Surface and bioproperties of nanocrystalline diamond/amorphous carbon nanocomposite films

Nanocrystalline diamond/amorphous carbon (NCD/a-Q nanocomposite films have been deposited by microwave plasma chemical vapour deposition from CH4/N-2 mixtures. In order to investigate their suitability as templates for the immobilization of biomolecules, e.g. for applications in biosensors, four differently prepared surfaces, namely as-grown, hydrogen plasma treated, oxygen plasma treated, and chemically treated with aqua regia, have been thoroughly characterized by methods such as XPS, TOF-SIMS, AFM, and contact angle measurements. In addition, in order to investigate the affinity of these surface to non-specific bonding of biomolecules, they have been exposed to bovine serum albumin (BSA). It tamed out that already the as-grown surface is hydrogen terminated; the degree of the termination is even slightly improved by the hydrogen plasma treatment. Reaction with aqua regia, on the other hand, led to a partial destruction of the H-tennination. The oxygen plasma treatment, finally, causes a termination by O and OH, rather than by carboxylic acid groups. In addition, an increase Of sp(2) bonded carbon is observed. All surfaces were found to be susceptible to attachment of BSA proteins, but the coverage of the hydrogen terminated was lower than that of the O-terminated film. The highest BSA concentrations were found for the aqua regia sample where the H-termination has been removed partially. Finally, our results show that even minor surface contaminations have a great influence on the BSA coverage. (C) 2007 Elsevier B.V. All rights reserved.