Exploration of photoelectrochemical immunosensing and quench-type signal amplification strategies based on oxygen-rich vacancy ternary FeCoCuOx nanostructures

Alpha-fetoprotein (AFP) is a key biomarker for the early diagnosis of hepatocellular carcinoma, while traditional detection methods often lack the required sensitivity and simplicity for the point-of-care testing. Herein, an innovative photoelectrochemical (PEC) immunoassay based on ternary FeCoCuOx nanostructures with abundant oxygen vacancies was developed for highly sensitive AFP detection. The engineered metal oxide provided an efficient photoactive interface, facilitating enhanced charge separation and light harvesting. In the sensing process, target AFP was specifically recognized by immobilized mAb1, followed by the binding of a signal probe (ALP-AuNP-pAb2: ALP and anti-AFP secondary antibody-labeled gold nanoparticle), which introduced alkaline phosphatase (ALP) into the system. ALP catalyzed the hydrolysis of 2-phospho-L-ascorbic acid (AAP) to generate ascorbic acid (AA), which acted as an electron donor under light irradiation and quenched the cathodic photocurrent by reacting with photoexcited holes. The PEC sensor achieved a low detection limit of 34.1 pg mL−1 and a broad linear range from 0.05 to 50 ng mL−1. The superior performance was attributed to the synergistic enhancement from ALP-mediated signal amplification and the multimetallic oxide interface. This work demonstrates a robust and selective PEC platform with strong clinical potential for cancer biomarker detection.