Preparation And Property Analysis Of Chitosan-g-poly(N-isopropylacrylamide)/nano-hydroxyapatite Composite

With excellent biocompatibility and osteoconductivity, nano-hydroxyapatite(nHA) has shown significant prospect in the biomedical applications. Controlling thesize, crystallinity and surface properties of nHA crystals are the critical challenge inthe design of HA based biomaterials.In this article, with the graft copolymer of chitosan and poly(N-isopropylacrylamide) in coil and globule state as the template respectively, novelcomposites of Chitosan-g-Poly (N-isopropylacrylamide)/nano-hydroxyapatite(CS-g-PNIPAM/nHA) were prepared via co-precipitation, and used as a templating inthe synthesis of nHA crystals in situ. Because of the CS-g-PNIPAM copolymerexisting at different aggregation states which contain isolated molecular coil andglobule at different temperature, the environments for nHA crystals formation aredistinguishing and then the mechanisms are different. The difference essentiallyoriginates from the location where PNIPAM side chain or HA stays in.In the following research，we use Zeta potential analysis, Thermogravimetricanalysis (TGA) and X-ray diffraction (XRD) to identify the formation mechanism ofthe CS-g-PNIPAM/nHA composites and the morphology was observed bytransmission electron microscopy (TEM). Results suggested that the physicalaggregation states of the template polymer could induce or control the size,crystallinity and morphology of HA crystal in CS-g-PNIPAM/nHA composites.Furthermore, the excellent biocompatibility of CS-g-PNIPAM/nHA compositesimproves biological responses of pre-osteoblast (MC3T3-E1) to CS-Gel/compositehybrid films including cell proliferation and morphology in comparison with CS-Geland CS-Gel/nHA films. Thus, it is expected that CS-g-PNIPAM/nHA composites witha desirable physico-chemical and biological properties are expected to meet theessential requirements for bone tissue engineering.