ATP-triggered release of methylene blue for amplified photoelectrochemical bioanalysis: Enabling a split-type immunosensing platform for the detection of CA15-3.

To meet the clinical need for detecting the breast cancer biomarker CA15-3, and to overcome the drawbacks of traditional detection methods such as operational complexity, high cost, and insufficient sensitivity, a highly sensitive split-type photoelectrochemical (PEC) immunosensing platform was developed. Specifically, Bi2O3/BiOBr/Ag nanocomposite were used as the substrate, in which the separation and migration of photogenerated charge carriers were effectively promoted by the internal electric field and the electron-bridge effect of Ag, thereby markedly enhancing the photocurrent response. Furthermore, during the immunorecognition process, ZIF-90 encapsulated MB was used as a secondary antibody label. When ATP triggered the collapse of ZIF-90, methylene blue was released, and the reversible redox reaction system with p-nitrophenol (p-NP) accelerated the transfer of interfacial electrons, thereby increasing the cathodic photocurrent intensity and detection sensitivity. The immunosensor exhibited a wide linear range from 0.001 to 100 U/mL, with a low detection limit of 0.00063 U/mL. This PEC platform provides a simple, sensitive, and reliable strategy for tumor marker detection, holding great potential for clinical diagnostics.