Multi-mode label-free biosensor based on methylene blue sensitized C3N4/BiVO4 heterostructure for ultrasensitive detection of miRNA-122

In this work, a multi-mode label-free biosensor based on methylene blue (MB) sensitized C3N4/BiVO4 heterostructure was proposed to achieve ultrasensitive detection of miRNA-122. It was found that MB had a strong photosensitization effect on BiVO4 for the first time, but the adsorption interaction of MB on BiVO4 surface was poor. Therefore, a C3N4/BiVO4 heterostructure with Π-Π conjugate effect was constructed by electrostatic reaction, achieving a large amount of MB adsorption. The photoelectric sensitization amplitude of C3N4/BiVO4 reached two orders compared with pure BiVO4. Moreover, C3N4 displayed excellent electrochemiluminescence (ECL) signals at both negative and positive potentials. It was unexpectedly found that MB could effectively absorb luminescence of C3N4 at positive potential, and an astonishing quenching efficiency reached 98.4 %. In addition, MB can be widely used for electrochemical detection. Therefore, when MB was entrapped in mesoporous silica nanoparticles (MSNs), and capped by DNA, target miRNA-122 can trigger quantitative release of MB. So this work could realize multi-mode detection including photoelectrochemistry (PEC), ECL and differential pulse voltammetry (DPV) by using MB. This biosensor was simple, fast, convenient and accurate, which was promising for biochemical analysis, food safety, and other fields.