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-hydroxysuccinimide (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 thermosensitive 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.