Polymeric micelle, the self-assembly of block copolymers with core-shell architecture, is a promising nanocarrier for drug and gene delivery. There are several relevant properties in polymeric micelle as nanocarrier systems, such as longevity in blood circulation, tissue-penetrating ability, spatial and temporal controlled drug release, and reduced inherent toxicity. Also, engineering of the block copolymer structure allows the preparation of polymeric micelles with integrated smart functions, such as targetability as well as stimuli-sensitivity. This presentation overviews the recent achievements as well as the future perspectives of polymeric micelles as smart nanocarriers for drug and nucleic acid delivery. Notable anti-tumor efficacy against hypovascular cancer, including pancreatic cancer and diffused-type stomach cancer, of the doxorubicin-incorporated polymeric micelles with pH-responding property will be demonstrated to emphasize a promising utility of the nanocarrier-modulated chemotherapy for the treatment of intractable cancers. Then, the focus of the talk will be placed to the application of gene-loaded polymeric micelles as non-viral vectors in the field of regenerative medicine, particularly bone regeneration. The result using micellar nanocarrier systems will be demonstrated for the successful generation of new bone in experimental animals by transducting genes encoding differentiation factors. Further, the future perspective of supramolecular nanodevices, including polymeric micelles, polymer vesicles, and photosensitive dendrimer assemblies, will be featured in the last part of this presentation, directing to the new medical paradigm of smart nanotheranostic systems controlled by external physical stimuli, particularly, photoillumination (nano-photomedicine).

Multifunctional polymeric nanoparticles have gained considerable interest in recent years for biomedical applications due to their potential to target and image diseased cells in vivo while also delivering therapeutics. Herein, we describe the synthesis and characterization of novel well defined core-shell nanoparticles which allow structure/property relationships for their biodistribution to be developed. The core-shell structure of the particles was characterized using small angle neutron scattering, cryogenic TEM, NMR and light scattering which confirmed a high degree of structural control over the size and functionality of these materials. By attaching radionuclides, the biodistribution of these nanoparticles with poly(ethylene oxide) coronas were studied by Cu⁶⁴ based positron emission tomography and shown to avoid the reticuloendothelial system. In order to add targeting capabilities to these nanoparticles, organic azides were incorporated at the periphery and Click chemistry was used to attach specific peptide sequences. This approach to functionalized nanoparticles has shown significant promise in specific receptor targeting under biologically relevant conditions, with both covalent attachment of functional groups as well as supramolecular assembly with therapeutic peptide amphiphiles. This allows a much greater understanding of the role of functional nanomaterials in biomedical applications to be developed.

Non-viral gene delivery has been widely investigated over the past decade as a means to guide tissue regeneration, treat disease and study gene function. However, low efficiencies of gene transfer and inability to target desired cell populations have limited the use of this approach. The present studies describe the design of a non-viral gene delivery vector that can utilize both the identity and the density of receptors at the cell surface to enhance non-viral gene transfer. Although current non-viral delivery approaches utilize receptors that are uniquely express at the cell surface for targeting, strategies that target the density of receptors at the cell surface have not been explored. We believe that by targeting multiple ligands at the cell surface simultaneously (multivalent binding), we can enhance targeting of the desired cell type and enhance gene transfer through the engagement of biological pathways that are unique to clustered receptors. Interestingly adenovirus 2 and 12 utilize this approach to enhance cellular internalization through proteins at their surface that contain spatially constrained integrin binding peptides that can interact with multiple integrin receptors simultaneously. In our present studies, we investigated the effect of spatially constrained Arg-Gly-Asp (RGD) peptides on the surface of DNA/polyethylene imine (PEI) polyplexes on the efficiency of non-viral gene transfer. RGD peptides were spatially constrained through immobilizing them to nanoparticles (nano-RGD). The resulting nano-RGD nanoparticles were used to decorate DNA/PEI polyplexes such that the polyplexes contain nanoparticles at their surface. One limitation of nanoparticles to display peptides is that many readily aggregate in salt containing solutions. To prevent aggregation we formed a monolayer protected gold cluster using peptides. The monolayer-protected clusters were stable in up to 500 mM salt compared to 40 mM for the unmodified nanoparticles. Through amino acid analysis it was found that there were approximately 1.3 peptides per nm2 immobilized to the nanoparticle. The ability of Au-RGD to enhance non-viral gene transfer of DNA/polyethylene imine polyplexes was studied in HeLa cells. It was observed that the presence of nano-RGD gold nanoparticles at the surface of DNA/PEI polyplexes resulted in enhanced luciferase gene expression. Our goal is to explore the use of a targeted non-viral gene delivery strategy that can engage multiple integrin receptors simultaneously to result in more effective non-viral gene delivery vectors.

Nature provides us with a great variety of interesting adhesive strategies that operate in wet and dry environments and that can serve to inspire the development of new materials. Marine and freshwater mussels, for example, have evolved sophisticated protein glues that serve to tether the mussel onto surfaces. After a brief description of the mussel adhesive proteins I will describe our efforts to develop biomimetic adhesives. Liquid surgical adhesives are being developed that incorporate catechols, one of the chemical constituents found in mussel adhesive proteins. The presence of the catechol in the polymer design lends both adhesive and cross-linking properties to the material. Temperature- and light-responsive systems will be described in which solidification of the adhesive is facilitated either by warming from ambient to body temperature or by application of light.

Cationic oligopeptides made from naturally-occurring amino acids have recently been widely explored as non-viral vectors for gene delivery1-4 due to their biodegradability, greater biocompatibility and ease of production as well as compositional control compared to polymer-based carriers. Existing designs for oligopeptides consist of either a combination of a) cationic arginine residues (for DNA binding) and a hydrophobic compound (e.g. stearyl or cholesterol to promote cellular uptake of oligopeptide/DNA complexes)1, or b) cationic lysine and pH-sensitive histidine moieties (for endolysosomal escaping)2. Here we, for the first time, design a class of short, cationic and amphiphilic peptides (A12H5K10-15, F5/I5/W5H4R8), and evaluate their ability to condense and deliver DNA into HEK293, HepG2 and 4T1 cell lines and a 4T1 mouse breast cancer model. The peptides were self-assemble into nanoparticles at high concentrations, which increased the local density of positive charge, leading to stronger DNA binding. Since the core of the nanoparticles was loosely packed, some hydrophobic amino acids might be distributed on the surface of peptide/DNA complexes after being complexed with DNA, promoting cellular uptake and membrane permeation. Therefore, greater gene transfection efficiencies were achieved. An increased length of lysine residues resulted in greater gene transfection efficiency. The hydrophobicity of the hydrophobic amino acid also affected gene transfection efficiency. Among I, F and W, the least hydrophobic W constantly induced the lowest gene transfection efficiency in all cell lines tested. The pH value, at which the DNA complexes were formed, was optimized for the peptides. At the optimized pH, A12H5K15 mediated high gene expression levels in HepG2 and 4T1 cells, comparable to those induced by the golden polyethylenimine (PEI) standard yet possessed much lower cytotoxicity. I5H4R8 achieved a peak luciferase expression level in 4T1 cells, which was 6.4 times higher than that mediated by PEI with nearly 90% of the cells viable. Intrinsically, the peptide was also less toxic than PEI with an IC50 value that was 5.0 times lower. More importantly, in a 4T1 mouse breast cancer model, the luciferase expression level achieved by I5H4R8 was about 13 times higher than that obtained with PEI. In summary, we have designed a new class of oligopeptides and evaluated their ability to deliver DNA both in vitro and in vivo. Our studies have proved that this new class of materials may be used as efficient vectors for delivery of DNA, siRNA, protein and other therapeutic macromolecules.References[1] S. Futaki et al., Bioconjugate Chem. 2001, 12, 1005-1011.[2] W. Yu et al., Nucleic Acids Res. 2004, 32, e48.[3] D. Trentin et al., Proc. Natl. Acad. Sci. 2006, 103, 2506-2511.[4] D. Luo, W. M. Saltzman, Nature Biotechnol. 2000, 18, 33–37.

Cellular state and function are orchestrated through spatio-temporally constrained molecular interactions. Understanding of these processes as they occur in real time is fundamental to biological research. Quantum dots (QDs) bioconjugates offers promises for biomedical application due to their unique optical properties. Despite the recent advances made in QDs-based bioimaging, the highly selective and non-permeable cell membrane has limited their widespread use in live cell imaging and diagnostics. Here we demonstrate an efficient and non-invasive intracellular delivery method of QDs using biodegradable and biocompatible nanocomposites for live cell microscopy. Incorporation of QDs into biocompatible PLGA nanoparticles resulted in enhanced cellular uptake through non-specific endocytosis. The exposure to low pH environment within endolysosomal compartments allows the escape of these nanoparticles into the cytoplasm, at where cargo release occurs through hydrolysis-induced degradation of the nanoparticle. Conjugation of nanocomposites with targeting moities enables the specific multiplexed labeling of cellular targets. In addition, QDs attached with molecular targeting agents can be delivered into the cytoplasm of live cells for real-time imaging and tracking of specific cellular components. Such system can be further modified into a universal delivery platform for targeted intracellular delivery of nanostructures.

Using transition metal catalysis chemistry for the polymerization of alpha-amino acid-N-carboxyanhydrides (NCAs), we have prepared amphiphilic diblock copolypeptides containing a variety of both hydrophilic and hydrophobic chains. The hydrophilic chains are composed of either cationic or anionic residues, and the hydrophobic chains are composed of natural non-polar amino acid residues such as leucine, valine and phenylalanine. By employing different amino acids, the chain conformations of individual domains can be altered. We report on the biomimetic self-assembly of block copolymers that form unilamellar vesicles or hydrogels with charged polypeptide coronas in aqueous solution. The vesicles are being explored for drug delivery applications, and the hydrogels are being explored for use in tissue regeneration in the central nervous system. We will describe how polypeptide design can be used to control interactions between the polypeptide assemblies and the cells and tissues relevant for these applications.

The long-term objective of our research is to develop new molecular componentry for the rapidly developing fields of micro- and nano-scale diagnostic devices. We have developed new approaches to molecular switching and molecular separations that utilize “smart” or stimuli-responsive conjugates and nanoparticles. Smart polymers serve as both antennae and actuators, to sense signals and respond to them, leading to control of biorecognition or molecular separation events in microfluidic channels. Their characteristic sharp responses in coil size and physical properties to small changes in pH, temperature, and/or electromagnetic irradiation over narrow ranges or at specific wavelengths permits rapid and precise control of molecular binding and adhesion events via “molecular switching” activities. The switching properties of the polymer chains can be coupled to the switching of enzyme activity when the polymer is end-grafted near the enzyme active site. When the polymer-enzyme conjugates are put in solution, kinetic characterization and conjugation site analysis indicate that the enzyme is brought into the aggregated state by the collapsed polymer in an orientation that blocks substrate access. When the polymer is attached away from the binding site, the enzyme active sites must be oriented away from the polymer-rich phase to largely preserve activity. Protein-polymer aggregates display the properties of nanogels with well-defined sizes that can be controlled by concentration and polymer chain length. Once formed, the nanogels are remarkably stable with narrow size distributions, and yet can be formed or dissolved rapidly. The protein-polymer conjugates have also been developed for upstream processing of diagnostic targets in microfluidic devices. We initially developed an affinity purification matrix that was designed to be injectable and that could be set up reversibly at defined positions in microfluidic channels. This matrix consists of stimuli-responsive bioanalytical beads that can be reversibly immobilized on microfluidic channel walls to capture and release diagnostic targets. This temperature-responsive affinity chromatography matrix can thus be injected into a microfluidic channel device and aggregated at the positions where heaters signal a temperature change, followed by the controlled release of affinity-captured targets back into the microfluidic flow-stream as the heater is turned off. This smart nanobead system was extended to develop an injectable immunoassay system in a channel zone that can be simply controlled by integrated heating elements. It provides a simple approach to multiplexing through the simultaneous or sequential injection of different antibody-coated bead species, potentially at multiple sites in the integrated device channels.We have recently extended this system to include a channel surface trap composed of graftedstimuli-responsive polymer chains PNIPAAm was grafted onto polydimethylsiloxane (PDMS) surfaces by a UV-mediated graft polymerization from a photoinitiator that was preadsorbed in the channel wall. The surface traps capture PNIPAAm-grafted nanobeads uniformly above the LCST and facilitate their rapid release as the temperature is reversed to below the LCST. This dual surface trap and injectible chromatography system could be useful in many applications, such as affinity separations, immunoassays, and enzyme bioprocesses by providing for the controlled capture and release of chromatography beads.

This paper reports the development and characterization of MetaSense, a non-intrusive metabolic microsensor for clinical organ transplantation. MetaSense would replace periodic laboratory diagnosis tests with a continuous monitor that provides real-time data on organ viability from the moment of harvest, through support and finally to the end of the transplant surgery.MetaSense design allows it to be placed on top of the organ’s external layer. Micro-heaters at the bottom layer of MetaSense provide a burst of thermal energy to ablate holes in the organ’s epidermis and reach non-invasively the interstitial fluids to be sampled. Twenty five independent sensing cells act as a 2-microelectrode electrochemical detection system, having one of the microelectrodes modified with conductive polymer polypyrrole (PPy) and corresponding enzyme. Choice of strong and biocompatible polymer materials was critical since the microsensor must function over 20°C to 40°C temperature range and should operate in different surroundings such as blood, interstitial fluid and buffered solutions. The fabrication process consists of five steps and uses polymer SU8 as a principal structural material. Cross-linked SU8 is very difficult to release from the substrate, therefore a novel wet release technique using polymethylglutarimide resist OmniCoat™ as a release layer was developed. The first step in the fabrication was the deposition of ~25nm OmniCoat™ layer on silicon substrates followed by a thick (150µm) SU8 layer. Furthermore, 200Å of Chromium and 1300Å of Gold were sputtered coated on top of the SU8 layer. Metal electrodes and micro-heaters were patterned using photolithography. OmniCoat™ release layer was then dissolved in Tetramethylamonium hydroxide. Polymethylmethacrylate (PMMA) insulating interface layer was deposited and selectively etched on top of the metallization layer. Lastly PPy along with enzyme and redox mediator was selectively deposited on one of the microelectrodes.Glucose and lactate are the specific, biologically relevant molecules along with enzymes glucose oxidase (GOx) and lactate dehydrogenase (LDH) that were chosen to assess organ viability. The concentration of glucose correlates with metabolic rate, indicating how well the metabolism has been resuscitated following ischemia. The amount of lactate would estimate the compensatory anaerobic metabolism. Chrono-amperometric technique was used to study the in-vitro characteristics of MetaSense. Plots of increasing current due to the increase in glucose concentration measured during in-vitro analysis were registered. By quantifying GOx two Flavin Adenine Dinucleotide cofactors, the concentration of GOx encapsulated in the polymer matrix was determined to be 0.15µM/cm2, which would help understand about the sensitivity of the device. Future work will include detailed ex-vivo experiments with the MetaSense device on bovine kidney samples.

A novel approach to sensitive, rapid, and multiplexed antigen detection is described. In the presence of a specific antigen, quantum dot-antibody conjugates rapidly self-assemble into agglomerates that are typically more than one order of magnitude larger than their individual components. The size distribution of the agglomerated colloids depends on, among other things, the relative concentration of quantum dot conjugates and antigen molecules. Quantum dot agglomerates mediated by antigen recognition were characterized by measuring their light scattering and fluorescence characteristics in an unmodified flow cytometer. This simple technique enables the potential simultaneous detection of multiple antigenic biomarkers directly from physiological media and could be used for early detection and frequent screening of cancers and other diseases.