Pseudouridine-modified RNA probe for label-free electrochemical detection of nucleic acids on 2D MoS₂ nanosheets

RNA modification, particularly pseudouridine (Ψ), has played an important role in the development of the mRNA-based COVID-19 vaccine. This is because Ψ enhances RNA stability against nuclease activity and decreases the anti-RNA immune response. Ψ also provides structural flexibility to RNA by enhancing base stacking compared with canonical nucleobases. In this report, we demonstrate the first application of pseudouridine-modified RNA as a probe (Ψ-RNA) for label-free nucleic acid biosensing. It is known that MoS₂ has a differential affinity for nucleic acids, which may be translated into a unique electronic signal. Herein, the Ψ-RNA probe interacts with the pristine MoS₂ surface and causes a change in interfacial electrochemical charge transfer in the MoS₂ nanosheets. Compared with an unmodified RNA probe, Ψ-RNA exhibited faster adsorption and higher affinity for MoS₂. Moreover, Ψ-RNA could bind to complementary RNA and DNA targets with almost equal affinity when engaged with the MoS₂ surface. Ψ-RNA maintained robust interactions with the MoS₂ surface following the hybridization event, perhaps through its extra amino group. The detection sensitivity of the Ψ-RNA/MoS₂ platform was as low as 500 attomoles, while the results also indicate that the probe can distinguish between complementary targets, single mismatches, and non-complementary nucleic acid sequences with statistical significance. This proof-of-concept study shows that the Ψ-RNA probe may solve numerous problems of adsorption-based biosensing platforms due to its stability and structural flexibility.