The cysteine-induced BiOBr as a novel photoactive material with high photoelectric efficiency for ultrasensitive detection of microRNA

In this work, cysteine-induced BiOBr (cys-BiOBr) was prepared as a novel photoactive material with high photoelectric efficiency to construct a photochemical (PEC) biosensor for ultrasensitive detection of microRNA-155 (miRNA-155). Impressively, the photocurrent signal of cys-BiOBr showed an increase of 6 times compared to that of individual BiOBr, since the doping of S not only narrowed the band gap to enhance light absorption and accelerate carrier separation, but also augmented the surface oxygen vacancy concentration for preventing electron-hole pairs recombination, resulting in the obvious improvement of photoelectric efficiency. Furthermore, through exponential amplification reaction (EXPAR), a few miRNA-155 could be derived into abundant steady G-quadruplexes for immobilizing hemin to form the G-quadruplex/hemin complex for catalyzing H2O2 decomposition to significantly amplify photocurrent signal. The proposed PEC biosensor performed a wide range from 0.5 fM to 1 nM with a detection limit of 0.13 fM. This strategy provided a new method to prepare the highly efficient photoactive material for sensitive detection of biomolecules and exhibited enormous potential in early clinical diagnosis.