Surface Modification Of Carbon-based Artificial Heart Valve

This study includes two aspects research on pyrolitic carbon artificial valves: one aspect aims at the surface modification on bactericidal properties. The samples are implanted by silver ions with the dose of 5×10¹⁴ ion/cm²,1×10¹⁶ ion/cm²,5×10¹⁷ ion/cm² at an energy of 70 KeV, then an Ag-rich surface layer is formed on the surface of material. The bactericidal mechanism of Ag⁺-implanted pyrolitic carbon is investigated with gram negative E. coli. Standard agar dilution method is used to test the different antibacterial effect between immediate contact and mediate contact. The results show that the bactericidal rate for both immediate contact and mediate contact increases with the ion dose; At the same ion dose, the antibacterial effect of Ag⁺-implanted pyrolytic carbon is better than its filtrate. It means that the antibacterial effect of Ag⁺-implanted pyrolytic carbon is determined by both dissolved out silver ions and undissolved complex silver ions on the surface of materials, further more the dissolved out silver ions play the more important role in killing bacteria; The bactericidal rate of the two groups approaches to 100% when the ion dose achieves 5×10¹⁷ ion/cm² (for example: sample A3).The mechanism for interactions of the Ag⁺ with E.coli's DNA was studied by UV, namely, electrostatic and base effect are exist between Ag⁺ and DNA that can destroy the natural framework of DNA molecular, so that the bactericidal effect is carried out.The second aspect involves a diamond-like amorphous carbon (DLC) film which is deposited on the surface of pyrolitic carbon values samples by magnetic Filter Cathode Vacuum Arc Deposition to modify its mechanical properties and biocompatibility. The structure, mechanical properties (such as hardness and modulus) of the DLC coated samples are investigated using Raman shifts, atomic force microscope (AFM) and nano indentation; Hemolysis and blood platelet adhesion tests are performed to text DLC films on blood compatibility. The results show that the films are the typical diamond-like amorphous carbon films (DLC), the DLC surface is homogeneous and possesses much higher hardness. So, the pyrolitic carbon samples are modified on both mechanical properties and blood compatibility. The two aspects research experimental results provide valuable data for the manufacture of artificial heart valve and it clinical application.