UNCD/a-C nanocomposite films for biotechnological applications

Ultrananocrystalline diamond/amorphous carbon nanocomposite films (UNCD/a-C) have been deposited by microwave plasma chemical vapor deposition from a 17% CH4/N2 mixture. The films consist of diamond nanocrystallites of 3-5 nm embedded in an amorphous carbon matrix of 1-1.5 nm width. In a first series of experiments it is shown that as-grown UNCD/a-C films are hydrogen-terminated, conductive and very stable. Furthermore, by plasma- and photochemical treatments the H-termination can either be improved or replaced by terminating OH or F functionalities, whereas chemical room temperature processes to change the termination failed. A second set of investigations concerns the functionalization of differently terminated UNCD surfaces. Processes are discussed to bind DNA on H-terminated UNCD and to deposit an anti-fouling poly(ethylene glycol) layer on OH-terminated films. A third series of experiments shows that UNCD surfaces are not prone to unspecific interactions with highly-fouling proteins such as bovine serum albumin (BSA) but nevertheless some interaction will take place. However, the amount of adsorption and also the ratio of BSA and fibrinogen adsorption, which is of importance for the hemocompatibility of a surface, can be adjusted by the surface termination. Finally, it will be shown that continuous as-grown UNCD surfaces are bioinert and not cytotoxic for a variety of different cell lines.