Ultrasensitive electrochemical biosensor for microRNA-377 detection based on MXene-Au nanocomposite and G-quadruplex nano-amplification strategy

MicroRNAs (miRNAs) are considered as potential biomarkers for early diagnosis and prognostic assessment of diabetic nephropathy. In this work, an electrochemical biosensor for ultrasensitive detection of miRNA-377 was constructed based on MXene-Au nanocomposites and G-quadruplex nano-amplification strategy. As a promising nanocarrier, taking advantage of leveraging synergistic effects between Au nanoparticles (AuNPs) and MXene nanosheet, MXene-Au nanocomposites exhibited excellent electronic conductivity and provided massive active sites for DNA capture probe immobilization by Au-S bonds. AuNPs modified with Guanine-rich sequence DNA detection probes were designed as signal amplification nano-labels. Specifically, by inducing the transition of Guanine-rich detection probes to G-quadruplex, the strong affinity interaction between methylene blue and G-quadruplex could not only reflect trace concentration information of miRNA-377, but also lead to the further enhancement of electrochemical signal (2.7-fold). As a result, this newly designed biosensor exhibited superior sensing performance with a wide linear range from 10 aM to 100 pM and the limit of detection was as low as 1.35 aM. Compared with biosensors based on other nanocomposites and reported miRNA-377 biosensors, the pro-posed sensing platform did not require any thermal cycling or reverse transcription process, meeting the miRNA sensing requirements of convenient, sensitive, specific and stable. Furthermore, the as-constructed biosensor also displayed good selectivity, which was applied to accurate detection of miRNA-377 in human serum samples with satisfactory sensitivity, suggesting the biosensor system has promising applications in biological researches and early clinical diagnosis for diabetic nephropathy.