What methods are used to detect miRNAs?

To detect miRNA, various novel amplification techniques are used, which include: nanoparticle-based amplification, rolling circle amplification (RCA), hybridization chain reaction (HCR) and isothermal exponential amplification. 

In nanoparticle-based amplification, the technique involves using nanoparticles (such as gold or magnetic nanoparticles) as amplification platforms for miRNA detection. Amplification occurs when multiple nanoparticles are bound to a single miRNA, enhancing the sensitivity of detection. 

RCA utilizes a circular template and a DNA polymerase to generate long single-stranded DNA (ssDNA) products. In miRNA detection, RCA can be adapted to amplify miRNA sequences by using circularized DNA probes complementary to the target miRNA. 

Isothermal amplification techniques include loop-mediated isothermal amplification (LAMP) or nucleic acid sequence-based amplification (NASBA). These techniques use specific primer sets and enzymes to amplify miRNA sequences without the need for thermal cycling. 

HCR is a signal amplification technique that relies on the self-assembly of DNA hairpins to generate amplification cascades. In miRNA detection, HCR utilizes DNA hairpins designed to hybridize with target miRNAs and trigger a chain reaction of hybridization events, leading to the formation of long nucleic acid polymers. 

Quantitative PCR (qPCR) is also used for detecting miRNAs present at low levels in biological samples. It is highly sensitive and widely used for its ability to precisely quantify gene expression differences between samples. In qPCR, the abundance of a specific miRNA is measured by quantifying the amplification of its complementary DNA (cDNA) generated through reverse transcription.