A GQD-MnO₂ nanocomposite-based fluorescence assay for sensitive detection of the Bcl-2 gene

We developed a novel fluorescence detection method utilizing graphene quantum dots (GQDs) and manganese dioxide (MnO₂) nanocomposites to enhance the sensitivity and specificity of in vitro monitoring of Bcl-2 gene expression, a key factor in tumor survival and treatment resistance. This method leverages the interplay between reduced glutathione (GSH) and hairpin DNA structures (H1 and H2) to simulate a cellular environment, enabling the redox-mediated disintegration of MnO₂ nanosheets and the release of GQDs, restoring fluorescence. The presence of the Bcl-2 gene triggers a catalytic hairpin assembly (CHA) reaction, amplifying the Cy3 fluorescence signal and achieving a detection limit of 20.7 pM. The system showed high specificity and stability, validated through control experiments with various DNA sequences. Optimization of key parameters, including MnO₂ nanosheet concentration, GSH levels, and the ratio of hairpins H1 and H2, was critical for maximizing assay performance. The MnO₂ nanosheets quench GQD fluorescence and act as carriers for DNA probes, which are released upon reduction by GSH, mimicking intracellular redox conditions. The CHA reaction further amplifies the signal, allowing sensitive detection of low target gene levels. This biosensing platform integrates the unique properties of GQDs and MnO₂ nanosheets, offering a real-time, sensitive, and selective method for monitoring Bcl-2 gene expression. This approach holds significant promise for early cancer diagnosis and personalized treatment strategies.