Enhancing fluorescent response of immunosensing by a DEP chip with transparent electrodes and microcavities array

Abstract

Dielectrophoresis (DEP) has been demonstrated the manipulations of bio-modified particles for biosensors, and the microelectrodes are mostly made of metal materials such as Au, Cu and Pt, etc. However, the metal electrodes could induce extra background noise as observed the DEP chip in a fluorescence microscope. Currently, the fluorescence response still dominates the indicators of immunoassays; therefore, it's important to eliminate the extra background noise of fluorescence response form metal electrodes for an immunosensor. In this study, a DEP chip was utilized to immobilize the nanoprobes in a microcavities array for immunosensing. A transparent conductive material, Indium Tin Oxide (ITO), was employed in the fabrication of DEP electrodes, and the fluorescence responses of DEP chip with transparent (ITO) electrodes were compared with identical DEP chip with conventional Au electrodes during immunoassay. According to experimental results, the enhancement of fluorescence response of DEP chip with ITO electrodes was greater than the values of DEP chip with Au electrodes about 1.57 times and 1.44 times for the immunosensing of 10 nM and 1 nM BSA, respectively. In addition, by applying the DEP force during the immunosensing, the fluorescence response was also enhanced due to the BSA can be condensed by DEP force. The DEP condensation was more significant for immunosensing at low BSA concentration. Consequently, we have demonstrated a DEP chip with transparent ITO electrodes and the background noise of fluorescence response can be eliminated to enhance the sensitivity of immunosensing.