Rapid miRNA detection enhanced by exponential hybridization chain reaction in graphene field-effect transistors

Scalable electronic devices that can detect target biomarkers from clinical samples hold great promise for point-of-care nucleic acid testing, but still cannot achieve the detection of target molecules at an attomolar range within a short timeframe (<1 h). To tackle this daunting challenge, we integrate graphene field-effect transistors (GFETs) with exponential target recycling and hybridization chain reaction (TRHCR) to detect oligonucleotides (using miRNA as a model disease biomarker), achieving a detection limit of 100 aM and reducing the sensing time by 30-fold, from 15 h to 30 min. In contrast to traditional linear TRHCR, our exponential TRHCR enables the target miRNA to initiate an autocatalytic system with exponential kinetics, significantly accelerating the reaction speed. The resulting reaction products, long-necked double-stranded polymers with a negative charge, are effectively detected by the GFET through chemical gating, leading to a shift in the Dirac voltage. Therefore, by monitoring the magnitude of this voltage shift, the target miRNA is quantified with high sensitivity. Consequently, our approach successfully detects 22-mer miRNA at concentrations as low as 100 aM in human serum samples, achieving the desired short timeframe of 30 min, which is congruent with point-of-care testing, and demonstrates superior specificity against single-base mismatched interfering oligonucleotides.