High Performance Biosensor Based on Electronic Transduction of Refractive Index Using 3D Nanostructured Biogenic Silica

Abstract

Various nanostructured materials have been deployed in developing biosensors. Nevertheless, achieving sub-attomolar detection limit by label free method is still challenging owing to the different noises during the sensing process. In this paper, we introduce an impedance immunosensor on freely suspended 3D nanostructured biogenic silica block, commonly called Tabashir. The working principle of this sensor is based on the electrical transduction of variations in refractive index after antigen capture. Due to the variation in refractive index, the Tabashir sensor changes the solution lining on the surface and within the pores, which has been converted to a significant variation in bulk conductivity. This screens the impedance measurement from major noise interference like the surface charge fluctuations and antibody-antigen association dissociation transients, resulting in a remarkable steady state impedance sensitivity of around 120% along with distinct shape and cut-off frequencies in the noise power spectral density (PSD) for a trace concentration of 0.1 aM Hep-B virus even in a complex mixture containing high concentration of non-specific antigen. This detection limit is an improvement by almost two orders of magnitude compared to the most sensitive label free electrical biosensor.