Digital count of antibodies through differential impedance for high-resolution immunosensing

This paper presents a biosensing system for antibody detection based on Differential Impedance Sensing by nanobead amplification able to perform high resolution measurements down to few beads counts. The sensor exploits a biochemical surface functionalization stack of a Copoly layer housing a synthetic peptide probe for IgG antibody. A pair of closely designed gold interdigitated micro-electrodes (IDE) in a differential configuration, one as reference and the other as active sensor, ensures rejection of drift in solution temperature and ionic content in every instant of the protocol and counteracts all possible common mode mismatches. The biosensor has shown performances with a limit of detection (LOD) below 100 pg/ml concentration of the primary antibody diluted in buffer. An electronic reading board developed as an expansion platform for an XEM6310 FPGA module, performs multifrequency lock-in impedance time tracking at high resolution in a portable configuration. The proposed system holds promise for rapid and specific detection of selected antibody with clinically relevant concentrations for rapid immunotesting in a point of care setting.