Isothermal chemiluminescent assay based on circular stand-displacement polymerization reaction amplification for cel-miRNA-39-3p determination in cell extracts

Ultrasensitive fluorescence microRNA biosensor by coupling hybridization-initiated exonuclease I protection and tyramine signal amplification

Tyramine signal amplification (TSA) has made its mark in immunoassay due to its excellent signal amplification ability and short reaction time, but its application in nucleic acid detection is still very limited. Herein, an ultrasensitive microRNA (miRNA) biosensor by coupling hybridization-initiated exonuclease I (Exo I) protection and TSA strategy was established. Target miRNA is complementarily hybridized to the biotin-modified DNA probe to form a double strand, which protects the DNA probe from Exo I hydrolysis. Subsequently, horseradish peroxidase (HRP) is attached to the duplex via the biotin-streptavidin reaction and catalyzes the deposition of large amounts of biotin-tyramine in the presence of hydrogen peroxide (H2O2), followed by the conjugation of signal molecule streptavidin-phycoerythrin (SA-PE), which generates an intense fluorescence signal upon laser excitation. This method gave broad linearity in the range of 0.1 fM - 10 pM, yielding a detection limit as low as 74 aM. An increase in sensitivity of 4 orders of magnitude was observed compared to the miRNA detection without TSA amplification. This biosensor was successfully applied to the determination of miR-21 in breast cancer cells and human serum. By further design of specific DNA probes and coupling with the Luminex xMAP technology, it could be easily extended to multiplex miRNA assay, which possesses great application potential in clinical diagnosis.

Chemiluminescent plate assay of microRNA-155 coupled with catalytic hairpin assembly with oligonucleotide release (CHAOR)

A heterogeneous sensitive microRNA-155 assay based on a new isothermal amplification method, called catalytic hairpin assembly with oligonucleotide release (CHAOR), was developed. The principle of CHAOR was studied by non-denaturing electrophoresis. To detect the amplification product, a polyperoxidase-streptavidin conjugate (molar ratio 1:80) and an enhanced chemiluminescence reaction were used, which made it possible to increase assay sensitivity. The detection limit of microRNA-155 assay was 0.4 pM. The coefficient of variation of the chemiluminescent signal, formed upon the heterogeneous determination of miRNA-155, was less than 12 % within the working range. The efficiency of CHAOR as an amplification method was similar to that of traditional CHA, as miRNA-155 assays based on CHAOR and CHA had similar analytical parameters. In addition, the proposed assay was highly specific. Contrary to traditional CHA, CHAOR, one of whose products is a single-stranded oligonucleotide, can be used in analytical methods based on cascade amplification.

miRNA Detection for Prostate Cancer Diagnosis by miRoll-Cas: miRNA Rolling Circle Transcription for CRISPR-Cas Assay

Micro-RNA (miRNA) emerges as a promising type of biomarker for cancer diagnosis. There is an urgent need for developing rapid, convenient, and precise miRNA detection methods that may be conducted with limited laboratory facilities, especially in underdeveloped areas. Herein, we developed a miRNA detection method termed miRoll-Cas, where miRNA is first amplified by rolling circle transcription and then subject to CRISPR-Cas13a assay. Using miRoll-Cas, we realized the sensitive detection of multiple cancer-relevant miRNA markers (miR21, miR141, and Let7b) and specifically identified other variants of the Let7 family, which can accurately discriminate prostate cancer patients from healthy people. We envision that miRoll-Cas may be readily translated to clinical applications in the diagnosis of a variety of diseases beyond cancer.

Quantitation of MicroRNA-155 in Human Cells by Heterogeneous Enzyme-Linked Oligonucleotide Assay Coupled with Mismatched Catalytic Hairpin Assembly Reaction

In the present work, we describe the development of a chemiluminescent enzyme-linked oligonucleotide assay coupled with mismatched catalytic hairpin assembly (mCHA) amplification for the quantitative determination of microRNA-155. To improve its sensitivity, a polymerase-free mCHA reaction was applied as an isothermal amplification method. The detection limit of the proposed assay was 400 fM. In addition, the high specificity of the assay was demonstrated. The proposed assay allowed assessment of the content of microRNA-155 in human cancer lines such as HepG2, Caco2, MCF7, and HeLa. The quantitation of microRNA-155 was performed after purification of short RNAs (less than 200 nt) from cell lysates since a high matrix effect was observed without this pre-treatment. The results of the quantitative determination of the microRNA content in cells were normalized using nematode microRNA-39, the concentration of which was determined using a heterogeneous assay developed by us using a strategy identical to that of the microRNA-155 assay.

Modern Methods for Assessment of microRNAs

The review discusses modern methods for the quantitative and semi-quantitative analysis of miRNAs, which are small non-coding RNAs affecting numerous biological processes such as development, differentiation, metabolism, and immune response. miRNAs are considered as promising biomarkers in the diagnosis of various diseases.

Comparison of chemiluminescent heterogeneous and homogeneous–heterogeneous assays coupled with isothermal circular strand-displacement polymerization reaction amplification for the quantification of miRNA-141

A heterogeneous and homogeneous–heterogeneous chemiluminescent microplate assay was developed for the determination of miRNA-141 levels in human cells.