Reserch Of Composite/Structure And Biocompatibility Of Carbon Films

Artificial hip joint replacement is the most direct and effective treatment of advanced hip joint disease. The metal-on-metal (MOM) type is eSPecially suitable for young and active patients because of the unique advantage of using large size femoral head. However, metal debris and metal ions can be generated due to the wear and corrosion process, which would induce osteolysis and aseptic loosening. In order to resolve the problems caused by wear debris, methods to reduce the wear of MOM joints have been widely investigated.Diamond like carbon (DLC) film is deemed to be a promising solution of MOM joints aseptic loosening since DLC coating is hard, wear resistant and chemically inert. As DLC stands for a group of carbon films, the biological property of various DLCs may be different due to different composition and microstructure, which is determined by the fabrication method and deposition parameters. Hence, DLC films with different composition and microstructure are fabricated and the relationship of composition/microstructure and biocompatibility are researched in this article to promote the clinical application of DLC film.The microstructure and physical characteristics of the films are investigated by Raman SPectroscopy, contact angle measurement, atom force microscopy (AFM), electrokinetic analysis, electrical resistivity measurement and Hall effect measurement. Bovine serum albumin (BSA) and serum protein adsorption are used to evaluate the protein adsorption ability of DLC films. Macrophages are cultured to evaluate the inflammation reaction, and osteoblasts adhesion and growth are also evaluated.The results show that the composition and microstructure of DLC film have great impact on the wettability, surface energy and electrical properties, which further influence the behavior of macrophages and osteoblasts.The a-C:H film is deposited by electron convolute resonance plasma enhanced chemical vapor deposition (ECR-PECVD) and a-C film is fabricated by magnetic filtered cathodic vacuum arc (MFCVA). The results show that more osteoblasts adhere on a-C:H film because of the higher surface energy than a-C film. However, a-C film has a higher SP2 content and is N type semiconductor with unpaired electrons. Protein adsorption assay shows that the a-C film can covalently bind more serum proteins than a-C:H film. The unpaired electrons of a-C film contribute to its better ability to covalently bind bioactive proteins than a-C:H film, and the superior adsorption and bioactivity of the adhesive proteins on a-C film further induce the better biological performance of a-C film. In a word, a-C film induce lower inflammatory reaction and higher ostoblasts viability than a-C:H film.The a-C films with different microstructure are fabricated by controlling the bias voltage. Pulsed bias induces higher SP2 content and higher surface energy while direct current induce higher SP3 content and lower surface energy. The results show that more osteoblasts adhere on the film with higher surface energy. As the protein form a uniform adsorption layer that is good for osteoblasts proliferation, osteoblasts on a-C film fabricated by pulsed bias show higher viability.In order to further investigate the influence of H on biocompatibility of DLC film, a-C is treated by H plasma. H treatment induces higher SP3 content and lower surface energy, which is adverse to osteblasts adhesion and cell viability.In a word, DLC films with higher SP2 content show better biocompatibility than that with higher SP3 content. In addition, H treatment induces higher SP3 content and is adverse to osteblasts growth.