Carbon nanotube-based label-free electrochemical biosensor for sensitive detection of miRNA-24.

The recent findings concerning the function of microRNAs (miRNAs) and the relationship between miRNA levels with specific disease highlight the need for miRNA detection. In this work, multi-walled carbon nanotubes (MWCNTs), having shown great potential for biosensors, were used to develop a simple, label-free, and sensitive electrochemical biosensor for detection of miRNA-24 by monitoring the oxidation signal of guanine. The synthetic DNA probes, being complementary with miRNA-24, were immobilized onto the surface of MWCNT-modified glass carbon electrodes by covalent cross-linking. The probes were hybridized with different concentrations of miRNA-24. The formed hybrids on the electrode surface were evaluated by differential pulse voltammetry. The change of guanine oxidation signal was observed as a result of the hybridization between the probes and miRNA-24. Control experiments using the non-complementary miRNA-29 were performed to evaluate the selectivity. Numerous factors affecting probe immobilization, target hybridization, and nonspecific binding events were optimized. Under the optimal conditions, the proposed miRNA-24 biosensor exhibits good sensitivity (4.963 μA cm(-2) decade(-1)), low detection limit (1 pM), and good selectivity and reproducibility. The biosensor also has acceptable recovery for miRNA-24 detection in complex miRNA sample.