A nanozyme-based competitive electrochemical immunosensor for the determination of E-selectin

A nanozyme-based competitive electrochemical immunosensor has been developed for the quantitative determination of E-selectin, a common adhesion molecule expressed by activated endothelial cells. A glassy carbon electrode modified with poly(azure A) and E-selectin antibody (GCE/PAA/Ab) was prepared. Au-CuO nanocomposite-labeled E-selectin, CD62E-Au-CuO, was synthetized, and it could be captured on GCE/PAA/Ab owing to the immunoreaction. The immobilized nanocomposites on GCE/PAA/Ab/CD62E-Au-CuO acted as nanozymes and were involved in the electrocatalytic process that caused the high cathodic peak current. The assembly of GCE/PAA/Ab/CD62E-Au-CuO was inhibited by E-selectin due to the competitive immunoreaction, which resulted in a decrease of the current signal. The cathodic peak current difference at - 0.35 V vs SCE was proportional to the concentration of E-selectin in the range 0.500-500 ng mL^-1, and the limit of detection was estimated to be 226 pg mL^-1. The cell morphology observation, the cell viability test, and the electrochemical measurement indicate that the injury of human umbilical vein endothelial cells was aggravated, and the release of E-selectin from the injured cells was gradually accelerated when the NaCl content in the growth medium increased.