Nanozyme-integrated cascade catalysis on a heterojunction for dual-mode photoelectrochemical and fluorescent platform in sensitive detection of alkaline phosphatase and its inhibitor

Alkaline phosphatase (ALP), as a crucial hydrolase in biological processes, plays a significant role in disease diagnosis and drug screening. However, conventional methods for ALP detection often suffer from limitations such as low sensitivity, complex procedures, and the requirement of sophisticated instruments, which hinder their applicability in point-of-care testing and large-scale screening. Therefore, the development of simple, highly sensitive, and reliable ALP detection platforms remains an urgent need to facilitate early diagnosis and therapeutic monitoring. In this study, a novel Ag₂S/CuO/SBOC/ITO heterojunction modified electrode was fabricated. The well-aligned energy levels among Ag₂S quantum dots (Ag₂S QDs), CuO, and sulfur-doped BiOCl (SBOC) effectively suppress the recombination of photogenerated carriers, leading to significantly enhanced photocurrent intensity and stability. Based on the synergistic effect between CuO nanoparticles (NPs) and SBOC, as well as the ascorbate oxidase-like activity of CuO NPs, an innovative dual-mode photoelectrochemical-fluorescence (PEC-FL) sensing platform was proposed for ALP activity and its inhibitors. The detection mechanism relies on ALP-catalyzed hydrolysis of L-ascorbic acid-2-phosphate trisodium salt (AAP) to generate ascorbic acid (AA) as an electron donor, which proportionally modulates the PEC response. Subsequently, the produced AA is oxidized to dehydroascorbic acid (DHAA) catalyzed by CuO NPs. DHAA then reacts with o -phenylenediamine (OPD) to yield a fluorescent product, enabling the quantification of ALP and its inhibitors via FL detection. Compared with conventional methods, this platform integrates both the photoelectric properties and nanozyme activity of CuO NPs, thereby simplifying the construction and detection procedures of the dual-mode sensors while substantially minimizing interference from electron donor oxidation and environmental factors. The cascade catalytic system comprising natural enzymes and nanozymes ensures both high sensitivity and specificity of the sensing platform. Furthermore, this strategy can be extended to monitor other enzymatic activities and inhibitors, demonstrating promising potential for clinical diagnostics and pharmaceutical development.