A novel signal amplification tag to develop rapid and sensitive aptamer-based biosensors.

Determination of microRNAs (miRNAs) as valuable blood-borne biomarkers has attracted many scientific attentions. However, analytical methods are still restricted by miRNAs intrinsic characteristics. In this study, for the first time, novel blackberry-like magnetic DNA/FMMA nanospheres were synthesized and mounted on a gold stir-bar as signal amplification probes. To produce this strong electrochemical signal label, double strand DNAs were immobilized on gold coated magnetic nanospheres through a hybridization chain reaction followed by reversible addition-fragmentation chain-transfer polymerization, which brought a great quantity of the electroactive tags (FMMA) on the nanosphere surface. These nanospheres were then fixed on the gold stir-bar as signal probes. The magnetic DNA/FMMA nanosphere probes can be released by substituting with the newly emerging DNA fragments of catalyzed hairpin assembly products. Eventually, these signal probes were magnetically enriched on the electrode surface to produce electrochemical signal and finally, the biosensor was developed to detect miRNA-106a (model target). The suggested aptamer-based biosensor demonstrated considerable selectivity, acceptable storage stability, high specificity, and excellent performance in real sample analysis without any pretreatments. As a result, current study reveals that the developed strategy has a great potential for the early diagnosis of gastric cancer and additionally the clinical monitoring of any miRNA sequences.