Single probe-based catalytic quantum dot FRET nanosensor for human alkyladenine DNA glycosylase detection

Human alkyladenine DNA glycosylase (hAAG) is essential for repairing alkylated and deaminated bases, and it has become a prospective diagnosis biomarker and a therapeutic target for disease treatment. However, most of hAAG assays suffer from complicated reaction scheme, poor specificity, long assay time, and limited sensitivity. Herein, we report a novel single probe-based catalytic quantum dot (QD) Förster resonance energy transfer (FRET) nanosensor for simple and sensitive detection of hAAG activity. In this assay, hAAG induces the generation of 3' OH terminus via the excision of I base and the cleavage of AP site by APE1, subsequently initiating strand displacement reaction to produce numerous ssDNA signal probes. These probes can self-assemble on the QD surface to induce efficient FRET between QD and Cy5. This assay is very simple with the involvement of only a single probe for the achievement of both specific sensing and efficient signal amplification. Moreover, each signal probe contains multiple Cy5 moieties, and multiple signal probes can assemble on a single QD to greatly enhance the FRET efficiency. This nanosensor exhibits a detection limit of 3.60 × 10^-10 U/μL and it is suitable for measuring enzymatic kinetics, screening inhibitor, and quantifying cellular hAAG activity with single-cell sensitivity.