, permitting a diverse range of molecules to move rapidly from the cytoplasm of one cell to the next, from ions and metabolites to siRNA and chemotherapeutics. Our work aims to address the challenge of crossing the plasma membrane barrier by using the cellular gap junction network to deliver drugs directly to the cytoplasm of tumor cells. Specifically, we have developed Connectosomes, cell-derived lipid vesicle materials that contain functional gap junction channels and can form gap junction interfaces with cells. We formed Connectosomes by harvesting plasma membrane vesicles from donor cells that were engineered to overexpress gap junction channels. These novel materials transferred small molecules, including fluorescent dyes and chemotherapeutics, directly to the cellular cytoplasm. Remarkably, using Connectosomes to deliver the chemotherapeutic doxorubicin reduced the therapeutically effective dose of the drug by more than an order of magnitude. These results demonstrate the potential of Connectosomes to substantially increase the efficiency of molecular transport into the cytoplasm. This increase in efficiency has the potential to boost the effectiveness of existing drugs, such as chemotherapeutics, helping to address long-standing problems such as dose-limiting toxicity and multidrug resistance. Further, in bypassing the plasma membrane barrier, Connectosomes remove a key constraint on therapeutic design, enabling the development and delivery of membrane-impermeable drugs and reagents.

Graphene oxide have been widely explored in biomedical applications as active engineered materials for diagnosis and therapy. With the great potential of using these nanocomposites in biological systems, such as in the manufacture of small materials for biotechnological application, it is very interesting to understand with details how these materials interact at the molecular level with cell membranes in living systems. In this study we investigated the interactions between graphene oxide and cell membrane models using the technique of vibrational sum frequency generation-SFG spectroscopy, specific for interfaces. The membrane models comprised Langmuir phospholipid monolayers composed by DSEPC (1,2-distearoyl-sn-glycero-3-ethylphosphocholine chloride satl), DSPC (1,2-distearoyl-sn-glycero-3-phosphocholine) and DSPA (1,2-distearoyl-sn-glycero-3-phosphate sodium salt). The interaction between the graphene oxide and the membrane models was revealed via SFG as the decrease in the CH₃ band at 2880 cm^-1 in comparison to the band at 2942 cm^-1. The investigation of the interactions between nanomaterials and membranes using SFG may be relevant for nanotoxicological studies.

Covalent conjugation of poly(ethylene glycol) called PEGylation is a well-known stealth method in vivo, for increasing availability of administered protein/peptide drugs in blood. PEGylation significantly decreases immunogenecity and renal clearance. Tethering target moieties at the end of PEG also enhances the therapeutic effects by targeted drug delivery. However, the covalent modification accompanies uncontrollable chemical reactions, attaching functional moieties to the unpredicted amino acid sites that irreversibly result in the loss of biological activity. Moreover, any types of chemical modification to therapeutics are subject to FDA approval procedures because they are classified as a new drug. Thus, reversible modifications of protein/peptide therapeutics have been regarded as an ideal strategy, but methods developed so far have been unreliable. In this study, we report a reversible protein modification method called TANNylation (Tannin and ~ylation) inspired by the adhesive properties of tannic acid, the well-known polyphenols found in plants. The TANNylation exhibits dual functions, enhancing half-life of the modified therapeutics in blood as well as increasing a unique tissue targeting to the ‘heart’. Green fluorescence protein (GFP) is chosen as a model protein for visualization and in vivo monitoring of the TANNylated GFP. We found that there is a stoichiometric window for the stable, reversible TANNylation. The reversible binding properties between tannic acid and proteins result in complete recovery of the TANNylated protein without losing any biological activity. The TANNylation protein interestingly provides an unexpected in vivo characteristic: robust adhesion onto the inner wall of the heart. Subsequently, the adhered TANNylated proteins are released from the heart surfaces. This interesting heart surface adhesion is originated from the interaction between tannic acid and the extracellular matrix protein, particularly elastin, which is abundant in aorta and heart valves. Our study indicates that TANNylation can be reversible as well as functional bio-interfacial modification strategy that can increase in vivo stability (i.e. improvement of therapeutic efficacy) and result in utilizing the heart as a new reservoir for controlled release of the proteins.

Neural stimulation is an essential technique for restoring lost neural functions and correcting diseased neural circuits. Conventional electrode-based electrical neural stimulation is usually limited by the strong attenuation of electric fields through tissues and thus often requires surgical placement of the electrodes in an intimate contact to the target neural tissue. Non-invasive neural stimulation techniques simply using an (electro)magnetic, light or ultrasonic field are, however, constrained by a poor spatiotemporal resolution. To pursue a minimally invasive neural stimulation technique with a significantly improved spatiotemporal resolution, we explore nanomaterials as mediators to convert a wirelessly transmitted external signal to a localized secondary stimulus at the nanomaterial-neural interface. Specifically, we focus on acoustic waves for their capabilities of deep tissue penetration and spatial focusing at sub-millimeter resolution. We thus employ piezoelectric zinc oxide nanowires to transduce the radiated acoustic energy to an electric field at the nanomaterial-neural interface. We hypothesize that the acoustoelectrically transduced electric fields at the nanowire tips will excite an intimately contacted neuron via activating voltage-gated membrane ion channels (primarily sodium channel) at the points of contact. We set out to test this hypothesis using dissociated rat hippocampal neurons cultured on a zinc oxide nanowire array. We synthesize biocompatible piezoelectric zinc oxide nanowire arrays of a high aspect ratio using zinc nitrate hexahydrate and hexamethylenetetramine as precursors and ammonium hydroxide to control the nanowire growth. We then characterize: (1) the morphology of these nanowire arrays using a scanning electron microscope, (2) the acoustoelectric transduction at the nanowire array surface using chemiluminescence for electric field imaging, and (3) the neuronal stimulation feasibility using calcium imaging. Furthermore, we tune the parameters of the ultrasonic pulses to match properties of the nanowire array in order to achieve a vibration resonance of the nanowires for an optimal acoustoelectric transduction. This technique of acoustic neural stimulation through piezoelectric zinc oxide nanowires promises as a minimally invasive approach with a high spatiotemporal resolution for numerous applications in neuroscience research.

A sealed microwell with a lipid bilayer membrane (LBM) is a promising candidate for constructing artificial cells. If membrane channels can be incorporated into the LBM, their functional properties can be detected. We have fabricated microwells sealed with LBMs on a Si substrate, and succeeded in observing Ca²⁺ transport through α-hemolysin channel with fluorescent microscopy [1]. However, ion leakage from/into a microwell poses a problem when we try to detect a channel current, which is of a similar order to the background noise. In this study, we investigate the effect of ion leakage from/into a microwell using differently charged LBMs, where we control the electrostatic interaction between the LBM and the substrate. We also describe a possible ion leakage mechanism in the microwell device.
We fabricated microwells (2-4 μm diameter) on a SiO₂ substrate with a lithographic technique. The microwells were filled with Ca²⁺ indicators (fluo-4) and then sealed with neutral LBMs by rupturing giant unilamellar vesicles (DPhPC:Cholesterol = 8:2). When Ca²⁺ ions were added to the outer solution, fluorescent images showed that the microwells at the edge of the lipid bilayer patch become bright after 5-15 min, whereas those at the center remained dark. This result indicates that there is an inflow of Ca²⁺ into the microwell, even in the absence of a membrane channel. It has been reported that the lipid bilayer is separated from the surface by a thin water layer. The Ca²⁺ ions are likely to pass through the water layer from the outer boundary of the lipid bilayer patch. To further examine the ion leakage mechanism, we investigated the dependence of the ion leakage property on the charge of the LBM. We employed DPhPC:Cholesterol:DOPS = 7:2:1 as an anionic membrane and DPhPC:Cholesterol:EDOPC = 7:2:1 as a cationic membrane. From the anionic membrane, ion leakage behavior was observed after 0.5-3 min, which is faster than that for a neutral membrane. On the other hand, fluorescence was not observed from the cationic membrane, indicating that there was no ion leakage. We speculate that the electrostatic interaction between a negatively charged SiO₂ surface and a charged LBM affects the thickness of the water layer. Namely, the electrostatic repulsion from the anionic membrane makes the water layer thicker leading to increased ion leakage. In contrast, the cationic membrane causes electrostatic attraction with the substrate surface and this leads to the suppression of ion leakage. We also consider another possible ion leakage mechanism whereby the charge of the LBM causes the cation concentration to vary within the water layer. This is to maintain the local electrostatic balance. The results reported in this study will enable us to improve the device properties without unfavorable ion leakage and lead to a methodology for the sensitive analysis of membrane channel on a Si substrate.
[1] K. Sumitomo et al., Biosens. Bioelec., 31, 445 (2012).

The chitosan is a biopolymer obtained from the exoskeleton of crustaceans. In this work we carried out an experimental study of chitosan solutions with different molecular weight and multiwalled carbon nanotubes (MWCNT). The characterization of the system we used Raman and UV-Vis spectroscopy, AFM and linear rheology. The Raman spectra show us the vibration of the grid and UV-Vis give us the optical properties and the effect of different molecular weight from chitosan in the system. AFM was used for the morphological study of chitosan and MWCNT interactions. Finally using rheology we study the correlation of the linear rheological properties of solutions of chitosan and MWCNT to determine the effect of molecular weight of the biopolymer on the viscoelastic modules varying the temperature of the medium as physico-chemical parameter of control.

The β-cyclodextrin_graphite oxide_carbon nanotubes (βCD_GO_CNT) composite was synthesized by a simple chemical method and characterized for the supramolecular recognition by using the cyclic voltammetry and differential pulse voltammetry. Three kinds of biomolecules (dopamine, thioridazine, L-tyrosine) were used, and βCD_GO_CNT composite presented excellent supramolecular recognition capability to the biomolecules compared to individual CNT and βCD_CNT composite, exhibiting the presence of GO in the βCD_GO_CNT composite could immobilize βCD molecules effectively. It is, therefore, demonstrated that new composite, βCD_GO_CNT, provides synergistic effect of high electric conductivity from CNT and high supramolecular recognition capability from βCD effectively immobilized in GO for future biosensor applications.

One-dimensional (1D) and two-dimensional (2D) carbon nanomaterials such as single-walled carbon nanotubes (SWNTs) and graphene have received great attention due to their remarkable electrical and physical properties. The demonstration of synthesizing these carbon nanomaterials has been progressed by chemical vapor deposition process on metallic surfaces which is inexpensive and robust way to produce high quality of carbon nanotubes and sheets of graphene. In addition, the exfoliation of graphite with strong oxidants has been explored to prepare a suspension of individual two-dimensional (2D) graphene oxide (GO) nanosheets dispersed in various types of solvents. Thus, this colloidal suspension of GO can readily be employed in a wide range of promising potential applications such as transparent electrodes, solar cells, optoelectronic devices and biological sensors. To fully utilize this material, one major challenge is to assemble such individual nanosheets on defined areas of surfaces forming specific structures. Thus far, a variety of techniques such as Langmuir-Blodgett assembly, vacuum filtration, dip-coating, spraying, and spin- casting process have been developed to allow the formation of carbon nanostructures at the micro and nanoscale.
Here, we describe a simple and facile one-step process to achieve patterned arrays of chemically reduced graphene oxide (rGO) on a substrate with precisely controllable manner over large areas. The spatial positioning of rGO on a certain surface still remains challenging since the originally synthesized GO nanosheet has high aspect ratio with different length scale i.e., single atomic scale in thickness and micrometer scale in lateral size. By confining a drop of rGO solution in a restricted geometry, two different types of self-organized rGO patterns e.g., concentric ring patterns and spoke-like strip patterns were fabricated on glass and SiO2/Si substrate through a combination process of coffee-ring effect and cyclic stick-slip motions by solvent evaporation. Interestingly, these carbon nanomaterial platform can be used as temporary scaffolds or promote the reorganization of the cells to form a functional tissue. Thus, to utilize these carbon nanostructures as a cellular matrix, we evaluated the biocompatibility and biofunctionality with L-929 fibroblastic cells and PC-12 neuronal cells, respectively. The examined results suggest that graphene-based substrates as biomimetic cues have good biocompatibility as well as a unique surface property that can enhance the neural cells, which would open up some opportunities in tissue regeneration and nanomedicine.

Electrospun nanofiber mats were used to scaffolds for tissue engineering of vascular structures, bones, and nervous systems. Also, the similarity to the fibrous structure of natural extracellular matrix has advantages in that electrospun nanofiber mat has wide accessibility to fibers made of polymers, ceramics and metals. The nanofiber scaffolds, however, have trouble with some problematic issues. There are small pores between fibers that regulate cellular infiltration across the nanofibers, and two-dimensional fiber mats which prevent the preparation of scaffolds moldable into three-dimensional shapes for fitting in target. To realize them, three-dimensional fibrous scaffolds with deformable properties were fabricated by dual-nozzle assisted electrospinning polystyrene and polycaprolactone and selective removing. PCL fibrous structure that remained after removing polystyrene have highly moldable characteristics like clay with high porosity. Therefore, the PCL scaffolds could be molded to any other form, and highly favorable for cell expansion. These electrospun clay-like scaffolds overcome the problems of conventional sheet-like electrospun scaffolds, which are structurally inflexible. So, this work expands the scope of electrospun fibrous scaffolds toward a diversity of tissue engineering applications.

Self-assembled viral protein cages like the cowpea chlorotic mottle virus (CCMV) are widely used in material sciences, medicine and catalysis. These particles are symmetrical and monodisperse, have the ability to encapsulate functional cargo and have been decorated with a variety of drugs, fluorescent dyes, polymers and carbohydrates. CCMV is an icosahedral plant virus consisting of 180 identical coat proteins that self-assemble around the viral RNA. The spherical capsid is 28 nm in diameter and has a Caspar and Klug triangulation number T = 3. A particularly interesting feature of CCMV, is its defined and reversible assembly behavior. Depending on pH and ionic strength, CCMV can disassemble into coat protein dimers and reassemble into non-infectious virus-like-particles (VLP). This makes it possible to use CCMV as an encapsulation vesicle. Here we report on the immobilization of CCMV on CB[8] monolayers via the formation of a heteroternary complex between CB[8], azobenzene and methyl viologen. To this end, the outer surface of CCMV was functionalized with alkyne moieties and post-functionalized via click chemistry with an azobenzene switch, resulting in the immobilization of the VLP's in a dynamic supramolecular fashion. This surface engineering may open new routes to study multi-valent, biologically relevant interactions.

Nanoparticles (NPs) have been used to inhibit or modulate the peptide fibrillation kinetics as a potential strategy for treatment and to understand the molecular mechanisms of amyloid diseases, benefiting from the large surface area and tunable surface properties.^[1] Islet amyloid polypeptide (IAPP) is a 37 amino acid peptide hormone co-secreted with insulin from the pancreatic islet. Overproduction of IAPP during hyperinsulinemia involves in islet beta-cell failure featured for type II diabetes (T2D) pathogenesis, by triggering ion channel formation and nonspecific disruption of cell membranes, and catalysing fibrillation of such amyloid peptides.^[2] In this work, we discovered the strong interactions between bare gold NPs (AuNPs) and IAPP due to the presence of metal-binding amino acid sequence at the hydrophilic peptide domain. Molecular Dynamics (MD) simulation suggested that the binding of IAPP onto the Au surface was initiated by the N-terminal region, followed by an induced conformational change of IAPP in a facet-dependent manner. Circular dichroism (CD) and transmission electron microscopy (TEM) showed the fibrillation process of IAPP in solution was accelerated by AuNPs, where large particles displayed a stronger effect in promoting IAPP fibrillation than smaller ones. This effect may originate from AuNPs-accelerated conformational change of IAPP from random coil to helix. On the other hand, the IAPP-NP interaction could reduce the cytotoxicity of IAPP oligomers by preventing the lipid membrane disruption with AuNPs. We anticipate this work will shed a light on the understanding of the mechanism of IAPP fibrillation and IAPP-NP interactions, and also provide a possible tool for amyloid relevant disease treatment.


[1] a) P. D. Howes, S. Rana, M. M. Stevens, Chem. Soc. Rev. 2014, 43, 3835; b) S. Eustis, M. A. El-Sayed, Chem Soc Rev 2006, 35, 209; c) P. D. Howes, R. Chandrawati, M. M. Stevens, Science 2014, 346, 1247390.
[2] a) M. F. M. Engel, L. Khemtémourian, C. C. Kleijer, H. J. D. Meeldijk, J. Jacobs, A. J. Verkleij, B. de Kruijff, J. A. Killian, J. W. M. Höppener, Proc Natl Acad Sci U S A 2008, 105, 6033; b) J. R. Brender, E. L. Lee, M. A. Cavitt, A. Gafni, D. G. Steel, A. Ramamoorthy, J Am Chem Soc 2008, 130, 6424.

The multimodal biomedical applications are still seeking for new nature-inspired biocompatible carriers. Herein we present magnetic and fluorescent microcomposites for potential use in drug delivery, hyperthermia and medical imaging. Such materials are based on glucan polysaccharide microparticles (GPs) derived from baker's yeast. Microbial glucan shows high affinity towards immune system and ability of its activation. These magnetic composites were synthesized by in situ precipitation method in the presence or absence of capping agents, when GPs were acting as microreactors. Their surface morphology was characterized with SEM. Stability of dispersed particles, particle size distribution and its evolution within a time was measured on a coulter counter and with a static light scattering. SAR numbers for the different composites were calculated from the data observed from exposure to RF-field (400kHz, 20mT) and relaxation times for these materials were measured on a MRI. Fluorescent polysaccharide was prepared via isothiocyanate chemistry of the dye and the whole system was visualized by confocal microscopy. The theranostic potential was tested on the culture of macrophages in vitro, in an ex vivo planar tissue model.

In recent years, innovative nanomedical technology to meet unmet needs of medicine is advancing rapidly, and therefore the importance of nanobioparticles with 10-100 nm diameter is icreasing more and more. Here, nanobioparticels include both artificial or biologically-originated nanoparticles functioning in vivo. For example, nanoparticle carriers that can deliver drugs or genes to a specific target site are going to be put to practical use before long and cell-secreted nanovesicles such as exosomes and microvesicles are intensively studied toward their clinical application as biomarkers.
However, absence of adequate tools for analyzing and/or identifying mesoscopic-sized particles ranging from tens to hundreds nanometers is the potential obstacle in both fundamental and applied studies of nanomedicine, and hence, there is a growing demand for a novel analytical method of nanoparticles with good reproducibility and ease of use.
In this presentation, we will present an analytical platform for nanoparticles, which allows particle immunoelecrophoresis on a microfluidic chip, mainly focusing on the background of the development and technological outlines. The developed platform allows detection of individual nanoparticles or nanovesicles of less than 50 nm in diameter and enables the characterization of nanoparticles based on indexes such as concentration, diameter, zeta potential, and surface antigenicity.

We have been proposing a biological process to fabricate device key nanostructures by protein supramolecules”, which we named “Bio Nano Process” (BNP)1,2). In the BNP, protein supramolecules work as templates for the biomineralization of homogenous nanoparticles(NPs)/nanowires(NWs). The biomineralization covers a wide variety of inorganic materials from conventional bio-related materials to artificial inorganic materials. We have been expanding the proteins’ biomineralization capabilities by genetic modification, and now can synthesize NP/NW of metal-complex and/or semiconductor materials using mutant protein supramolecules3). The surfaces of protein supramolecules are further modified chemically or genetically to make them self-organize into functional nano-structures at designated parts of the substrates. One typical example is a two dimensional crystalline array of cage-shaped protein with NP 4). The processes are carried out in the aqueous condition under room temperature. No toxic organic solvents are necessary, which means that the BNP is intrinsically eco-friendly.
We have already designed and produced several kinds of protein supramolecules for the BNP and applied them to produce key components of nanodevices, such as a floating nanodot gate memory (FNGM), a single electron transistor, a Re-RAM, quantum solar cell, bio-sensors, Single Nucleotide Polymorphism (SNP) sensing LoC, dyes-sensitized solar cell, thermo-electronic device, and other electronic devices 2,5,6).[1] I. Yamashita, Thin Solid Films, 393, 12-18, (2001). [2] I. Yamashita et. al., Biochimica et Biophysica Acta, 1800, 846-857, (2010), [3] K. Iwahori et. al., Mat. Lett. 160, 154-157, (2015), [4] R. Tsukamoto et. al., Appl. Phys. Express, 5, 065201 (2012), [5] I. Inoue, et. al., ChemsusChem. 7(10), 2805-2810, (2014). [6] M. Ito, et. al., Appl. Phys. Express, 7, 065102 (2014).

In nature, photosynthetic reaction centers (RC) transduce solar energy into chemical redox energy with a quantum efficiency near unity. Rhodobacter (Rb.) sphaeroides RC has been well characterized due to its simple, robust structure. It has previously been attached to electrodes to generate photo current in none-bio environment by direct monolayer deposition of RC¹. This method is only suitable for the electrode with small surface areas since there is no interaction between the RC and electrode. The photo current is only nA/cm² range due to the limited electrode surface area. In order to get large photo current, a material which can interact with multiple layer is great in demand. Herein, we successfully incorporate a transparent and porous antimony-doped tin oxide (ATO) thin film with multiple layers of RCs via Cytochrome c. RC proteins are likely to be oriented on the ATO surface in such a way that the electron-accepting ‘P’ end faces the ATO surface and can directly receive electrons from Cty c sandwiched between the RC and ATO. By taking advantage of the multiple layers of RC and large electrode surface area, we can get a photocurrent density of 2 μA/cm². The action spectrum confirms that RC is responsible for the observed photocurrent. Electrochemical characterizations indicate the critical role of Cytochrome c for the effective electron transfer between the RC proteins and the inorganic ATO surface. Details of the nano/bio hybrid fabrication and characterization will be described in context of light-harvesting photoelectrochemical applications.

Reference:
1. Mahmoudzadeh, A et al (2011) Photocurrent generation by direct electron transfer using photosynthetic reaction centres. Smart Mater. Struct. 20 094019

Two-dimensional materials such as graphene oxide (GO) and its derivatives are highly desirable for biomedical sensing applications, owing to their high surface area, unique optoelectronic properties and a broad spectrum of functionalization chemistries. However, in order to be deployed successfully in sensing devices, such as those used for cell capture, it is important to be able to engineer the physico-chemical landscape of the distribution of the functional groups in GO, and consequently tune the material properties at the nanoscale. Till date, most applications have either used as-synthesized GO directly - without an exploration of the benefits of the oxygen framework, or by reduction to reduced graphene oxide (rGO) - with inferior optoelectronic properties. In this work, we present a novel, one-step, mild thermal annealing process to control the sheet properties of graphene oxide, in a scalable manner, without the use of chemical treatments. Using a combination of direct and indirect evidence, coupled with atomistic simulations, we demonstrate that the underlying structural transformation is effected by a phase separation of the mixed sp²-sp³ hybridized phases into distinct oxidized and graphitic domains, with the diffusion-mediated process accelerated by thermal energy provided during annealing. Further, we utilize this pre-treated GO to construct an elegantly simple, yet highly sensitive planar cell-capture device, for quick and efficient capture of cells from whole blood, without the need for additional process steps to separate other components of the plasma. Using nanobodies decorated on our pre-treated GO through a sortase-mediated click chemistry functionalization approach, we report an enhancement in the cell capture efficiency up to 92 ± 7%, compared to only 54 ± 3% in conventional devices made using as-synthesized GO without applying our annealing pre-treatment. We attribute this enhancement to a higher surface functionalization density of the nanobody on the GO substrate, as a result of the clustered oxygen domains formed by annealing. These results potentially open up a whole new class of low-cost diagnostics based on GO substrates, suitable for deployment in rural areas and in emerging countries with lack of access to advanced healthcare.

Circulating tumor cells (CTCs) from peripheral blood hold important information for cancer diagnosis and disease monitoring. However, detection and isolation of CTCs has been technically challenging due to the extremely low abundance of CTCs among a large number of hematologic cells in the blood. Microfluidics-based technologies is one of the most often used method to improve the capture efficiency by enhancing the cell-substrate contacts frequency. Recently, it also have been demonstrated that nanostructure of substrate could improve the capture and isolation efficiency of CTCs significantly. Here we report an effective strategy for capturing CTCs based a patterned silicon pillar microfluidic device with surface modified TiO₂ nanorod array. Firstly, we demonstrated the high adhesion preference of cancer cells to antibody modified TiO₂ nanorod array compared to other cells on the TiO₂ nanorod array modified silicon. The capture efficiency of cancer cells was significantly improved by TiO₂ nanorod array compared to smooth silicon. To further improve the capture efficiency, a layer of TiO₂ nanorod array was modified on the surface of patterned silicon pillar array microfluidics devices. After flowing through the microfluidics devices, cancer cells was successfully captured and isolated from blood samples by the TiO₂ nanorod array modified silicon pillars in an efficient way.

It has been found that the nanopillars on cicada wings are inherently antibacterial, irrespective of surface chemistry (Ivanova et al., Small, 2012). Application of these nanopillars to consumer polymer surfaces would result in inherently antibacterial polymer surfaces without use of antibiotic drugs or biocide chemicals. Nano- and microstructured antibacterial surfaces have been previously proposed, including the Sharklet microstructured film (Chung et al., 2007), black silicon (Ivanova et al., 2013) and multi-scale wrinkled polymer films (Freschauf et al., 2012); none of these approaches can be used on ordinary polymer surfaces or easily scaled up. Thus, we applied industrial polymer nanostructuring techniques to generate biomimetic antibacterial nanostructures at the surfaces of poly(methylmethacrylate) (PMMA), a material commonly used in medical devices, particularly in ophthalmologic applications. We employed nanoimprint lithography, an industrially viable fabrication process, to produce our nanostructures. We utilized several molds for our process: nano-holed (negative) molds (Lightsmyth), a commercially available nickel antireflective nanopillar (positive) mold (Holotools, Germany), and a black silicon nanopillar (positive) mold we fabricated using reactive ion etching. We treated these oxide surfaces with a fluorinated silane (perflurodecyltrichlorosilane) using molecular vapor deposition to apply a release coating. These molds were used to fabricate PMMA nanopillar arrays directly from the negative molds, or to generate polydimethylsiloxane nanohole arrays from the positive molds to be used for subsequent PMMA nanopillar molding. The replication processes resulted in large, flat PMMA nanopillar arrays. Compared to flat films, PMMA nanopillar arrays 1) exhibited reduced surface adhesion of live E. coli determined by a standard fluorescence based viability assay, and 2) killed these bacteria, as evidenced AFM and SEM showing punctured bacterial cells on nanopillar arrays (Dickson, Liang, et al. 2015). Recent efforts have focused on optimizing the bactericidal performance of pillars to assess effectiveness against gram-positive bacteria. Our surfaces could be used for a wide variety of environmental and medical applications, including surgical trays / instruments and door handles (which function in air), and for implantable medical devices or catheter tubes (which function in aqueous environments).

Current detection techniques in food safety and water quality monitoring, such as culturing and GC/MS, are relatively slow, require bulky instrumentation, are costly to perform, and usually require some form of specialized training. Therefore, simpler detection techniques that are both fast and sensitive could greatly improve detection and identification for a variety of targets in environmental monitoring. Label-free biosensors that combine high sensitivity and high specificity characteristics have shown tremendous potential for such applications. A unique type of label-free, optical sensor, based on Whispering Gallery Mode microresonators, has tremendous potential to revolutionize biodetection due to its extreme sensitivity. The primary limitation of these devices, however, is that they require the addition of biorecognition elements to specifically target a biological species of interest. Therefore, the ability to selectively functionalize the microresonator for a specific target molecule, without degrading device performance, is extremely important, and represents the next step in translating these devices from laboratory to field environments. While this can be accomplished via traditional surface chemistry, a simpler alternative is the application of size- and shape-selective nanostructured, porous thin films as surface coatings. These materials, including polymeric sol-gel materials like microporous, mesoporous, and molecularly imprinted materials, offer high selectivity and a range of physico-chemical properties that may be more useful and flexible than traditional deposition of recognition elements like antibodies, proteins, etc., which can suffer from poor performance when attached improperly to the surface.

Here, we discuss a variety of straightforward nanostructured, porous materials that could be used to impart specificity or selectivity to optical microresonators, but also allow for the creation of multi-use platforms for complex environments. Of particular interest with these materials is their basic optical properties, such as index of refraction, absorption, vibrational spectra, and emission spectra, as these govern their potential application to optical sensors. Moreover, their ability to interface with their environment determines their productivity as recognition elements. We will discuss the synthesis, optical properties, and biocompatibility of two thin film materials that can be used to coat WGM optical microresonators: pure-silica zeolite MFI, and pure-silica mesoporous materials. By combining these high sensitivity sensors with appropriate material systems, the resulting platforms can be extended to address broader issues in environmental biosensing that directly impact food and water quality.

The need to develop sensory platforms that identify targeted chemicals in a highly sensitive and selective manner is a pressing demand with respect to public health, environmental monitoring and national security. Nature has been provided a great inspiration for the design of sensitive and selective sensors. The mammalian olfactory system, often characterized amongst the most powerful sensing platforms in nature, stands as a prime example with its impressive detection range, high sensitivity, and accurate chemical discrimination. These emergent characteristics are due in part to the fact that just one chemically distinct odorant activates multiple receptors, generating spatial patterns of activation at the olfactory glomerular layer, allowing for detection and discrimination amongst a variety of odorants. Recently, we have demonstrated that genetically modified peptide receptors expressed in M13 bacteriophage, and its corresponding hierarchical phage color film can be utilized as a colorimetric responsive bioanalytical platform. Inspired by the pattern recognition of the olfactory system, we have constructed arrays of phage-based thin films as cross-responsive platforms for artificial nose type pattern recognition. Foremost amongst our most recent efforts has been the design of phage arrays, cross-responsive platforms fabricated with the deposition of rationally selected genetically modified phage and engineered 3,4-dihdroxy-phenylalanine phage on transition metals. These arrays have successfully been used to generate molecular recognition patterns that further our engineered sensory system’s sensitivity and selectivity. Fabrication of phage color sensor arrays employs 5 uniquely engineered phage films and 5 different pulling speeds. With this multiple component phage array, a molecular recognition colorimetric pattern is generated for each analysis. The resulting color difference profiles exhibit a unique “molecular fingerprint” for each gas analyte over similar chemical vapors. To evaluate the variation between responses from multiplexed analysis, principal component analysis is used to determine the dimensionality of sensor array data. PCA analysis is performed to create linear combinations of the array’s responses, maximizing the total discriminating ability amongst the data in as few dimensions as possible.

The advancement in the biosensor technology has facilitated the detection and quantification of relevant biomarkers that are associated with different health conditions and are of interest in the assessment of a patient’s well-being. Here, we demonstrate a design, fabrication and characterization of label-free plasmon-based biosensor consisting of about one billion metallic nanocup arrays with a sub-wavelength opening covered with metal nanoparticles on the side walls of nanocups. This nanocup array substrate achieves refractive index sensing through a transmission peak shift with the extraordinary transmission phenomena. The sensor device is fabricated by thin film semiconductor material such as cadmium sulfide (CdS) layer, which has high refractive index (n~2.53) and very low extinction coefficient, sandwiched between two Au layers. The Au-CdS-Au nanocup array structure allows sensing based on the transmission intensity change with the help of simple bandpass filter to allow certain wavelength to be transmitted in a visible region at normal incidence illumination. Due to the high refractive index of the sandwiched layer, CdS thin film which acts as a resonant cavity, electric field is confined at the interface of Au and CdS layer at lower surrounding refractive index. An increase in the surrounding refractive index causes a decrease in the electric field intensity at the interface but an increase in out-coupling of electric field on the topmost Au layer, hence, enhancement in overall transmission intensity is observed. The Au-CdS-Au nanocup array substrate, in addition, shows a great performance in detecting DNA hybridization and the antibody-antigen interaction.

State-of-the art neuromodulators are bulky, and they are mostly fabricated on rigid substrates. Furthermore they are not provided with a feedback control loop, resulting in undesired off-target effects. We demonstrate lightweight hybrid optical-electrical system with the capability to implement closed-loop controlled neuromodulation down to a single cell resolution. Our devices allow neurons to live in an environment which is closer to their natural microenvironment, i.e., compliant and 3D. They can implement control of neural activity with high signal-to-noise ratio, high specificity and high spatio-temporal resolution (as they use optical signals). Our fabricated hybrid optical-electrical systems are based on device grade inorganic thin films, i.e., nanomembranes (NMs), formed in ordered arrays of buckled channels on compliant substrates. The buckled NMs include light-emitting structures in the visible range (namely Si nano-crystals) and graphene electrodes to control and record neural activity, respectively. The compliant substrates of choice is polydimethylsiloxane (PDMS). Buckled NMs are obtained by guided self-assembly of the supported thin films under compressive strain. The cross-sectional size of buckled NM channels is scaled to match the dimensions of single neurons. In our work, a fabrication process based on multiple layer release and transfer enables graphene electrodes to be fabricated on the inner side of the buckle-delaminated channels. We present structural characterization of the fabricated devices, along with I-V characteristics of the graphene electrodes, and photoluminescence measurements to assess the optical emission of the buckled NM.

The development of methods for the conformal and seamless implementation of electronics on biological surfaces has great importance for biomedical, biological, bionic and energy applications. However, there are material and mechanical challenges associated with interfacing traditional electronic materials with biological materials. Alternative approaches are required for the efficient and versatile merging of electronics with biological surfaces. Here we introduce an effective approach using 3D printing with 3D scanning to realize the objective of implementing printed electronics conformally on biological surfaces. A variety of materials can be used in 3D printing for fabricating electronics. Here, silver nanowires (AgNWs) were chosen, due to their excellent and controllable electrical conductivity, and ability to mechanically sinter under mild conditions. The AgNWs were initially synthesized via reducing silver nitrate (AgNO₃) by glycerol in the presence of poly(vinyl pyrrolidone) (PVP). In order to improve dispersion homogeneity of AgNWs in solvent, 16-mercaptohexadecanoic acid was added to modify the surface of the AgNWs. The modified AgNWs were characterized and their average diameter and length were 50 nm and 5 μm, respectively. Next, the modified AgNWs were mixed with compliant polymers in a proper solvent to form 3D printing inks. A shear force mixer and powerful ultrasonicator were applied on the inks to ensure that the inks were homogenous and printable. The resistances of the printed inks can be controllable through mechanical sintering and/or by changing the printing volumetric flow rate. The results indicated that the alignment and uniformity of AgNWs in a polymer resin would significantly influence the electrical properties of the ink. Finally, a biological surface, such as an insect shell or animal skin, was scanned via a 3D scanner to obtain the detail of their topology, for the purpose of successfully printing and implementing electronics conformally on the biological surface. As a proof of concept, we directly printed a AgNW-based capacitive sensor on an insect wing. The capacitance of the sensors changed linearly during the flapping of insect wing. This results from the resistance change of the sensors during mechanical deformation. These results illustrate, for the first time, the seamless 3D scanning and printing of functional electronics conformally on a biological surface for measuring the motion of a biological living subject.

Cell membranes contain versatile membrane proteins such as olfactory receptors and ion channels which play critical roles in various cell activities. For example, olfactory receptor proteins can bind only to specific odorant molecules, which allows our olfactory systems to distinguish different smells. In this presentation, we will discuss how to interface membrane proteins with carbon nanotube networks to build versatile functional devices. As one example, we will report bioelectronic nose devices based on olfactory receptor protein-carbon nanotube hybrid structures. Furthermore, we will also describe how one can interface carbon nanotube network-based devices with the cell membrane of a cell to monitor the drug responses of the cell.

In the rapidly advancing field of bioelectronics the organic electrochemical transistor has proven an interesting candidate for interfacing with biological environments. It has been used to monitor living cells (Ramuz, M. et al. Adv Mater 26, 2014), detect metabolites (Strakosas, X. et al. J Mater Chem B 2, 2014) or record brain activity (Khodagholy, D. et al. Nature Comms 2573, 2013). However, in long-term measurements one often faces problems with a non-linear background arising from evaporation, temperature drift and/or charged species other than the analyte in the electrolyte. More specifically, blood as a complex medium severely interferes with the precise detection of metabolites, such as glucose or lactate, making it difficult to obtain quantitative result.

To circumvent this issue, we use a reference-based sensor circuit, by integrating electrochemical transistors based on the conductive polymer poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate into a Wheatstone bridge layout. Using one transistor as a reference sensor and another one as a sample sensor, we can provide a signal-ON response contrary to a single transistor sensor, by differentially measuring the voltage drop across each transistor. By carefully choosing the appropriate operation point of the transistors, we obtain a good amplification of the input signal, thus enhancing the overall sensitivity of the device.

Optimizing the biofunctionalisation scheme at the sample transistor, one can immobilize different biorecognition elements, thus targeting different analytes and applications. In this work we provide a selective in-vitro biosensing platform aiming to target specific analytes of interest in complex media (i.e. glucose, cholesterol and lactate). With this device and an in depth understanding of its function, a versatile point of care diagnostics platform is developed, allowing for more accurate and reproducible results.

Wearable sensors have received considerable attention since they enable continuous physiological monitoring toward maintaining an optimal health status and assessing physical performance. There are different types of wearable sensors such as watch, patch, etc. When they are used on skin, they are required flexibility and stretchability. In this study, we tried the lactate sensing in perspiration, which has widely been used for monitoring athletes’ performance, particularly in connection to intensive and endurance-based activities. For the development of wearable lactate sensor patch, we developed a stretchable biofuel cell (BFC) [1], of which output relates to concentration of fuel (lactate in this work). We used lactate oxidase (LOx) in oxidation of lactate with tetrathiafulvalene (TTF) as electron-transfer mediator and bilirubin oxidase (BOD) in reduction of O2, which were modified on stretchable textile modified with carbon nanotube. The stretchablity and sensitivity of the BFC-based lactate sensor were evaluated in details. The analysis of the real perspiration was also conducted with comparing with a commercial lactate sensor. We will present the results and will discuss the future of this type of biosensors.

References
[1] Y. Ogawa et al., Biosens. Bioelectron., 2015, 74, 947-952.

Acidity of the local microenvironments is an important parameter for detection of pathological conditions and understanding of cellular mechanisms. Silicon nanoribbon field effect transistor (FET) has been proved to be a high-throughput and sensitive platform for pH sensing. However, the efficiency of these sensors is limited by the biocompatibility of silicon material and its tendency for bio-fouling. Recent studies have demonstrated sub-2nm diameter carbon nanotube (CNT) porins embedded in lipid bilayers are fast and efficient proton conductors. In this research, we focus on a bioelectronic approach toward designing pH-sensing devices. We will describe an organic/inorganic hybrid device that combines nanoribbon FET with self-assembled CNT/lipid bilayer for pH sensing in physiological conditions. Finally, we will also discuss its potential application in nanometer spatial resolution intracellular biosensing.

Bisphenol A (4,4'-isopropylidenediphenol, BPA), formed by a condensation reaction between one acetone and two phenol molecules, is a major monomeric material for synthesizing polycarbonate plastics (CDs, automotive parts, baby water bottles, containers and lens of glasses) and epoxy resin (food cans, packing materials). While it has been broadly used for household and industrial purposes, a concern on the toxicity of BPA as one of the endocrine disruptors has restricted its use for practical applications. Since the BPA is easily leachable from household items, such as food packaging or plastic bottles, the public is highly vulnerable to BPA exposure and its toxicity. Widespread daily exposure to low levels of BPA and the potential adverse effects arising from its hormone-like behavior causing diverse health concerns including cancers, diabetes and heart diseases have posed increasing threats to public health. Therefore, there is an urgent need to develop detection methods for monitoring BPA concentration with high sensitivity and selectivity. In this work, a novel Bisphenol A sensor was developed harnessing an electrochemical platform comprising a layer-by-layer assembled reduced graphene oxide (rGO) electrode and a designer probe specifically recognizing BPA. The BPA detection probe, a recombinant protein (LacI-BPA), was constructed by fusing a disulfide-constrained high affinity BPA binding peptide (CKSLENSYC) to the C-terminus of Lac repressor (LacI). Following expression and purification, the LacI-BPA was heat-denatured on-purpose to facilitate its direct adhesion on the rGO electrode surface via pi-stacking interaction. When the performance of the fabricated BPA sensor (LacI-BPA/rGO) was assessed by electrochemical impedance spectroscopy (EIS), it showed a wide linear dynamic range of BPA detection spanning from 100 fM to 10 nM. Moreover, our BPA sensor exhibited negligible cross reactivity to BPA analogues such as Bisphenol S (BPS) and Bisphenol F (BPF) and almost complete spike recovery of BPA from plastic extracts containing various potential interferents. With these merits, the BPA sensor developed in the present study is expected to find practical application in selective and sensitive detection of BPA from diverse sample solutions.