Surface Functional Modification Of Biomedical Carbon/Carbon Composites

With the development of modern medical technology and transportation tools,the acceleration of population aging,and the increasingly frequent traffic accidents,the demand for bone replacement materials is increasing.Carbon/carbon composites?C/C?inherit the inherent biocompatibility of carbon materials,overcome the fragility of a single carbon material,and have excellent biomechanical performance.The microporous structure on the surface of C/C is beneficial to the ingrowth of tissues,and it is considered to be a potential bone repair and bone tissue replacement material.As known to all,bio-inertia for medical C/C lead to bone integration defects and bacterial infection.To improve C/C biological activity and antibacterial property,speed up bone tissue reconstruction,shorten the healing time,the hydroxyapatite?HA?modified layer,chitosan?CS?modified layer,CS/HA composite modified layer were constructed on the C/C surface by means of biomimetic mineralization technology,electrochemical accelerated mineralization method,self-assembly technology and covalent grafting.The surface morphology,phase structure,chemical composition,functional group and wettability of the coating were characterized by SEM,EDS,XRD,FTIR,XPS and contact angle test.The in vitro cell culture and bacteriostasis test were used to explore the coating's bone repair ability and bacteriostasis.The active calcium phosphate modified coating was constructed on the surface of C/C composites by electrochemical accelerated mineralization.The effects of various electrochemical mineralization factors?mineralization time,mineralization current,electrolyte temperature and electrolyte concentration?on the morphology of mineralized coatings were studied.The results show that under the conditions of mineralization voltage of-1.8 V,mineralization current of 0.03 A,electrolyte temperature of 37?,electrolyte concentration of1.5 times and mineralization time of 10 min,a homogeneous biomimetic layer structure can be obtained which has low crystallinity,porous surface and solid bonding with the substrate.The crystal components obtained through electrochemical mineralization and bionic natural mineralization are mainly HA,and the average grain size of HA obtained after 21 days of bionic mineralization was 15.5 nm,and average grain size of HA obtained through electrochemical mineralization was 10.4 nm.In combination with the XPS and EDS results,it can be known that the HA coating is doped with Mg and Na elements.CS was grafted to the C/C surface after going through piranha treatment,silanization treatment and glutaraldehyde treatment.After the grafting of CS on C/C,the surface of the material has a continuous,uniform and modified layer which is firmly bonded to the substrate.Combined with XPS and FTIR results,C/C surface presents a series of characteristic peaks of CS,indicating that CS was successfully bonded to the C/C surface.The contact angle of the surface of the material was also changed before and after each chemical reaction.It also proves the successful implementation of functional modification of CS on C/C.The HA modified coating was constructed on the C/C surface functionally modified by CS by means of electrochemical accelerated mineralization.The results show that the HA obtained by electrochemical mineralization is uniformly distributed on the C/C surface modified by CS.After the electrochemical mineralization of HA,the content of O element on the surface of the material increases,the content of C and N decreases,and Ca,P,Mg,Na and other elements appear.The infrared characteristic peaks of CS appeared at 1635 cm^-1,1551cm^-1,and the infrared characteristic peaks of hydroxyapatite appeared at 3460 cm^-1,1408 cm^-1,1050 cm^-1.The above results show that the CS/HA coating has successfully modified C/C.In vitro cell culture and bacteriostasis experiments showed that both CS modified C/C and CS/HA modified C/C had antibacterial activity,and the CS/HA modified C/C had better antibacterial activity than CS modified C/C.RT-PCR results showed that RUNX2,BMP-2had different genetic expressions in C/C,CS-modified C/C,CS/HA-modified C/C,HA-modified C/C.The expression of RUNX2 and BMP-2 mRNA in CS/HA modified C/C was superior to that of other groups.The above results show that CS/HA modified C/C has excellent osteogenic ability and antibacterial activity,and is promising to be used in the field of bone tissue replacement materials.