A new label-free fluorescent sensor for human immunodeficiency virus detection based on exonuclease III-assisted quadratic recycling amplification and DNA-scaffolded silver nanoclusters.

A label-free and sensitive fluorescence biosensing platform for human immunodeficiency virus gene (HIV-DNA) detection has been fabricated based on luminescent DNA-scaffolded silver nanoclusters (DNA/AgNCs) and autonomous exonuclease III (Exo III)-assisted recycling signal amplification. One long-chain DNA (X-DNA) molecule can hybridize with two assistant DNA (F-DNA) molecules and one HIV-DNA molecule; after Exo III digests X-DNA to liberate F-DNA and HIV-DNA. F-DNA combines with P-DNA (template of DNA/AgNCs), accordingly, P-DNA is cut and the fluorescence of the system is quenched. This assay can finish in one-step without any labelling of the DNA chain or complex construction, and the strategy is sensitive with the detection limit as low as 35 pM. At the same time, the approach exhibits good selectivity even against a single base mismatch. What's more, the method is able to monitor HIV-DNA in real human serum samples; it holds great potential for early diagnosis in gene-related diseases.