Smartphone-based photoelectrochemical immunoassay of prostate-specific antigen based on Co-doped Bi₂O₂S nanosheets

Portable and on-site detection of target biomarker is of great significance in early diagnosis of diseases. Herein, we designed a portable smartphone-based PEC immunoassay platform to detect prostate specific antigen (PSA) adopting Co-doped Bi₂O₂S nanosheets as photoactive materials. The fast photocurrent response under visible light and excellent electrical transport rate invest Co-doped Bi₂O₂S with the property of being effectively excited even under a weak light source. Therefore, with the incorporation of a carriable flashlight that act as the excitation light source, disposable screen-printed electrodes, a microelectrochemical workstation and a smartphone that served as control center, point-of-care analytical detection of low-abundance small molecule analytes was successfully realized. Specifically, a sandwich-type immunoreaction was performed using alkaline phosphatase labeled secondary antibody as signal indicator. In the presence of PSA, ascorbic acid as generated through a catalytic reaction, resulting in the enhancement of photocurrent intensity. The photocurrent intensity increased linearly with the logarithm of PSA concentrations ranging from 0.2 to 50 ng mL^-1 with a detection limit of 71.2 pg mL^-1 (S/N = 3). This system provided an effective method for the construction of portable and miniaturized PEC sensing platform for the application of point-of-care health monitoring.