Nano-hydroxyapatite formation via co-precipitation with chitosan-g-poly(N-isopropylacrylamide) in coil and globule states for tissue engineering application

With the excellent biocompatibility and osteoconductivity, nano-hydroxyapatite (nHA) has shown significant prospect in the biomedical applications. Controlling the size, crystallinity and surface properties of nHA crystals is a critical challenge in the design of HA based biomaterials. With the graft copolymer of chitosan and poly(N-isopropylacrylamide) in coil and globule states as a template respectively, a novel composite from chitosan-g-poly(N-isopropylacrylamide) and nano-hydroxyapatite (CS-g-PNIPAM/nHA) was prepared via coprecipitation. Zeta potential analysis, thermogravimetric analysis and X-ray diffraction were used to identify the formation mechanism of the CS-g-PNIPAM/nHA composite and its morphology was observed by transmission electron microscopy. The results suggested that the physical aggregation states of the template polymer could induce or control the size, crystallinity and morphology of HA crystals in the CS-g-PNIPAM/nHA composite. The CS-g-PNIPAM/nHA composite was then introduced to chitosan-gelatin (CS-Gel) polyelectronic complex and the cytocompatibility of the resulting CSGel/composite hybrid film was evaluated. This hybrid film was proved to be favorable for the proliferation of MC 3T3-E1 cells. Therefore, the CS-g-PNIPAM/nHA composite is a potential biomaterial in bone tissue engineering. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.