A DNA--silver nanocluster probe that fluoresces upon hybridization

Area of Science:

• Nanotechnology
• Biochemistry
• Molecular Diagnostics

Background:

• DNA-templated silver nanoclusters (DNA/Ag NCs) are novel fluorophores with potential advantages over quantum dots and organic dyes.
• Existing DNA detection probes often rely on Förster energy transfer (FRET) for quenching, which can limit signal-to-background ratios.
• Guanine-rich DNA sequences are known to influence the optical properties of nearby nanomaterials.

Purpose of the Study:

• To investigate the fluorescence enhancement of DNA/Ag NCs in proximity to guanine-rich DNA.
• To develop a novel DNA detection probe (NanoCluster Beacon, NCB) based on this fluorescence enhancement.
• To demonstrate the efficacy of NCBs for sensitive and specific molecular detection, such as for influenza targets.

Main Methods:

• Synthesized DNA/Ag NCs and studied their fluorescence properties.
• Explored the effect of guanine-rich DNA sequences on DNA/Ag NC fluorescence.
• Designed and implemented a NanoCluster Beacon (NCB) probe for target detection.
• Performed separation-free assays to evaluate NCB performance against conventional probes.

Main Results:

• Observed a 500-fold red fluorescence enhancement of DNA/Ag NCs near guanine-rich DNA.
• Developed NCBs that exhibit a 'lights up' signal upon target binding, independent of FRET quenching.
• Achieved high signal-to-background (S/B) ratios (>100) with NCB detection.
• Demonstrated NCB detection of an influenza target with an S/B ratio of 175 in a separation-free assay.

Conclusions:

• The proximity-induced fluorescence enhancement of DNA/Ag NCs by guanine-rich DNA enables a new class of highly sensitive probes.
• NanoCluster Beacons offer superior performance (e.g., 5-fold higher S/B ratio) compared to conventional molecular beacons.
• This detection technique is simple, cost-effective, and compatible with standard DNA synthesis, paving the way for accessible molecular diagnostics.