Cell viability on functionalized diamond surfaces : towards non-invasive monitoring of cell characteristics

Abstract

In this report both qualitative and quantitative results on cell viability of Chinese hamster ovary (CHO) cells cultured on bare, well-characterized nano- and microcrystalline diamond surfaces, either hydrogen or oxygen terminated, are presented and discussed. CHO cells stably transfected with homomeric embryonic a2 glycine receptors are chosen since they offer a simplified cellular model. A systematic investigation of the viability is justified since earlier published reports are limited to more elaborate coated, single-crystal diamond surfaces. Qualitative information was derived from visual inspection of the CHO cells on the microwave plasma-enhanced chemical vapor deposited (MPE-CVD) thin diamond films - deposited on silicon - using both scanning electron microscopy and optical reflection microscopy. Compared with control glass substrates, no apparent difference existed either in cell morphology or in cell density on all substrates tested. In order to quantify these observations, other methods were applied. These consisted of different biochemical assays: the MTT cell proliferation assay (testing for proliferation and metabolic activity), the Bradford assay (total protein content), the [3H]-thymidine cell proliferation assay (proliferation) and flow cytometry (living/necrotic/apoptotic cells). Consistent with the results obtained from visual inspection, no significant differences were found using one-way ANOVA. Yet, after 7 days post seeding, the MTT result did indicate significant differences between the tested substrates. However, this is not yet reproduced. Based on these results, it can reasonably be conclude that, at least for the CHO cells used, bare nano- and microcrystalline diamond surfaces poorly affect, if at all, the growth and the viability of cultured cells. As a result, the diamond surfaces which are easiest to grow and to modify, with the best characteristics and the best shelf life, can be applied as substrate to develop non-invasive interfaces between biological cells on the one hand, and microelectronics on the other.