Patterning of the surface termination of ultrananocrystalline diamond films for guided cell attachment and growth

The surface patterning of a biomaterial, i.e. placing areas with different surface chemistries next to each other is an important step for various biomedical and biotechnological applications, e.g. in biosensor technology, drug screening or tissue engineering. In the current work we investigated the patterning of the surface termination of ultrananocrystalline diamond (UNCD) films prepared by microwave plasma chemical vapor deposition. In order to achieve a high wettability contrast in the neighboring areas O- and F-terminations were selected. The sequence of the modifications and the feasibility of different masking techniques were tested in advance. Based on the achieved results the following process of surface patterning was applied. Initially the whole UNCD surface was modified by UV/O3 treatment rendering the surface O-terminated and strongly hydrophilic (contact angle against water of 11°). The partial masking of this surface before the second modification was achieved with a gold hard mask photolithographically structured and wet etched in form of a grid. After the second modification with CHF3 plasma which provided F-termination and hydrophobic character of the surface (contact angle > 110°), the gold layer was removed. The results of the patterning of the surface termination were visualized by scanning electron microscopy revealing different contrasts of the areas with different terminations. Finally, human SH-SY5Y neuroblastoma cells were plated on the patterned UNCD surfaces and they exhibited preferential attachment and growth on the hydrophilic grid.