Impedimetric immunosensor with on-chip integrated electrodes for high-throughput screening of liver fibrosis markers

This paper deals with an immunoassay based on microelectromechanical system (MEMS) technology with integrated electrochemical cells on a chip and locally copolymerized semi-insulating membrane of poly o-phenylenediamine (PPD) with antibodies. The hepatic fibrosis marker lamin (LN) and its antibody anti-lamin (alpha-LN) are selected to illustrate the functionality of the sensor. MEMS technology endows this sensor with the features of a small size, a high reproducibility, a low cost, and the potential integration with IC circuitry for portable applications. The sensor is characterized by impedance spectroscopy and calibrated by cyclic voltammetry. The active-site density is found to be directly related to the copolymerization cycles and antibody concentration. The results show that controlling the current in the range from -16 to -13 mu A at 0.8 V provides the optimized semi-insulation characteristic that is most suitable for all detections. The impedance analysis reveals that a low-frequency measurement for concentration-dependent impedance is applicable for such a sensor. The evaporation of the electrolyte is found to be responsible for the impedance changes at a very high frequency. The sensitivity of the immunosensor to LN is 0.6208%/(ng/mL) with a linear detection concentration range between 0 and 90 ng/mL.