Preparation Of Peroxidase Mimetic Carbon Quantum Dots And Its Applications In Body Fluid Analysis

Firstly,the research progress and current situation of mimetic peroxidase were summarized.The advantages of carbon quantum dots(CQDs)mimetic enzymes were compared and discussed.Some traditional detection methods of glucose,glutathione and sarcosine in body fluid were introduced.CQDs with peroxidase mimetic properties were synthesized from natural substances in this paper.Combined with oxidation of 3,3',5,5'-tetramethylbenzidine(TMB)and etching of gold nanorods,a new method for the detection of glucose and glutathione in serum,glucose and sarcosine in urine was constructed,and the detection conditions were explored.The specific experiments are as follows:(I)CQDs were prepared from soot or litchi peel by cleaning,nitric acid reflux,neutralization,dialysis,vacuum drying and characterized by infrared spectroscopy and transmission electron microscopy.In the presence of H2O2,CQDs can catalyze the formation of ox-TMB from TMB,which indicates that the synthesized CQDs have the characteristics of peroxidase mimetic enzymes.(2)A new method for colorimetric determination of glucose in urine by TMB oxidation with CQDs as peroxidase mimetic enzyme was established.The basic principle is that under aerobic conditions,glucose is oxidized to gluconic acid and hydrogen peroxide through the catalysis of glucose oxidase.Under the catalysis of CQDs,hydrogen peroxide oxidizes TMB to produce colour reaction.The effects of temperature and pH value on the catalytic performance were studied.The results showed that the linear range of glucose detection in 0.025-0.40 mM with detection limit of 5.10 p.M at pH 3.5,35?,0.5 mM TMB and 1?g·mL-1 CQDs.Common interfering substances in urine did not interfere with the determination.The recovery of standard addition in actual urine was 95.0%-105.1%.The analytical performance of the method met the requirements of microanalysis.(3)A new method for the determination of glutathione in serum by TMB oxidation colorimetry was established.The CQDs peroxidase mimic enzyme could catalyze the oxidation of TMB to form oxygen ox-TMB with characteristic absorption peak at 652 nm in the presence of hydrogen peroxide.It was found that the introduction of GSH could inhibit the formation of ox-TMB,resulting in a decrease in absorbance at 652 nm.On this basis,a high sensitive colorimetric method for glutathione detection was developed.The effects of different experimental variables such as pH,temperature,H2O2,CQDs and TMB concentration on the analytical performance of the method were systematically examined.A good linear relationship was found in the range of 0.05-20?M of GSH concentration,and the detection limit was 0.016?M.The method was successfully applied to the determination of glutathione in human serum with a recovery of 95.7%-103.6%.(4)Gold nanorods(GNRs)exhibit strong local surface plasmon resonance in the visible or near infrared region,and are widely used in colorimetric analysis.In this chapter,a colorimetric method for the determination of glucose by etching gold nanorods with CQDs as a peroxide mimetic enzyme was proposed.Glucose oxidase catalyzes the oxidation of glucose to hydrogen peroxide,and catalyzes the oxidation of-to I2 by hydrogen peroxide with CQDs.Because the tip of gold nanorods has a high reactivity,the gold nanorods are etched along the longitudinal direction by I2,and therefore the longitudinal absorption wavelength of gold nanorods is blue-shifted.Under the optimum conditions,the linear relationship between ?W and glucose concentration was good in the range of 0.01-2.0 mM(?W=W0-W,W0 and W are the maximum absorption wavelength before and after etching,respectively),and the detection limit was 0.003 mM.More importantly,this method has potential application value in the determination of glucose in human serum.(5)A colorimetric method for the determination of sarcosine by etching GNRs and using CQDs as peroxide mimetic enzyme was proposed.The oxidation of sarcosine to hydrogen peroxide catalyzed by sarcosine oxidase and the oxidation of I-to I2 by hydrogen peroxide catalyzed by CQDs resulted in the etching of gold nanorods along the longitudinal direction and the blue shift of their maximum absorption wavelength.Under the optimum conditions,the linear range in 0.01-0.8?M and the detection limit was 0.033?M.Satisfactory results were obtained in the determination of sarcosine in human urine by this method.