Modification And Functionlization Of Hydroxyapatite Surface And Its Applications

More and more researchers focus on the high performance of biomaterials in these years.The surface modification is considered to be an effective way to meet the new demand of bone repair in orthopaedics,besides design and preparation of new biomaterials with good comprehensive properties.In this paper,surface modification on hydroxyapatite(HA) was investigated systematically in order to improve the bonding of HA with polymer matrix and to increase the cytocompatibility of HA.The biocompatibility of the resulting materials was eValuated.In this work,the main following research results have been obtained.1) Since the mechanical performances of inorganic/polymer composites were greatly decided by interfacial boding strength of two phases,octadecyltrichlorosilane (OTS) was used as a coupling agent to modify the surface of HA by a silanization reaction for creating a surface capable of chemical bonding with polymers.The maximum quanlity of OTS modified layer on HA surface was upto 2.9at%Si.2) Using the OTS modified HA powders,porous PLLA/HA composites were prepared.Compared with the composite with unmodified HA,elastic modulus of PLLA/OTS modified HA composite increased 2 times from 2.14MPa to 6.44 MPa; compressive strength increased 1 times from 0.556 MPa to 0.949 MPa.In vitro BMSCs(Bone Mesenchymal Stem Cells) cultivation results showed that BMSCs could adhere and grow normally on PLLA/OTS modified HA composite support,and had good living situation and proliferation.Hnece,PLLA/OTS modified HA composites are a bone substitute material with good cytocompatibility.3)γ-aminopropyltriethoxysilane(γ-APTES) was used to modify HA as a coupling agent,then RGD was immobilized on the modified surface of HA.Zeta potential and XPS analysis results showed APTES was combined with HA by chemical bonding, and element analysis results showed that RGD were successfully immobilized on HA.4) Porous PLLA/RGD immobilized HA composites were prepared.In vitro BMSCs cultivation results showed that BMSCs adhesion ratio of PLLA/RGD immobilized HA cpmosite increased from 37.21%to 69.11%greatly,nearly 2 times of PLLA/HA composite.Hence,RGD in the porous composite functioned well as adhering cells.5) HA coatings were firstly modified by APTES and immobilized by RGD later. The results showed that RGD was combined on the surface of APTES modified HA coating through a covalent bond.Thus,RGD can exist on HA coating surface very stably.Although RGD could appear on HA coating by physical absorption,its existing situation of RGD was rather unstable,all RGD molecules on HA coating by physical absorption were removed away by ultrasonic treatment.6) In vitro BMSCs cultivation showed:the biological performance of RGD immobilized HA coating was greatly improved,BMSCs adhesive ratio increased nearly 2 times from 22.1%to 59.3%,the RGD on the HA coating could play a significant role in enhancing more BMSCs adherence.MTT results showed the proliferation on the RGD immobilized HA coating was much better than that on HA coating..In addition,morphologic analysis results showed that more BMSCs adhered on the RGD immobilized HA coating,they had good cells shape with strong living situation.