Preparation And Characterization Of Chitosan-polymethyl Acrylic Acid/hydroxyapatite Composite Materials

As single biomaterial is very different to satisfy the requirements of bone tissue engineering scaffold materials,such as biocompatibility,biodegradability,easy shaped,good bone inductivity and good mechanical properties,composite materials between different materials can concentrate the advantages of each materials,and composite materials with biocompatibility,biodegradability and good mechanical properties can be prepared.Chitosan/hydroxyapatite(CS/HAP)composite materials can over come the shortcomings of lack of induced osteogenesis and big brittleness,combine the hardness of HAP with toughness of CS,combine the porousness of HAP with biodegradablity of CS,combine the induced osteogenesis of HAP with bioactivity of CS.In that case,we can develop composite materials with the characterisitics of good biocompatibility,biodegradability and induced osteogenesis,meanwhile,with improving mechanical properties to satisfy the requirements of bone framework.However,there are big differences between the surface properties of inorganic HAP and organic CS,and thus influence the homogeneity and mechanical properties of the composite materials due to the weak interface interaction.As a result,the introduction of-COOH into the chains of CS can improve the homogeneity and stability of composite materials because of the introduction of grouth point of-COOH,it makes the HAP crystals couple with basis material tightly,and improve the mechanical properties effectivly.The aim of this work is to prepare composite materials with the advantages of biocompatibility,biodegradability,induced osteogenesis and improved mechanical properties.Firstly,chitosan-polymethylacrylic acid(CS-PMAA)polyelectrolyte nanoparticles were prepared with the materials CS and MAA,chemical structure and crystal form were characterized by FTIR and XRD,the actual composition of the nanoparticles were determined by aoto-titration,the swell properties of CS-PMAA and stability were measured by UV-vis,the variation of particles size with pH and morphology were studied by DLS and TEM.Results suggest that CS-PMAA polyelectrolyte nanoparticles were successfully synthesized by the electrostatic interaction between-NH3+ and-COO-,the variation of particles size with pH shows "M" shape,it means at a pH of 5,the particles size is minimum,and at pH of 3 and 9,the size increase.Under the conditions of strong acid and strong alkali,the hydrolysis of amino of chitosan are accelerated,it make CS chain out of polyelectrolyte nanoparticles,and thus particle size decreases.The actual composition of the nanoparticles,determined by aoto-titration,were smaller than raw materials,which provides theoretical guidance for the preparation of HAP.CS-PMAA/HAP composite materials were prepared by chemical precipitation method on the CS-PMAA substrate.FTIR shows the absorption peak of HAP are existed in the composites,and the red shift of absorption peak are observed due to ion electrostatic interaction.HAP crystal were successfully synthesized by the XRD analysis.The actual contents of each component equals to the theory contents analyzed by TGA data.The morphology of the HAP crystals were observed by SEM and TEM,results suggest that HAP crystals are successfully synthesized the CS-PMAA substrate,the HAP crystals are tightly bound to the CS-PMAA substrate without separation,due to the strong electrostatic interaction between carboxyl group and calcium ion,it suggest,to a certain extent,that this interaction can improve the mechanical properties of composite materials.The composite materials have a nice prospect in the field of bone tissue engineering.