Precise and rapid solvent-assisted geometric protein self-patterning with submicron spatial resolution for scalable fabrication of microelectronic biosensors

Exponential rolling circle amplification-hybridization chain reaction (EXRCA-HCR) for AgNPs@gel-enhanced fluorescence ultrasensitive detection of miRNA-21

MicroRNA (miRNA) is a common tumor marker, whose abnormal expression is often closely related to the occurrence of various diseases. However, the conventional method for detecting miRNA is qRT-PCR, requiring additional reverse transcription steps, well-trained professionals, and expensive thermal cycling equipment. In this work, we propose a novel isothermal amplification technique (exponential rolling circle amplification-hybridization chain reaction, EXRCA-HCR) for AgNPs@gel-enhanced fluorescence specific and ultrasensitive detection of miRNA-21. This novel technique consists of rolling circle amplification (RCA), exponential isothermal amplification reaction (EXPAR) and hybridization chain reaction (HCR). Combining these three amplification methods, EXRCA-HCR provides a unique cascade amplification strategy, inheriting the advantages of linear amplification and exponential amplification. Under optimal conditions, this novel EXRCA-HCR exhibits a wide fluorescent detection range from 200 fM to 200 nM for miRNA-21, with low detection limit of 21.47 fM. By introducing AgNPs@gel, the fabricated paper-based fluorosensor based on EXRCA-HCR provides a simple and rapid visual detection of miRNA-21. This research puts forward a promising approach for detecting miRNA-21, which can be applied for early diagnosis.