Photoinduced chitosan-PEG hydrogels with long-term antibacterial properties

Photochemical processes offer the possibility to prepare functional hydrogels in green conditions that are compatible with both synthetic and natural polymers. Here hydrogels associating chitosan derivatives and poly(ethylene glycol) (PEG) have been successfully synthesized under light illumination in aqueous conditions. Kinetic studies under irradiation showed that less than 2 min were necessary to obtain fully cross-linked networks. Thermomechanical analyses and swelling experiments indicated that introduction of chitosan overall weakens the hydrogel network but can create domains of higher thermal stability than the PEG-alone structure. The resulting chitosan-PEG hydrogels demonstrated a tremendous inhibition (100%) of the bacterial growth (Escherichia coli and Staphylococcus aureus). After 6 months ageing, one of the hydrogel preserved a high antifouling activity against Escherichia coli. This interesting result, that could be correlated with the network features, demonstrates the strong potentiality of these photochemical methods to obtain robust bio-functional materials.