Selective cholesterol assay using peroxidase-like iron-copper Co-doped nitrogen carbon quantum dots in colorimetric...

Effective disease management and diagnosis rely on monitoring biomarkers such as cholesterol in bodily fluids. This study presents iron and copper-coordinated nitrogen-doped carbon quantum dots (FeCu@NCQDs) synthesized via a straightforward hydrothermal method, exhibiting a notable photoluminescence quantum yield of 39.09 %. With fluorescence emission at 450 nm under 330 nm excitation, FeCu@NCQDs are ideal for sensitive biosensing. A detection probe combining FeCu@NCQDs, 4-aminoantipyrine, and phenol was developed. In the presence of cholesterol oxidase-generated H₂O₂, 4-aminoantipyrine, and phenol reacted to produce a pink compound that quenches FeCu@NCQDs' fluorescence through an inner-filter effect, enabling fluorometric detection. Colorimetric detection is achieved by measuring this compound's absorbance at 515 nm. The FeCu@NCQDs' peroxidase-like activity, enhanced by Fe and Cu, facilitates this process. Under optimized conditions, the fluorometric and colorimetric methods exhibited linear detection ranges of 0.03-600 μM and 0.13-600 μM, respectively. This dual-mode system effectively detected cholesterol in serum samples with high accuracy and recovery, offering a sensitive, reliable, and economical tool for clinical diagnostics and personalized health monitoring.