Biotemplating of Functional Nanomaterials into Magnetically Driven Microrobots for Biomedical Applications

In micro and nanorobotics research, while a significant body of small-scale device investigation has been dedicated to building artificial versions of nature, other studies have exploited biological structures as templates or scaffolds to engineer robotic devices or machinery. This approach, known as Biotemplating, offers a robust methodology for manufacturing small-scale devices (i.e., micro and nanorobots) with potential applications in different fields like biomedicine.<br/><br/>Herein, we present a universal biotemplating approach that uses naturally occurring helical architectures to obtain controlled 3D assemblies of nanocrystalline of various functional materials like metal-organic frameworks (MOFs), piezoelectric nanoparticles, and 2D materials. Our process exploits Spirulina platensis, filamentous cyanobacteria with a helical body, which provides the shape of the final composite microstructure. Next, we create a magnetic helical chassis on top of the Spirulina platensis, which is subsequently coated with various functional nanocrystals. The resulting composite helical structure is a highly integrated, magnetically driven functional material-based microrobot.<br/><br/>In particular, taking advantage of these highly tunable materials, we demonstrated outstanding localizing drug delivery when biocompatible porous materials like Mil-100 nanoparticles are integrated with our magnetic biotemplates.<br/>Additionally, the inclusion of piezoelectric nanoparticles like Barium Tinante (BTO) allows us to fabricate magnetically driven microrobots with the capacity to degrade fibril proteins, such as Αβ-42 amyloid aggregates, involved in Alzheimer's disease. Our studies demonstrated that, under low-power ultrasound stimulation, the piezoelectric microbots generate reactive oxygen species (ROS) that can disintegrate the protein aggregates into smaller amyloids in less than one hour.<br/>Finally, the unique physicochemical properties of 2D-Materials like Molybdenum Difsufice (MoS2) grats the microrobots with the ability to locally increase the temperature. Our microrobots offer exceptional capabilities for photothermal ablation, inducing cancer cell killing with similar efficiency as state-of-the-art chemotherapeutic drugs.<br/>Moreover, the chemistry of the MoS2 can be easily modified in order to achieve additional functionalities. For example, we show that the microrobots can also serve as on-the-fly biorecognition platforms by decorating their surface with streptavidin-functionalized gold nanoparticles, which can selectively capture and transport biotin-coated microbeads.<br/><br/>In summary, we have created a universal biotemplating-based methodology to fabricate 3D helical assemblies with functional nanocrystals. Taking advantage of the specific chemistry associated with each kind of functional material, we are able to tune the microrobots to the application of interest. The countless possibilities of our newly introduced biotemplated methodology are only matched by the amount of different functional systems and their specific properties, opening the door to a vast number of application in micro and nanorobotics.