Thermosensitive Chitosans as Novel Injectable Biomaterials

Two kinds of water soluble thermosensitive chitosan copolymers were prepared by graft polymerization of N-isopropylacrylamide (NIPAAm) onto chitosan using cerium ammonium nitrate (CAN) as an initiator (chitosan-g-NIPAAm) and by coupling monocarboxy Pluronic^® with chitosan using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccin-imide (NHS) as coupling agents (chitosan-Pluronic^®). The physicochemical properties of the resulting copolymers were characterized and they formed thermally reversible hydrogel, which exhibits a lower critical solution temperature (LCST) at 34°C in aqueous solutions. The human mesenchymal stem cells (hMSCs) were cultured in the chiotsan-g-NIPAAm in vitro. Chondrogenic differentiation was induced in the chitosan-g-NIPAAm gel. Therefore, chondrogenic differentiated cells from MSCs with a thermo-sensitive chitosan-g-NIPAAm could be used as an injectable cell-polymer complex. In summary, chitosan-g-NIPAAm and chitosan-Pluronic^® attest to their usefulness as injectable materials because of their thermally reversible property and relatively good biocompatibility.