Photoelectrochemical monitoring of miRNA based on Au NPs@g-CN coupled with exonuclease-involved target cycle amplification.

Herein, a sensitive photoelectrochemical (PEC) biosensing platform was designed for quantitative monitoring of microRNA-141 (miRNA-141) based on Au nanoparticles@graphitic-like carbon nitride (Au NPs@g-CN) as the signal generator accompanying with T7 exonuclease (T7 Exo)-involved target cycle amplification process. Initially, the prepared Au NPs@g-CN as the signal generator was coated on the electrode surface, which could produce a strong PEC signal due to the unique optical and electronic properties of g-CN and the surface plasmonic resonance (SPR) enhanced effect of Au NPs. Meanwhile, the modified Au NPs@g-CN was also considered as the fixed platform for immobilization of S1-S2 through Au-N bond. Thereafter, the T7 Exo-involved target cycle amplification process would be initiated in existence of miRNA-141 and T7 Exo, leading to abundant single chain S1 exposed on electrode surface. Ultimately, the S3-SiO composite was introduced through DNA hybridization, thereby producing high steric hindrance to block external electrons supply and light harvesting, which would further cause a significantly quenched PEC signal. Experimental results revealed that the PEC signal was gradually inhibited with the raising miRNA-141 concentration in the range from 1 fM to 1 nM with a detection limit of 0.3 fM. The PEC biosensor we proposed here provides a valuable scheme in miRNA assay for early disease diagnosis and biological research.