Ratiometric Fluorescence Determination of Avian Influenza a Virus Subtype H1N1 DNA with Functionalized Quantum Dots and Gold Nanoparticles

A new type of ratiometric fluorescence sensor based on DNA functionalized quantum dots (DNA-QDs) and gold nanoparticles (AuNPs) was constructed for sensitive fluorescence determination of the avian influenza A virus subtype H1N1 DNA. Using the nucleic acid strand displacement reaction, the carboxyfluorescein-DNA (FAM-DNA) replaced DNA-QDs on the surface of DNA-AuNPs, so that the fluorescence of QDs increased and the fluorescence of FAM decreased. In the presence of H1N1 DNA, the ends of the DNA on the AuNPs-DNA-QDs conjugates were blocked, preventing strand displacement. The fluorescence intensity ratio of FAM to QDs (F₅₂₀/F₆₂₄) was proportional to the concentration of H1N1 DNA. The linear range was from 2.5 to 20.0 nM with a limit of detection of 0.52 nM. Furthermore, this sensor showed good selectivity. This strategy is a simple, accurate, and sensitive tool to detect DNA biomarkers.