Labeless immunosensor assay for the stroke marker protein neuron specific enolase based upon an alternating current impedance protocol.

This paper describes the development and characterization of a label-less immunosensor for neuron-specific enolase (NSE) and its interrogation using an ac impedance protocol. Commercial screen-printed carbon electrodes were used as the basis for the sensor. Poly(1,2-diaminobenzene) was electrodeposited onto the sensors--and this modified surface was then sonochemically ablated to form an array of micropores. A second electropolymerization step was then used to deposit conductive polyaniline within these pores to give a microarray of polyaniline protrusions with diameters of several mum. This array was then utilized as a substrate to immobilize a biotinylated antibody for NSE using a classical avidin-biotin approach. Electrodes containing the antibodies were exposed to solutions of NSE and interrogated using an ac impedance protocol. The real component of the impedance of the electrodes was found to increase with increasing concentration of antigen. Control samples containing a nonspecific IgG antibody were also studied and calibration curves obtained by subtraction of the responses for specific and nonspecific antibody-based sensors, thereby accounting for and eliminating the effects of nonspecific adsorption of NSE. A linear relationship between the concentration of NSE in buffer solutions from 0 to 50 pg mL(-1) and the impedimetric response was observed.