A photocurrent-polarity-switching biosensor for highly selective assay of mucin 1 based on target-induced hemin transfer from ZrO hollow spheres to G-quadruplex nanowires.

Herein, a photocurrent polarity switching platform for highly selective assay of mucin 1 (MUC1) was developed based on target-induced hemin transfer from ZrO hollow spheres (ZrO HSs) to G-quadruplex nanowires (G wires). In this system, SiO spheres were used as templates to synthesize the uniform and mesoporous ZrO HSs. As nanocontainers, ZrO HSs could load hemin in its cavity via pores. Then, the aptamers of MUC1, as bio-gates, blocked the pores of ZrO HSs based on the specific binding of Zr and the phosphate groups of aptamer. In the presence of MUC1, the aptamer could specifically recognize and bind with MUC1, and then leave away from the surface of ZrO HSs, which resulted in the opening of the bio-gates and releasing of hemin. Assisted with the G wires formed on the Au NPs/InS/ITO, the released hemin was captured on the electrode through the formation of hemin/G-quadruplex structure, leading to the switch of the photocurrent polarity of the electrode from anodic photocurrent to cathodic photocurrent. The proposed photoelectrochemical biosensor showed outstanding performance for MUC1 assay with high selectivity, wide linear response range (1 fg mL -10 ng mL) and lower detection limit (0.48 fg mL). And the strategy could be easily extended to a triple-mode detection of MUC1 because the hemin/G-quadruplex structure was widely used in electrochemical and colorimetric methods as a hydrogen peroxide mimetic enzyme, which might provide wide applications in biological or clinical studies.