Electrochemically driven assembly of chitosan hydrogels on PEDOT surfaces

Hydrogels are attracting interest in the field of bioelectronics due to their ability to serve as coatings on electrodes, improving the electrochemical interface, addressing the mechanical mismatch, and offering potential for localized drug or cell delivery. Challenges persist in integrating hydrogels with electrodes typically composed of metals and/or organic semiconductors. Here, an electrochemically driven method is introduced for direct growth of chitosan hydrogels onto poly(3,4-ethylenedioxythiophene) (PEDOT) surfaces. The growth of ionic gelation chitosan is triggered by electrical release of a specific dopant, tripolyphosphate (TPP), from PEDOT. As a result, chitosan hydrogels grow directly from the PEDOT surface and firmly attach to it. Although this process temporarily reduces PEDOT to the benzoid structure, its unique electroactivity allows for reversible conversion to the quinoid structure after chitosan hydrogel assembly. Once assembled, the chitosan hydrogel coating can be further functionalized. The introduction of covalent cross-links and incorporation of additional interpenetrating polymer networks (IPNs) are explored. Electrochemical characterization reveals that an interface with favorable properties is formed between PEDOT and ionic-covalent chitosan, functionalized with a PEDOT IPN. The electroactivity of the proposed method surpasses any other PEDOT/chitosan system reported in the literature. These results underscore the potential of this material for bioelectronics applications.