Layered hydrogel of poly(γ-glutamic acid), sodium alginate, and chitosan: Fluorescence observation of structure and cytocompatibility

In this study, a novel layered hydrogel composing of poly(γ-glutamic acid) (PGA), chitosan (CS), and alginate (AL) were prepared. Furthermore, PGA, CS, and AL were labeled with different fluorescent dyes. The bilayer structure of hydrogel was then revealed using these fluorescent labeled polymers. To mimic the stability of these hydrogels in physiological fluids, the dissolution of PGA and the release of Ca2+ from these hydrogels in normal saline were also monitored. The results showed that by adding CS to the hydrogel, the dissolution of PGA was decreased by 67%, and the release of Ca2+ was reduced by 40%. In addition, the hydrogel exhibited no cytotoxicity for L929 fibroblasts.

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► Layered hydrogel composed of poly(γ-glutamic acid), chitosan, and alginate.
► Layered structure revealed by fluorescent-labeling constituents under fluorescence microscope.
► The presence of chitosan improved the stability of hydrogel in physiological environment.
► These layered hydrogels exhibited no cytotoxicity.