Au nanoparticles/SnO2/ZnIn2S4-based biosensor for photoelectrochemical/electrochemical dual-signal detection of RNase A by combining the enzymolysis of DNA probe and the generation of molybdophosphate precipitate

Abstract

We report here photoelectrochemical/electrochemical dual-signal detection of ribonuclease A (RNase A) by integrating the enzymolysis of a DNA probe with the generation of molybdophosphate precipitate. SnO2 nanoparticles-decorated ZnIn2S4 nanosheets as a novel photoactive material output a photocurrent higher than SnO2 and ZnIn2S4 alone resulting from the improved electron-hole separation. The modification of Au nanoparticles (AuNPs) on SnO2/ZnIn2S4 can not only enable facile immobilization of a ribonucleotide uracil (rU) containing single strand DNA probe but also boost the photocurrent exciton-plasmon coupling effect. The rU-DNA probe is immobilized on the AuNPs/SnO2/ZnIn2S4-based photoelectrode to construct a biosensor. The immobilized rU-DNA probe is cleaved by RNase A and then incubated with molybdate. When RNase A is present, the DNA chain becomes shorter, and less molybdophosphate precipitates are formed on the electrode. The hindrance of interfacial electron transfer by molybdophosphate precipitate enables “signal-on” photoelectrochemical detection of RNase A, with a linear range from 1 to 104 pg mL−1 and a detection limit of 0.2 pg mL−1. In addition, the electroactivity of molybdophosphate precipitate enables “signal-off” electrochemical detection of RNase A, with a linear range from 10 to 5 × 103 pg mL−1 and a detection limit of 2 pg mL−1. This work not only develops an efficient photoactive material but also offers a reliable detection of RNase A in photoelectrochemical/electrochemical dual mode.