Study On The Preparation And Properties Of PDLLA/PRGD/n-HAP Porous Composite

With the development of nerve regeneration and tissue engineering,the demand for biological materials has transmited the materials from good biocompatibility and biodegradability to good bioactivity.A new generation of bioactive materials can promote cell proliferation,differentiation and adhesion of growth.Traditional polylactic acid（PDLLA）materials because of its non-toxic,good biocompatibility and biodegradability has been applied in the field of human clinical tissue engineering by the FDA organization.But the traditional PDLLA materials has its fatal disadvantages:（1）lack of surface hydrophilic group,which leads to the strong hydrophobic surface and poor cell adhesion;（2）lack of surface functional groups,limit the introduction of other functional groups;（3）material degradation leading to the accumulation of acidic,causing tissue inflammation.In order to overcome the above disadvantages,and toward the biological activity development,many scholars have a lot of research on modification of PDLLA.Maleic anhydride（MAH）having an high active anhydride,it is easy to open loop formation of carboxyl;Arg-Gly-Asp（RGD）polypeptide is an amino acid sequence,it is can promote the growth of cell adhesion;Hexamethylene diamine and hydroxyapatite（HAP）can enhance the hydrophilicity of the PDLLA and degradation product is alkaline can neutralize some of the acid produced by degradation of PDLLA.In this paper,PDLLA as raw material,through the introduction of MAH,hexamethylene diamine,GRGDY polypeptide and hydroxyapatite form a porous composite material,and a series of material characterization and analysis.In this paper,a high molecular weight PDLLA as raw material,oxidation dibenzoyl peroxide（BPO）as initiator,under the high temperature the MAH with PDLLA reaction by free radical polymerization method,and preparation anhydride modified poly lactic acid material（MPLA）.Then under the conditions of low temperature water bath,the anhydride ring opening to form carboxyl groups,introducing hexanediamine preparation hexamethylene diamine modified poly lactic acid material（HMPLA）.Finally,1-ethyl-3-（3-（dimethylamino）propyl）carbon diimine hydrochloride（EDC）and 1-hydroxy benzene benzotriazole（HOBt）as condensing agent,the introduction of polypeptide GRGDY synthetic polymeric materials PRGD.In order to improve the performance of the polymer,the polymer material with the silane coupling agent（KH-560）modified nano-hydroxyapatite（n-HAP）composite and preparation of porous composite material.The infrared（FTIR）,nuclear magnetic resonance(¹³C NMR,¹H NMR),differential scanning calorimetry（DSC）were used to characterize the material,showed that maleic anhydride（MAH）and hexamethylenediamine has successfully introduced side chain of PDLLA.Molecular weight and molecular weight distribution of the material was tested by GPC,indicates that with the increase of the amount of MAH and hexamethylenediamine,the smaller molecular weight material.Measured the content of amino acid in 16.5⁴8.8 mol/g by the amino acid analyze（AAA）.PDLLA/n-HAP composite material interface and porous morphology were investigated by SEM,and investigate the effect of n-HAP addition on the biological properties of materials by the degradation experiment in vitro.The experimental results show that the hydrophilicity of PDLLA/PRGD/n-HAP composite material can be improved.In vitro degradation experiments,pH,weight loss,surface morphology of the material were investigated,the pH of pure PDLLA material is gradually reduced.When degraded to 12 weeks,the pH value is 6.4,composite materials that were added hexamethylenediamine are staying at around 6.8,but composite materials that were added n-HAP and hexamethylenediamine are staying at around 6.95.The weight loss rate of the materials is quickly at first and then became slower,At the same point in time,the quality pure PDLLA loss minimum,PDLLA/PRGD/n-HAP quality loss followed and the PDLLA/PRGD quality loss is the largest.The molecular chain structure of polymer composite was destroyed due to the introduction of hexamethylenediamine and GRGDY,and molecular weight reduction.PRGD of small molecular weight dissolved more easily lead to decrease of pH value,resulting in increased material mass loss.Cytotoxicity test show that the modified polymer composite material is more promote cell growth and adhesion than pure PDLLA.