Bridging the Bio-Electronic Interface with Biofabrication

Abstract

Advancements in lab-on-a-chip technology promise to revolutionize both research and medicine through lower costs, better sensitivity, portability, and higher throughput. The incorporation of biological components onto biological microelectromechanical systems (bioMEMS) has shown great potential for achieving these goals. Microfabricated electronic chips allow for micrometer-scale features as well as an electrical connection for sensing and actuation. Functional biological components give the system the capacity for specific detection of analytes, enzymatic functions, and whole-cell capabilities. Standard microfabrication processes and bio-analytical techniques have been successfully utilized for decades in the computer and biological industries, respectively. Their combination and interfacing in a lab-on-a-chip environment, however, brings forth new challenges. There is a call for techniques that can build an interface between the electrode and biological component that is mild and is easy to fabricate and pattern.Biofabrication, described here, is one such approach that has shown great promise for its easy-to-assemble incorporation of biological components with versatility in the on-chip functions that are enabled. Biofabrication uses biological materials and biological mechanisms (selfassembly, enzymatic assembly) for bottom-up hierarchical assembly. While our labs have demonstrated these concepts in many formats 1,2,3 , here we demonstrate the assembly process based on electrodeposition followed by multiple applications of signal-based interactions. The assembly process consists of the electrodeposition of biocompatible stimuli-responsive polymer films on electrodes and their subsequent functionalization with biological components such as DNA, enzymes, or live cells 4,5 . Electrodeposition takes advantage of the pH gradient created at the surface of a biased electrode from the electrolysis of water 6,7 ,. Chitosan and alginate are stimuli-responsive biological polymers that can be triggered to self-assemble into hydrogel films in response to imposed electrical signals 8 . The thickness of these hydrogels is determined by the extent to which the pH gradient extends from the electrode. This can be modified using varying current densities and deposition times 6,7 . This protocol will describe how chitosan films are deposited and functionalized by covalently attaching biological components to the abundant primary amine groups present on the film through either enzymatic or electrochemical methods 9,10 . Alginate films and their entrapment of live cells will also be addressed 11 . Finally, the utility of biofabrication is demonstrated through examples of signal-based interaction, including chemical-to-electrical, cell-to-cell, and also enzyme-to-cell signal transmission.Both the electrodeposition and functionalization can be performed under near-physiological conditions without the need for reagents and thus spare labile biological components from harsh conditions. Additionally, both chitosan and alginate ...

Cellulose Nanocrystals—Bioactive Glass Hybrid Coating as Bone Substitutes by Electrophoretic Co-deposition: In Situ Control of Mineralization of Bioactive Glass and Enhancement of Osteoblastic Performance

“…10 Moreover, functional groups such as amino, carboxyl, and hydroxyl groups introduced by polymer molecules could be preserved at room-temperature to facilitate the entrapment of biological entities for the biofunctionalization of metallic implants. 11,12 In addition, the presence of the polymer component leads to a "soft" coating, which, in comparison to hard coatings composed of pure ceramics, can be expected to promote improved mechanical contact between the rigid metal implant and the compliant bone tissue.…”

“…Addition of a polymer phase will not only strengthen the porous inorganic coating structure and the bonding to the surface of the implant, but it also plays a role in retarding the ion release rate from BG particles embedded in the polymer matrix . Moreover, functional groups such as amino, carboxyl, and hydroxyl groups introduced by polymer molecules could be preserved at room-temperature to facilitate the entrapment of biological entities for the biofunctionalization of metallic implants. , In addition, the presence of the polymer component leads to a “soft” coating, which, in comparison to hard coatings composed of pure ceramics, can be expected to promote improved mechanical contact between the rigid metal implant and the compliant bone tissue.…”