A zwitterionic serine modified chitosan derivative for improving protein stability and activity.

A zwitterionic phosphoryldiserine (PDS)- chitosan conjugate was synthesized via Atherton-Todd reaction, and its degree of substitution of PDS and structure were characterized by H and P NMR spectra, ICP, FTIR and XRD. Thermal analysis confirmed that there existed the freezing bound water surrounding PDS-chitosan due to the introduction of zwitterionic PDS groups onto chitosan backbone. In vitro cytotoxicity and hemolysis assay demonstrated that PDS-chitosan had excellent cell compatibility.