Biofabrication with biopolymers and enzymes: potential for constructing scaffolds from soft matter.

PURPOSE Regenerative medicine will benefit from technologies capable of fabricating soft matter to have appropriate architectures and that provide the necessary physical, chemical and biological cues to recruit cells and guide their development. The goal of this report is to review an emerging set of biofabrication techniques and suggest how these techniques could be applied for the fabrication of scaffolds for tissue engineering. METHODS Electrical potentials are applied to submerged electrodes to perform cathodic and anodic reactions that direct stimuli-responsive film-forming polysaccharides to assemble into hydrogel films. Standard methods are used to microfabricate electrode surfaces to allow the electrical signals to be applied with spatial and temporal control. The enzymes mushroom tyrosinase and microbial transglutaminase are used to catalyze macromolecular grafting and crosslinking of proteins. RESULTS Electrodeposition of the polysaccharides chitosan and alginate allow hydrogel films to be formed in response to localized electrical signals. Co-deposition of various components (e.g., proteins, vesicles and cells), and subsequent electrochemical processing allow the physical, chemical and biological activities of these films to be tailored. Enzymatic processing allows for the generation of stimuli-responsive protein conjugates that can also be directed to assemble in response to imposed electrical signals. Further, enzyme-catalyzed crosslinking of gelatin allows replica molding of soft matter to create hydrogel films with topological structure. CONCLUSIONS Biofabrication with biological materials and mechanisms provides new approaches for soft matter construction. These methods may enable the formation of tissue engineering scaffolds with appropriate architectures, assembled cells, and spatially organized physical, chemical and biological cues.