Electrodeposition of reduced graphene oxide with chitosan based on the coordination deposition method

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

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.

Improving Corrosion Protection and Friction Resistance of Q235 Steel by Combining Noncovalent Action and Rotating Coating Method

Developing waterborne epoxy (WEP) coatings with excellent corrosion resistance and tribological properties is a key aspect to solve the damage of Q235 steel. In this work, perylene bisimide (PBI) derivatives dispersion graphene (GR) were prepared by a π-π stacking, the highly orientated PBI0.5%/GR0.5%/WEP coating will be prepared by the rotating coating method. Especially, the impedance value reached about 109 Ω·cm2 when the PBI and GR ratio is 1:1. The impedance value of PBI0.5%/GR0.5%/WEP coating increased by 3 orders of magnitude compared with that of pure WEP coating (106 Ω·cm2). Additionally, the coefficient of friction of the coatings was 0.33; compared with that of WEP, the coefficient of friction decreased by 48%, and the wear resistance increased by 87.6%. The results show that the PBI0.5%/GR0.5%/WEP coatings exhibited excellent corrosion resistance and wear resistance properties due to the good dispersion and high orientation of PBI/GR in WEP. It is anticipated that our current work would guide the ongoing efforts to develop a more efficient method to overcome the poor dispersion of GR in waterborne epoxy resin and provide a green coating with excellent corrosion resistance and wear resistance properties.