Thermosensitive Chitosans as Novel Injectable Biomaterials

Abstract

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.