Bilirubin oxidase labeling triggers an efficient signaling mechanism of oxygen reduction reaction for smart photocathodic immunoassay

Abstract

Abstract Photocathodic immunoassays show brilliant prospect for practical detection in biological matrix owning to the inherent strength against signal interference from potential reductive molecules. However, their exploration with advanced and efficient signaling mechanism is still barren. We herein report an enhanced photocathodic immunoassay via utilizing bilirubin oxidase (BOD) labeling to trigger an illustrious signaling mechanism of oxygen reduction reaction (ORR). The target model of prostate-specific antigen (PSA, Ag) was employed to exemplify this platform. Typically, the fabricated NiO/CdSe/Au hybrid photocathode served as the substrate to anchor capture antibody (Ab1). In order to increase host loading, abundant BOD molecules were labeled on signal antibody (Ab2) with the assistance of carbon nanotube (CNT), forming the Ab2-BOD/CNT conjugate. When specific immunological recognition occurred, the BOD labeling could efficiently catalyze the reduction reaction of electron acceptor of dissolved oxygen, causing dramatically promoted cathodic photocurrent signal. By introducing this ingenious signaling mechanism triggered by BOD, enhanced photocathodic immunoassay with high sensitivity and accuracy in biological matrix was developed. This work pioneers an effective but general strategy for the design of advanced photocathodic bioassays for different targets of interest.