Polyphenol-functionalized hydrogels using an interpenetrating chitosan network and investigation of their antioxidant activity

In this work, polyphenol-modified hydrogels were prepared and their antioxidant activities were investigated. Poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogels were first synthesized and subsequently functionalized with an interpenetrating polymer network (IPN) structure comprising crosslinked chitosans and p(HEMA) networks. The resulting hydrogels were further modified with polyphenols such as gallic acid and dopamine through amide coupling reactions to afford the antioxidant hydrogels. The antioxidant activity of the prepared hydrogels were evaluated using 2,2-diphenyl-1-picrylhydrazyl and 2,2’-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) radical scavenging assays. The gallic-acid-modified hydrogels exhibited superior antioxidant activity when compared to their dopamine-functionalized counterparts; this was correlated to the number of hydroxyl groups in the benzene ring. Moreover, longer chitosan moieties afforded larger amounts of polyphenols. Thus, hydrogels containing the same polyphenols but longer chitosan moieties exhibited stronger antioxidant activity. This work demonstrates that the development of antioxidant hydrogels based on chitosan-IPN structures shows great potential for application in biomedical devices and ophthalmic materials.