Alkaline phosphatase-responsive anodic electrochemiluminescence of CdSe nanoparticles

Alkaline phosphatase (ALP) catalyzes the hydrolysis and transphosphorylation of a wide variety of phosphoric acid monoesters and plays an important role in clinical diagnosis. In this work, an ALP-responsive anodic electrochemiluminescence (ECL) system based on coreaction of CdSe nanoparticles (NPs) and triethylamine has been designed for facile detection of ALP. The substrate of ALP, i.e., phenyl phosphate salt, shows no effect on the ECL emission whereas its catalytic product of phenol may induce ECL inhibition. For the buffer containing phenyl phosphate, the ECL emission is found to decline in the presence of ALP with different incubation time. The mechanism investigations indicate that the deposition of the electropolymerized phenol products may compete with the electrophoretic-driven adsorption of CdSe NPs on glassy carbon electrode and induce the ECL inhibition, which can be demonstrated by scanning electron microscopy, energy dispersive spectrometry, and anodic stripping voltammetry. Therefore, an inhibition type strategy has been developed to sensitively detect ALP ranging from 0.5 to 6.4 nM (activity ca. 2-25 U/L), with a detection limit of 0.5 nM. The potential interference from the common proteins is negligible. The recovery of ALP in diluted serum samples ranges from 91 to 114%, implicating its potential applications in the complex biological matrixes.