Effects of protein inter-layers on cell-diamond FET characteristics


Diamond is recognized as an attractive material for merging solid-state and biological systems. The advantage of diamond field-effect transistors (FET) is that they are chemically resistant, bio-compatible, and can operate without gate oxides. Solution-gated FETs based on H-terminated nanocrystalline diamond films exhibiting surface conductivity are employed here for studying effects of fetal bovine serum (FBS) proteins and osteoblastic SAOS-2 cells on diamond electronic properties. FBS proteins adsorbed on the diamond FETs permanently decrease diamond conductivity as reflected by the −45 mV shift of the FET transfer characteristics. Cell cultivation for 2 days results in a further shift by another −78 mV. We attribute it to a change of diamond material properties rather than purely to the field-effect. Increase in gate leakage currents (by a factor of 4) indicates that the FBS proteins also decrease the diamond–electrolyte electronic barrier induced by C–H surface dipoles. We proposed a model where the proteins replace ions in the very vicinity of the H-terminated diamond surface.

Schematic model of the interface between surface conductive diamond SG-FET channel and the cell medium containing proteins and cells. Schematic electric field distribution and characteristic dimensions across the interface are shown along the right side.