An enzyme-free surface plasmon resonance biosensor for real-time detecting microRNA based on allosteric effect of mismatched catalytic hairpin assembly

MicroRNAs (miRNAs) play significant regulatory roles in a variety of diseases and have been emerging as a group of promising biomarkers in cancer cells. Here, a novel and simple surface plasmon resonance (SPR) biosensor was developed for specific and highly sensitive detection of target miRNA employing the mismatched catalytic hairpin assembly (CHA) amplification coupling with programmable streptavidin aptamer (SA-aptamer). The presence of target miRNA triggered the allosteric effect of CHA amplification, which brought about the recycling of the target miRNA and produced large amounts of CHA products and activated SA-aptemers. Meanwhile, the plentiful CHA products could hybridize with the capture probes on the sensor chip, and the massive activated SA-aptamers could capture the streptavidin to achieve enhancement and output of the detection signal. Benefiting from the outstanding performance of the enzyme-free CHA amplification and non-label SPR biosensor, the established biosensor exhibited simplified process, high sensitivity and good selectivity. Under the optimal conditions, this designed strategy could detect target miRNA down to 1 pM with a dynamic range from 5 pM to 100 nM, and was successfully applied to the determination of target miRNA spiked into human total RNA samples. Thus, this SPR-based biosensor might become a potential alternative tool for miRNA detection in medical research and early clinical diagnosis.