Intercalative methylene blue as an efficient signal molecule of tremella-like Bi 2 WO 6: Toward high performance photoelectrochemical biosensing

The signaling molecule is one of the vital factors that determines the detection mechanism/strategy and the resultant performances of photoelectrochemical (PEC) bioassays. This work describes the exploration of the DNA intercalator, i.e. methylene blue (MB), as an efficient signaling molecule for high performance PEC bioanalysis. The MB can stimulate a much larger photocurrent enhancement for tremella-like Bi2WO6 than the other most often used signaling molecules, hinting its higher competence as a signaling molecule. Exemplified by carcinoembryonic antigen (CEA) as a target, we achieved homogeneous and signal-on PEC aptasensing, in which the target (CEA)-aptamer binding inhibited the subsequent rolling circle amplification (RCA) reaction, and thus regulating the release/intercalation of MB (in G-quadruplex motif) for signal stimuli. Different from most of the reported anodic PEC bioanalysis with immobilized biomolecules on photoelectrodes, this homogeneous detection not only avoids the cumbersome and costly immobilization/labelling procedure but also facilitates signal transduction, resulting from the well-preserved accessibility and molecular orientation of the biomolecules in solution. This work features the exploration of a DNA intercalator as a signaling molecule for exquisite anodic PEC bioanalysis, which may spark more interests in the exploration of numerous other DNA intercalators for advanced PEC bioanalysis.