Enzyme-Assisted Colorimetric Salivary miR-21 Detection by Functional Gold Nanoparticles

Abstract

miRNA-21 (miR-21) is a potential biomarker for the monitoring of diseases through its expression levels. Simple, portable and sensitive miR-21 detection of is advantageous for health monitoring in Point of Care Testing (POCT). Gold nanoparticles (AuNP) as excellent colorimetric sensors are widely used in the POCT. However, their low sensitivity is a limitation of their clinical use. Herein, we developed an AuNPs-based miR-21 assay with enzyme-assisted amplification reaction to construct the colorimetric platform capable of detecting as low as 0.1[Formula: see text]nM. In this platform, template ssDNA as a signal molecule could hybridize with ssDNA-modified AuNPs to generate the color reaction. The target miR-21 specifically hybridized to the template ssDNA, which was then cleaved by exonuclease III (Exo III) to release the target miR-21. As a trigger, miR-21 catalyzed the degradation of the template ssDNA to amplify the signal by Exo III. By hybridizing miR-21 and template ssDNA in the presence of Exo III, R-21 induced a significant decrease in the level of template ssDNA to reduce the aggregation of AuNPs. There is a clear color difference in the presence/absence of miR-21 in the assay. In this assay, the optimal concentration of templated ssDNA and Exo III were 100[Formula: see text]nM and 0.06[Formula: see text]U/[Formula: see text]L in a 100[Formula: see text][Formula: see text]L detection system. The LoD for UV–Vis spectrum and colorimetric reaction were 0.1[Formula: see text]nM and 0.5[Formula: see text]nM, respectively. The detection system has good selectivity and can be used to detect miR-21 in the simulated saliva. It has great potential for application in biomedical research as well as in clinical diagnostics.