In-vitro blood compatibility of a-C:H:Si and a-C:H thin films

• Published in: Diamond and related materials Vol. 13; no. 4; pp. 1088 - 1092
• Main Authors: Okpalugo, T.I.T., Ogwu, A.A., Maguire, P.D., McLaughlin, J.A.D., Hirst, D.G.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.2004; Elsevier
• Subjects: Blood compatibility; Cell adhesion; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Silicon doping; Surface bond energy; Surface double layers, schottky barriers, and work functions; Blood compatibility; Silicon doping; Surface bond energy; Cell adhesion; High-frequency discharges; Endothelial cell; Work functions; Doping; Experimental study; Carbon; Silicon additions; Thin films; CVD; Growth from vapor; Compressive stress; Electronic conduction; Amorphous hydrogenated material; Preparation; Biocompatibility; PECVD; Surface energy
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2003.10.064

Carbon-based materials, for example pyrolytic carbon, have been successfully applied as artificial clinical heart valve coatings but due to ease of availability, processing, increased hardness, corrosion and scratch resistance, DLC has recently attracted attention for biomedical applications. Although often cited as having bio-compatible properties there has been little systematic study of DLC and how film structure may affect such properties. RF PECVD a-C:H and Si-doped a-C:H:Si films were deposited and in-vitro blood compatibility (haemocompatibility) investigated by the use of human microvascular endothelial cells (HMEC) on one end of the scale and platelets on the other, in order to assess the potential of DLC in biomedicine and surgical applications. Increased electronic conduction, decreased work function and decreased surface bond energy (with a high dispersive component) in the absence of graphitisation improved the blood compatibility of a-C:H and a-C:H:Si thin films. Changes in the nanostructure, surface energy and electrical properties was observed with silicon doping while thermal annealing also altered the electrical properties, reduced intrinsic compressive stress and at higher temperatures (>400 °C) induced graphitisation. Increased HMEC adhesion (approx. 6×) and/or decreased platelets aggregation (approx. 6×) is associated with lower resistivity, work function and surface energy in the thin films where there is no graphitisation. Graphitisation, however, despite the lower resistivity and work function, leads to lower HMEC adhesion and increased platelets aggregation. Si-doped a-C:H coatings deposited under optimal conditions are a significant factor in developing haemocompatible medical implants and devices.