Poly(ethylene glycol)-interpenetrated genipin-crosslinked chitosan hydrogels: Structure, pH responsiveness, gelation kinetics, and rheology

In the development of pH-responsive chitosan-based hydrogels, achieving reproducible porosity and swelling behavior is essential for the design of hydrogel networks. Herein, we enhance the level of control in hydrogel microarchitecture by incorporating poly(ethylene glycol) (PEG) into the chitosan-genipin matrix. Hydrogels, varied in composition, were synthesized under mild conditions (37 degrees C, 1 atm, 24 hr), yielding microporous structures with a pore diameter ranging from 11 to 57 mu m and an average cross-sectional porosity of approximately 40-64%. Compared to chitosan-genipin hydrogels without PEG, presence of PEG in concentrations up to 1.9 mM generated the same effect as would increase in genipin content, yielding structures with a smaller pore diameter, a lower swelling degree in pH 2 buffer and a higher elastic modulus. Considering cost effectiveness and scale-up, reducing genipin content by the addition of PEG is favorable. Importantly, hydrogel samples containing higher concentrations of PEG (2.9 mM and above) showed a sudden increase in the swelling degree accompanied with a decrease in the elastic modulus. Findings showcase the potential variation in the composition of these hydrogels has in yielding scaffolds with significantly different physico-chemical behaviors.