Photoelectrochemical immunosensor for methylated RNA detection based on WS2 and poly(U) polymerase-triggered signal amplification.

A novel photoelectrochemical immunosensor has been constructed for the determination of methylated RNA. MoS2 nanosheets with large specific area were employed as photoactive material, gold nanoparticles were used as signal amplification unit and immobilization matrix of 4-mercaptophenylboronic acid, anti-m6A antibody was adopted as methylated RNA recognition reagent, and poly(U) polymerase-mediated RNA chain extension and Ru(NH3)63+ were used as assisted signal amplification unit. With the sensitization effect of Ru(NH3)63+, the photoactivity of WS2 nanosheets was improved greatly, which also improved the sensitivity. Using visible-light excitation and ascorbic acid as electron donor, the sensitive determination of methylated RNA was achieved by monitoring the photocurrent change with different concentrations of methylated RNA. This photoelectrochemical immunosensor has a wide linear relationship with methylated RNA concentration from 0.05 to 35 nM under optimal experimental conditions. The low detection limit of 14.5 pM was realized based on 3σ criterion. In addition to the good selectivity, this sensor also presents high reproducibility with a relative standard deviation of 1.4% for the photocurrent of seven electrodes. The applicability of the developed method was also investigated by detecting the level of methylated RNA in corn seedling leaves with and without sulfadiazine treatment. Graphical abstract A novel photoelectrochemical immunosensor was developed for methylated RNA detection using the photoactive material of MoS2 and poly(U) polymerase-mediated RNA chain extension.