A new ratiometric fluorescent detection of Glucose-6-phosphate dehydrogenase enzyme based on dually emitting carbon dots and silver nanoparticles

The defect of Glucose-6-phosphate dehydrogenase (G6PD) is a considerable enzyme deficiency globally and causes many diseases. Here the ratiometric fluorescent method was designed for detecting G6PD based on silver nanoparticles (AgNPs) and dually emitting carbon dots (DECDs) that exhibited dual emission fluorescence peaks in 470 and 523 (nm) under the single excitation wavelength at 330 nm. In the solution of mixed DECDs and AgNPs, the internal filter effect (IFE) causes a reduction of blue fluorescence of DECDs, because spectral overlapping happened between the emission of DECDs and the absorption of AgNPs (near 400 nm). In the absents of G6PD, the substrate of this enzyme (NADP+) was exited in the solution, causing the aggregation of AgNPs, and the absorption of aggregated AgNPs was shifted to about 520 nm. Therefore, recovering the blue fluorescence is happened. The ratiometric fluorometric assay is based on rationing the emissions (I470/I523). This method has a wide detection range (0.009–21 (U mL−1)) with a low detection limit of 0.006 (U mL−1). The assay was used to determine G6PD in spiked blood samples; the recovery values were obtained in the range of 96.19 % to 110 %. This cheap and fast method allows detecting G6PD on-site with visual detection by analyzing fluorescence color shades.