Interdigitated microelectrode arrays based on non-cytotoxic a-Si_xC_1-x:H for E. coli detection

Fabrication and testing of interdigitated microelectrode arrays whose structure includes non-cytotoxic hydrogenated amorphous silicon-carbon alloy (a-Si_xC_1-x:H) as the surface to be biofunctionalized for capturing enteropathogenic Escherichia coli (E. coli, EPEC) are presented. a-Si_xC_1-x:H films were obtained by enhanced chemical vapor deposition (PECVD). The extract method was used to assess the cytotoxicity of the films. The design of the PIMAs includes two layers of a-Si_xC_1-x:H, one intrinsic layer deposited onto silicon dioxide (SiO2) before evaporating titanium (Ti), and one doped layer deposited onto the Ti-microelectrodes. Electrical impedance spectroscopy (EIS) was used to know the effects of the biofunctionalization layer, conductivity of the medium and any capture of bacteria by antibodies on the microelectrodes. According to the results, the high hydrogen dilution contributes to low incorporation of CH_n groups improving the non cytotoxicity of the films, and the capture of bacteria on the microelectrodes improves the sensitivity. It manifests itself as a shift of the low cutoff frequency (F_low) of the impedance spectrum to the right, allowing the device to sense at frequencies lower than F_low. A percentage change in impedance of 1600% at 100 Hz was obtained after 5 minutes in contact with medium with EPEC concentration of 8.5 × 10⁸ CFU/mL.