Trace and Label-Free MicroRNA Detection Using Oligonucleotide Encapsulated Silver Nanoclusters as Probes

Abstract

A simple, sensitive, and label-free method for microRNA (miRNA) biosensing was described using oligonucleotide encapsulated silver nanoclusters (Ag-NCs) as effective electrochemical probes. The functional oligonucleotide probe integrates both recognition sequence for hybridization and template sequence for in situ synthesis of Ag-NCs, which appears to possess exceptional metal mimic enzyme properties for catalyzing H(2)O(2) reduction. The miRNA assay employs gold electrodes to immobilize the molecular beacon (MB) probe. After the MB probe subsequently hybridizes with the target and functional probe, the oligonucleotide encapsulated Ag-NCs are brought to the electrode surface and produce a detection signal, in response to H(2)O(2) reduction. An electrochemical miRNA biosensor down to 67 fM with a linear range of 5 orders of magnitude was obtained. Meanwhile, the MB probe allows the biosensor to detect the target with high selectivity. The Ag-NCs-based approach provides a novel avenue to detect miRNA with high sensitivity and selectivity while avoiding laborious label and signal amplification. It is convinced that rational introduction of signal amplification strategy to the Ag-NCs-based bioanalysis can further improve the sensitivity. To our best knowledge, this is the first application of the electrocatalytic activity of Ag-NCs in bioanalysis, which would be attractive for genetic analysis and clinic biomedical application.

Ag nanoclusters could efficiently quench the photoresponse of CdS quantum dots for novel energy transfer-based photoelectrochemical bioanalysis

“…And Fig. 1D demonstrated the amplified spectrum of the Ag NCs, the peaks at 403 and 480 nm were consistent with the literature results (Dong et al, 2012), indicating the generation of ultrasmall Ag NCs.…”

An electrochemical ELISA-like immunosensor for miRNAs detection based on screen-printed gold electrodes modified with reduced graphene oxide and carbon nanotubes

“…To develop highly sensitive miRNA biosensors, e.g. bioanalytical tools able to detect miRNA below the nanomolar level, many strategies based on nanomaterials have been applied, using graphene (Dong et al, 2012a), silicon nanowires (Yang et al, 2009;Zhang et al, 2009), gold nanoparticles (Roy et al, 2011;Yin et al, 2012), silver nanoclusters (Dong et al, 2012b) or conducting polymer/carbon nanotube hybrids (Tran et al, 2013b). For example, Zhang et al (2009) have developed a label-free electrochemical biosensor based on silicon nanowires.…”

Electrochemical sensing of microRNAs: Avenues and paradigms

“…The product of the enzymatic reaction, α-naphthol, was electrochemically oxidized at þ23 V vs. Ag/AgCl which allowed for a sensitive analysis of miRNA with a detection limit of 0.67 mg mL À 1 . In 2012, Dong and his coworkers reported a voltammetric biosensor based on oligonucleotide encapsulated silver nanoclusters (Ag-NCs) (Dong et al, 2012). In this work, a SAM of a molecular beacon (MB) probe was formed onto a gold electrode surface.…”