Antibacterial activity and biocompatibility of a chitosan–γ-poly(glutamic acid) polyelectrolyte complex hydrogel

In this study, we prepared a polyelectrolyte complex (PEC) hydrogel comprising chitosan as the cationic polyelectrolyte and γ-poly(glutamic acid) (γ-PGA) as the anionic polyelectrolyte. Fourier transform infrared spectroscopy revealed that ionic complex interactions existed in the chitosan–γ-PGA PEC hydrogels. The compressive modulus increased upon increasing the degree of complex formation in the chitosan–γ-PGA PEC hydrogel; the water uptake decreased upon increasing the degree of complex formation. At the same degree of complex formation, the compressive modulus was larger for the chitosan-dominated PEC hydrogels; the water uptake was larger for the γ-PGA-dominated ones. Scanning electron microscopy images revealed the existence of interconnected porous structures (pore size: 30–100 μm) in all of the chitosan–γ-PGA PEC hydrogels. The chitosan–γ-PGA PEC hydrogels also exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, in vitro cell culturing of 3T3 fibroblasts revealed that all the chitosan–γ-PGA PEC hydrogels were effective in promoting cell proliferation, especially the positively charged ones (chitosan-dominated). Therefore, the chitosan–γ-PGA polyelectrolyte hydrogel appears to have potential as a new material for biomedical applications.

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