Probing the Influence of Crosslinking Layer Incubation Time on the Performance of Non-Faradaic Impedimetric Biosensors

Abstract

Non-faradaic impedimetric biosensors have received a wide interest due to their direct detection approach. The crosslinking layer in these biosensors has to be dense to avoid permeation of ions into the electrode to allow direct detection of diseases. In this work, we investigate, for the first time, the effect of incubation time of cysteamine crosslinking layer on non-faradaic impedimetric biosensors performances. Two sets of interdigitated gold electrodes were functionalized with cysteamine for 1 h and 24 h. Then, UL83-antibodies were immobilized on the surface via glutaraldehyde for the detection of human cytomegalovirus. The sensitivity of biosensors functionalized with cysteamine for 24 h were superior to those functionalized with cysteamine for 1 h (i.e. 0.046 nF/ln(ng ml −1 ) compared to 0.0224 nF/ln(ng ml −1 )). Probing the cysteamine layer with faradaic-EIS and X-ray photoelectron spectroscopy suggests that the better biosensing performance of biosensors incubated in cysteamine for 24 h is related to the better coverage of cysteamine at the biosensor surface. Atomic force microscopy analysis also revealed an increase in surface roughness with increasing cysteamine incubation time which resulted in better biosensing performances due to the enlarged surface area. Non-faradaic impedimetric biosensors received attention recently due to their redox-free nature and simple circuitry. The intermediate crosslinking layer plays a major role on the performance of non-faradaic impedimetric biosensors. This work investigates the effect of short and prolonged cysteamine incubation time on the performance of biosensors. Longer incubation time leads to denser cysteamine crosslinking layer and hence better sensing performances.