Employment of electrostriction phenomenon for label-free electrochemical immunosensing of tetracycline.

The presented work describes a simple label-free electrochemical immunosensor for the determination of tetracycline (TC). The functioning of the sensor was based on the electrostriction of a antibody-terminated thiol layer self-assembled on a gold electrode surface, serving as a dielectric membrane. The intensity of electrostriction was correlated with the amount of TC captured through an affinity reaction with its specific antibody, and was followed in the form of capacitance-potential curves. The process of the immunosensor construction was optimized using electrochemical impedance spectroscopy (EIS). The chemisorption time of the thiol, the duration of the TCAb immobilization and its concentration were optimized. The developed immunosensor exhibited a linear response in two concentration ranges: from 0.95 to 10 μmol L-1 and from 10 to 140 μmol L-1, with the mean sensitivity of 6.27 nF μmol-1 L (88.67 nF μmol-1 L cm-2) and 0.56 nF μmol-1 L (7.84 nF μmol-1 L cm-2), respectively. The limit of detection was evaluated as 28 nmol L-1. The specificity of the proposed sensor toward other antibiotics, amoxicillin and ciprofloxacin, was examined. The immunosensor was successfully employed to quantify TC in a tablet form and in a matrix of river water.