Ultrasensitive electrochemical biosensor for detection of microRNA-155 as a breast cancer risk factor.

Due to the stability of microRNAs (miRNAs) in serum and other body fluids, they are known as promising cancer biomarkers. Recent studies have indicated higher expression of miRNA-155 (miR-155) in patients with breast cancer compared to healthy people. In the present report, a rapid and sensitive electrochemical biosensor has been developed for detection of miR-155 as a breast cancer risk factor. At first, a thiolated probe was immobilized on the gold electrode surface. Then, the target (miR-155) was exposed to the probe. In the next step, the positively charged polyethyleneimine-silver nanoparticles as electroactive labels were absorbed onto the negatively charged probe-target hybrid. In the third step, the anodic peak current which was produced due to the oxidation of silver nanoparticles was recorded as the electrochemical signal. The designed biosensor provided an ultrasensitive method for the detection of miR-155 with the detection limit of 20 zmol and a wide linear range from 2 × 10-20 to 2 × 10-12 mol. Moreover, the biosensor was able to detect miR-155 in real serum samples with satisfactory results.