Surface energy, wettability, and blood compatibility phosphorus doped diamond-like carbon films

There is an increasing interest in developing novel coatings to improve the biocompatibility of cardiovascular implants. In this work, we fabricated phosphorus-doped (P-doped) diamond-like carbon (DLC) films by plasma immersion ion implantation and deposition (PIII and D) and the structure, physicochemical characteristics, electrical properties, as well as surface biomedical compatibility, were evaluated using different characterization techniques. Microstructures manifesting as dots are visible under optical microscopy while atomic force micrographs disclose that these round and flat islands are distributed evenly on the film surface. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) results show that they are composed of C, P and O while only C and O can be found in the areas away from the islands. Attenuated total-reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy indicates the presence of many POx and CPxOx species. In the Raman spectra, the G peak of the P-doped sample shifts to a lower wave-number suggesting that the film is more disordered. The P-doped DLC film exhibits excellent wettability (16.9° water contact angle). In vitro platelet adhesion and coagulation factor experiments were conducted to examine the blood compatibility. Scanning electron microscopy (SEM) and optical microscopy reveal a significant decrease of the number as well as activation of platelets on the P-doped DLC film.