IN-VITRO STUDIES OF DLC COATINGS WITH SILICON INTERMEDIATE LAYER

In vitro studies have been carried out using three cell culture lines, to investigate the biocompatibility of diamond-like carbon (DLC) coat ed discs. The thin film samples have been produced on glass substrates with an intermediate layer of amorphous hydrogenated silicon (a-Si:H) to improve the adhesion of the carbon layer. An r.f. plasma chemical vapour deposition technique has been used, with silane SiH4 and n-buta ne as source gases for the a-Si:H and a-C:H (DLC) layers respectively. Mouse macrophages, human fibroblasts and human osteoblast-like cells have been grown on the DLC/a-Si:H coated and control (uncoated) discs for periods of up to 72 h. Lactate dehydrogenase (LDH) assays carried out at 24, 48 and 72 h have provided a measure of cell viability and h ave shown no evidence of overt cytotoxicity. No difference in LDH rele ase between the DLC (with a-Si:H bonding layer) and control specimens has been observed. Further, the absence of abnormal cellular morpholog y has been demonstrated by optical microscopy. This work indicates a g ood degree of biocompatibility for DLC coatings which incorporate an i ntermediate layer of amorphous hydrogenated silicon to improve the adh esion of the DLC layer to the underlying substrate material.