Fabrication and reversible disulfide functionalization of PEGylated chitosan-based hydrogels: Platforms for selective immobilization and release of thiol-containing molecules

[Display omitted] •Chitosan-based with disulfide groups were employed in reversible thiol immobilization.•Benzothiazole disulfide exchange in functionalization of soft materials was realized.•Selective conjugation and cleavage of thiols demonstrated. In this study, we report on the fabrication of chitosan based hydrogel scaffolds incorporating reactive disulfide functionalities towards the reversible thiol immobilization and release endeavor. Native chitosan chemically modified with polyethylene glycol (PEG) groups was exploited in hydrogel synthesis together with an acryloyl group containing benzothiazole disulfide compound. The chemical crosslinking and incorporation of the reactive disulfide groups into the gel network was maintained by Michael addition of chitosan amino groups onto acrylic benzothiazole compound and bisacryloyl modified polyethylene glycol crosslinker. A series of hydrogels with different amounts of thiol reactive benzothiazole disulfide groups was obtained with moderately high gel conversions. The characterization of the hydrogels was performed by equilibrium swelling, structural morphology and rheology studies. The amount of reactive disulfide groups in the hydrogels were determined using UV–vis spectroscopy. Facile conjugation of a thiol-containing methyl red dye via thiol-disulfide exchange was demonstrated. The on demand cleavage of the attached thiol probe from the scaffold was achieved in the presence of a disulfide reducing agent, namely dithiothreitol (DTT). The efficient and simple fabrication of these hydrogels, as well as benign and reversible immobilization of thiol containing molecules onto the network could make these scaffolds as attractive platforms for biomedical applications such as bioconjugation/bioimmobilization, controlled drug/protein release and tissue engineering.