Simultaneous photoelectrochemical and visualized immunoassay of β-human chorionic gonadotrophin

Herein, on the basis of the alkaline phosphate (ALP) induced reaction, a simultaneous photoelectrochemical (PEC) and visualized immunoassay has been established for the detection of beta-human chorionic gonadotrophin (beta-HCG). Specifically, in the proposed system, ALP stimulated the oxidative hydrolyzing transformation of 5-bromo-4-chloro-3-indoyl phosphate (BCIP) to an indigo precipitation, generating an insulating layer that impeded the interfacial mass and electron transfer and thus the photocurrent production. Meanwhile, a visualized detection could be performed according to the change of color intensity. Upon proper experimental conditions, the protocol possessed a detection range of 0.5-1000 IU/L with a detection limit of (0.20 +/- 0.011) IU/L toward beta-HCG. With high sensitivity and specificity, this work presents the first general protocol for simultaneous PEC and visualized detection, which could be easily extended to addressing numerous other targets. (C) 2016 Elsevier B.V. All rights reserved.