Endothelial Cell Compatibility And Preliminary Implantation Study Of Diamond-like Carbon Films For Artificial Mechanical Valve Applications

Background: Surgical heart valve replacement is an effective way to treat problem valves. Mechanical valve is the most widely used artificial heart valves in the clinical application and has good durability. It is mainly made by some biomaterials such as pyrolytic carbon and Titanium alloy and so on. Patients with mechanical valves require lifelong anticoagulation. However, bleeding, thrombosis and embolism caused by improper anticoagulation are the important impact factor for long-term survival. Therefore, to solve the coagulation problem is the central content of mechanical valve research. At present surface modification using modern thin-film technology is considered to be an effective method for better hemocompatibility of biomaterials.Objective: To investigate cytocompatibility with endothelial cells (EC), the feasibility of endothelialization, in vivo histocompatibility and hemocompatibility of diamond-like carbon (DLC) films prepared by pulsed laser deposition (PLD) for mechanical valve applications in order to get a good biocompatible coating material of mechanical valve.Methods: Part I: Cytocompatibility of DLC films with human umbilical vein endothelial cells (HUVEC). In the experimental group HUVEC were cultured on DLC films in the 24-well culture plate, whereas in the control group HUVEC were cultured alone. The supernatants were taken at 1, 3, 5 and 7 days after culture, respectively. Nitric oxide (NO) concentration in the supernatants was determined by nitric acid reductase method, and prostacyclin (PGI₂) concentration was determined by enzyme-linked immunosorbent assay (ELISA). The morphology of HUVEC in the culture plate holes of the two groups was observed using light microscope. The morphology of HUVEC on DLC films was observed using scanning electron microscopy (SEM). Part II: In vivo preliminary implantation study of DLC films for mechanical valve applications. DLC films coated mechanical valve leaflets (n = 6) and uncoated mechanical valve leaflets (n = 6) were implanted in pairs into the right atrium of six canines. The canines were terminated at 8 weeks after implantation. The extent of thrombosis and endothelial cells adhering on the surface of DLC films coated and uncoated mechanical valve leaflets were evaluated using SEM. The endocardium of the atrium contacting with the valve leaflets was observed using HE staining.Results: (1) The concentration of NO and PGI₂ secreted by HUVEC in the experimental group and control group were no significant difference (P>0.05), the secretion curve of NO and PGI2 in the two group are the same. The growth morphology of HUVEC in the two groups was unanimous by light microscope. HUVEC on the surface of DLC films showed good morphology and covered with a layer of integrated EC by SEM. (2)The surface of DLC films coated mechanical valve leaflets had no thrombosis but had endothelial-like cells adhesion by SEM. On the contrary, there were thrombosis on the surface of uncoated mechanical valve leaflets and no EC adhesion. HE staining found that DLC films coating did not cause endocardium thickening, whereas uncoated mechanical valve leaflets caused endocardium thickening.Conclusion: DLC films prepared by PLD have excellent cytocompatibility with EC and the feasibility of endothelialization. In vivo study DLC films also have good histocompatibility and hemocompatibility. Owing to good biocompatibility, DLC films can be safely used to construct the mechanical valve as a coating material.