CoOOH nanosheets-coated g-C3N4/CuInS2 nanohybrids for photoelectrochemical biosensor of carcinoembryonic antigen coupling hybridization chain reaction with etching reaction

A signal-on photoelectrochemical (PEC) biosensor was successfully established for the sensitive monitoring of carcinoembryonic antigen (CEA) by using copper indium disulfide-sensitized graphitic-like carbon nitride (g-C3N4/CuInS2) as the photosensitive material and cobalt oxyhydroxide (CoOOH) as the light-blocking material, coupling target-triggered hybridization chain reaction (HCR) with hydrolysate-induced dissolution/etching of CoOOH nanosheets. Initially, a sandwiched reaction occurred between capture aptamer-conjugated magnetic bead and trigger aptamer in the presence of CEA. Then, the carried trigger aptamer initiated HCR between two hairpin sequences to produce long double-helix strand for capturing alkaline phosphatase. The generated ascorbic acid reduced/etched CoOOH nanosheets into divalent cobalt ions, which decreased the amount and thickness of CoOOH and exposed the underlying g-C3N4/CuInS2, thus leading to a distinct increase in the photocurrent. Under optimum conditions, PEC sensor showed high sensitivity toward CEA with a dynamic range of 0.02-40 ng mL(-1) and a detection limit of 5.2 pg mL(-1). Also, it possessed favorable selectivity, high stability as well as good precision. The accuracy of PEC approach was well consistent with commercial CEA ELISA kit. These exceptional analytical performances of PEC biosensor indicated that it might have a broad application prospect in the diagnosis of CEA.