Label-Free Platform for MicroRNA Detection Based on the Fluorescence Quenching of Positively Charged Gold Nanoparticles to Silver Nanoclusters

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Abstract
A novel strategy was developed for microRNA-155 (miRNA-155) detection based on the fluorescence quenching of positively charged gold nanoparticles ((+)AuNPs) to Ag nanoclusters (AgNCs). In the designed system, DNA-stabilized Ag nanoclusters (DNA/AgNCs) were introduced as fluorescent probes, and DNA-RNA heteroduplexes were formed upon the addition of target miRNA-155. Meanwhile, the (+)AuNPs could be electrostatically adsorbed on the negatively charged single-stranded DNA (ssDNA) or DNA-RNA heteroduplexes to quench the fluorescence signal. In the presence of duplex-specific nuclease (DSN), DNA-RNA heteroduplexes became a substrate for the enzymatic hydrolysis of DNA strand to yield a fluorescence signal due to the diffusion of AgNCs away from (+)AuNPs. Under the optimal conditions, (+)AuNPs displayed 95% of the quenching efficiency to AgNCs, which paved the way for ultrasensitive detection with a low detection limit of 33.4 fM. In particular, the present strategy demonstrated excellent specificity and selectivity toward the detection of target miRNA against control miRNAs, including mutated miRNA-155, miRNA-21, miRNA-141, let-7a, and miRNA-182. Moreover, the practical application value of the system was confirmed by the evaluation of the expression levels of miRNA-155 in clinical serum samples with satisfactory results, suggesting that the proposed sensing platform is promising for applications in disease diagnosis as well as the fundamental research of biochemistry.
Funding Information
  • Government of Jiangsu Province
  • National Natural Science Foundation of China (21305053, 21675067)
  • Priority Academic Program Development of Jiangsu Higher Education Institutions

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