▎ 摘　　要

NOVELTY - A fluorescent aptasensor is prepared by (s1) configuring citric acid and thiourea solution according to ratio, stirring, heating to obtain nitrogen-sulfur co-doped graphene quantum dots (N, S-GQDs) solid, measuring solid and low-density lipoprotein aptamer (LDLApt), stirring to obtain nitrogen-sulfur co-doped graphene quantum dot-low-density lipoprotein aptamer (N, S-GQDs-LDLApt) solution, (s2) weighing reduced graphene oxide (rGO) and adding N,N-dimethylamide (DMF) in ultrasonic cell disruptor to make a dispersion, adding ferric oxide in ethanol to obtain ferric oxide-reduced graphene oxide dispersion, mixing with sulfur co-doped solution, and heat-preserving, (s3) adding different concentrations of LDL solutions to LDL fluorescent aptasensor, heat-preserving, and calculating the minimum detection limit of the method, and (s4) adding actual sample to LDL fluorescent aptasensor, heat-preserving, and calculating the concentration of LDL in sample to be tested to working curve of LDL. USE - Fluorescent aptasensor for constructing low-density lipoprotein protein detection in serum. ADVANTAGE - The method is simple in operation, low in cost and has low detection limit of 1.29 ng/mL. The fluorescent aptasensor using the excellent fluorescence quenching ability of ferric iron-reduced graphene oxide (Fe3O4-rGO) composite and high fluorescence intensity of nitrogen-sulfur co-doped quantum dots (N, S-GQDs), LDL aptamers can specifically recognize and bind LDL proteins, and can specifically and quantitatively detect LDL protein is constructed to detect the content of LDL in serum. DETAILED DESCRIPTION - A fluorescent aptasensor is prepared by (s1) configuring citric acid and thiourea solution according to ratio, stirring, heating, cooling, and drying to obtain nitrogen-sulfur co-doped graphene quantum dots (N, S-GQDs) solid, measuring solid and low-density lipoprotein aptamer (LDLApt), stirring and mixing to obtain nitrogen-sulfur co-doped graphene quantum dot-low-density lipoprotein aptamer (N, S-GQDs-LDLApt) solution, (s2) weighing reduced graphene oxide (rGO) and adding N,N-dimethylamide (DMF) in ultrasonic cell disruptor to make a dispersion, adding ferric oxide (Fe3O4) in ethanol and using ultrasonic cell disruption to make dispersion liquid, mixing the two dispersions, heating and stirring, and drying to obtain ferric oxide-reduced graphene oxide (Fe3O4-rGO) powder, weighing powder, adding ultrapure water to constant volume, placing in ultrasonic cell crusher, and crushing until powder is dispersed in ultrapure water to obtain ferric oxide-reduced graphene oxide (Fe3O4-rGO) dispersion, mixing graphene dispersion with sulfur co-doped solution, heat-preserving at rest to quench fluorescence of the nitrogen-sulfur co-doped graphene quantum dots (N, S-GQDs) to form low-density lipoprotein (LDL) fluorescent aptasensor, scanning with a fluorescence spectrophotometer, fixing the excitation wavelength at 368 nm, measuring the fluorescence intensity at 450 nm, and recording as F0, (s3) adding different concentrations of LDL solutions to LDL fluorescent aptasensor and heat-preserving, scanning with a fluorescence spectrophotometer, fixing the excitation wavelength at 368 nm, measuring the fluorescence intensity at 450 nm, and recording as F1, using (F1-F0)/F0as ordinate, and LDL concentration as abscissa, drawing the working curve, and calculating the minimum detection limit of the method, and (s4) adding actual sample to LDL fluorescent aptasensor in step (s2), heat-preserving, scanning with a fluorescence spectrophotometer, fixing the excitation wavelength at 368 nm, and recording the fluorescence intensity at 450 nm, and calculating the concentration of LDL in sample to be tested to working curve of LDL obtained in step (s3).