Label-less Immunosensor Assay for Myelin Basic Protein Based upon an ac Impedance Protocol

This paper describes the development and characterization of a label-less immunosensor for myelin basic protein (MBP) and its interrogation using an ac impedance protocol. Commercial screen-printed carbon electrodes were used as the basis for the sensor. Polyaniline was electrodeposited onto the sensors, and this modified surface then utilized to immobilize a biotinylated antibody for MBP using a classical avidin−biotin approach. Electrodes containing the antibodies were exposed to solutions of MBP 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 were obtained by subtraction of the responses for specific and nonspecific antibody-based sensors, thereby accounting for and eliminating the effects of nonspecific adsorption of MBP. A logarithmic relationship between the concentration of MBP in buffer...