Synthesis and characterization of thermosensitive chitosan copolymer as a novel biomaterial

Novel water-soluble thermosensitive chitosan copolymers were prepared by graft polymerization of N-isopropylacrylamide (NIPAAm) onto chitosan using cerium ammonium nitrate (CAN) as an initiator. The physicochemical properties of the resulting chitosan-g-NIPAAm copolymers were characterized by Fourier transform infrared (FT-IR) spectroscopy, 1H-nuclear magnetic resonance, X-ray diffraction measurement, thermogravimetric analysis (TGA) and solubility test. Sol-gel transition behavior was investigated by the cloud point measurement of the chitosan-g-NIPAAm aqueous solution. The gelling temperature was examined using the vial inversion method. The percentage of grafting (%) and efficiency of grafting (%) were investigated according to concentrations of monomer and initiator. The maximum grafted chitosan copolymer was obtained with 0.4 M NIPAAm and 6 x 10(-3) M CAN. Water-soluble chitosan-g-NIPAAm copolymers were prepared successfully and they formed thermally reversible hydrogel, which exhibits a lower critical solution temperature (LCST) around 32 degrees C in aqueous solutions. A preliminary in vitro cell study showed nontoxic and biocompatible properties. These results suggest that chitosan-g-NIPAAm copolymer could be very useful in biomedical and pharmaceutical applications as an injectable material for cell and drug delivery.