Electro-Biofabrication. Coupling Electrochemical and Biomolecular Methods to Create Functional Bio-Based Hydrogels

Abstract

Twenty years ago, this journal published a review entitled "Biofabrication with Chitosan" based on the observations that (i) chitosan could be electrodeposited using low voltage electrical inputs (typically less than 5 V) and (ii) the enzyme tyrosinase could be used to graft proteins (via accessible tyrosine residues) to chitosan. Here, we provide a progress report on the coupling of electronic inputs with advanced biological methods for the fabrication of biopolymer-based hydrogel films. In many cases, the initial observations of chitosan's electrodeposition have been extended and generalized: mechanisms have been established for the electrodeposition of various other biological polymers (proteins and polysaccharides), and electrodeposition has been shown to allow the precise control of the hydrogel's emergent microstructure. In addition, the use of biotechnological methods to confer function has been extended from tyrosinase conjugation to the use of protein engineering to create genetically fused assembly tags (short sequences of accessible amino acid residues) that facilitate the attachment of function-conferring proteins to electrodeposited films using alternative enzymes (e.g., transglutaminase), metal chelation, and electrochemically induced oxidative mechanisms. Over these 20 years, the contributions from numerous groups have also identified exciting opportunities. First, electrochemistry provides unique capabilities to impose chemical and electrical cues that can induce assembly while controlling the emergent microstructure. Second, it is clear that the detailed mechanisms of biopolymer self-assembly (i.e., chitosan gel formation) are far more complex than anticipated, and this provides a rich opportunity both for fundamental inquiry and for the creation of high performance and sustainable material systems. Third, the mild conditions used for electrodeposition allow cells to be co-deposited for the fabrication of living materials. Finally, the applications have been expanded from biosensing and lab-on-a-chip systems to bioelectronic and medical materials. We suggest that electro-biofabrication is poised to emerge as an enabling additive manufacturing method especially suited for life science applications and to bridge communication between our biological and technological worlds.

Redox-enabled Electronic Interrogation and Feedback Control of Hierarchical and Networked Biological Systems

“…Biofabrication 14 has allowed biological components to be assembled on micro-, or nano-scaled electronic devices for biosensing [15][16][17] or even control of biological functions 18 . Here, we enlisted electro-biofabrication 19 of biocompatible hydrogels to facilitate the assembly of enzymes and cells onto electrodes to localize signal transfer. For enzyme assembly, we show the spatially-configurable electrodeposition of a covalently-conjugated gelatin/horseradish peroxidase (HRP) 20 hydrogel film (Figure 2a, Supplementary Fig.…”

“…There was also no need to supplement with message-conveying redox mediators, since the signal was directly transferred from the electrode. Thus, we anticipate virtually any cell or consortia of cells can be assembled and electronically stimulated using this redox-based or other stimulusresponsive, electroassembly methodologies 19,24 .…”

Chitin/Chitosan Biocomposite Foams with Chitins from Different Organisms for Sound Absorption

“…Chitin, whether in its pure form or in solution, has seen limited utilization, highlighting an immediate necessity for application on a larger scale. While chitosan and related polysaccharides have been extensively used for biocomposite materials/hybrid materials, − including soft hydrogels, foams, and solid composite materials. , Lightweight insulation materials based on cellulose-chitosan for practical applications are also already known, stressing the importance of mechanical resistance and low density . Significantly less work has been reported about chitin. − In particular chitin-based foams were little explored. − For example, graphene oxide/chitin nanofibrils composite foams to dispose pollutants in aqueous solutions or chitin/chitosan-based nanofibril-reinforced starch foams possessed enhanced flammability and mechanical properties through chitin nanofibrils. , As Achinivu et al showed through the extraction of several different chitin biomass sources that processability, appearance, and mechanical properties highly depend on the chitin biomass source .…”