Study On Biodetection Of Antibiotics And Enzymes Based On Graphene Quantum Dots And Nanogolds

Graphene quantum dots(GQDs)are graphene nanoparticles with a size of less than 100 nm,which have good conductivity,adjustable fluorescence properties,and low toxicity and other characteristics,so they are widely used in the field of sensing detection.Nanogolds is nanomaterials with a size range of 1 nm-100 nm,which can be divided into gold nanoparticles(AuNPs),gold nanocluster(AuNCs),gold rods and gold sheets.In addition to possessing the three special effects of general nanomaterials,nanogold also has special photoelectric properties and good biocompatibility,so it has a good application prospect in catalysis,biosensing and other fields.Based on the properties of GQDs and nanogolds,this study established three types of biological sensing system for the analysis the concentration of levofloxacin,lysozyme,and pepsin.The specific research as follows:(1)GQDs-AuNPs with excellent photoelectric properties were synthesized by chemical conjugation method.The GQDs-AuNPs were characterized by fluorescence spectroscopy(FS),Ultraviolet-visible absorption spectroscopy(UV-Vis),High-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD),and other methods.The results show that the lattice spacing of GQDs-AuNPs is 0.26 nm,which has excitation independent photoluminescence characteristics.The surface of GQDs-AuNPs contains functional groups such as hydroxyl and carboxyl groups.Based on the optical characteristics of GQDs,AuNPs and GQDs-AuNPs,biological sensing system for detecting levofloxacin(LVFX)was established.Under the optimal detection conditions,LVFX has an enhanced effect on the fluorescence of GQDs and GQDs-AuNPs,and the difference of fluorescence intensity has a good linear relationship with the concentration of LVFX.In addition,LVFX has certain influence on the ultraviolet absorbance of AuNPs and GQDs-AuNPs,and there is a good linear relationship between the A330/A520 ratio and the concentration of LVFX.These three detection systems have lower limit of detection(LOD)and higher sensitivity.The LOD are respectively 2.3×10-8mol·L-1(GQDs),7.1×10-8 mol·L-1(AuNPs),1.4×10-8 mol·L-1(fluorescence detection of GQDs-AuNPs)and 6.9×10.8 mol·L-1(UV detection of GQDs-AuNPs).In the actual samples,the recovery rate was good,ranging from 96.2 to 102.7%,and the relative standard deviation(RSD)was low,in the range of 1.0 to 2.7%.Therefore,biological sensing system based on GQDs,AuNPs and GQDs-AuNPs have high accuracy in detecting LVFX and can be used for the analysis of actual samples.This study provides a certain foundation for the application of GQDs-AuNPs in the field of biosensing analysis,and provides a theoretical basis for the detection of relevant antibiotics in medicine and ecological environment.(2)Based on the inner filter effect(IFE)of AuNPs and GQDs,a new method to detect the content of lysozyme was established.Under the optimal detection conditions,lysozyme combines with AuNPs,making the IFE effect between AuNPs and GQDs weaken,and subsequently restoring the fluorescence intensity of GQDs.The difference in fluorescence intensity is related to the concentration of lysozyme(0.0～6.33×10-8 mol·L-1)has agood linear relationship.The LOD is 2.7×10-9 mol·L-1,with a recovery rate in the range of 97.0 to 98.4%,and RSD between 2.1 and 4.2%.(3)AuNCs with red fluorescence were prepared using Chicken Egg White(CEW)as template,and CEW-AuNCs were characterized by HRTEM,UV-Vis,FS,XRD and other methods.Using CEW-AuNCs as fluorescent probes,a fluorescent biological sensing system was developed for the selective detection of pepsin(PEP)in real samples.Under the optimal detection conditions,PEP has a quenching effect on the fluorescence intensity of CEWAuNCs,and the difference in fluorescence intensity of CEW-AuNCs has a linear relationship with the concentration of PEP(0.0～1.44×10-5 mol·L-1),and the LOD is 9.0×10-8 mol·L-1.In the actual sample,the recovery rate is within the range of 99.0～102.4%,and the RSD is between 3.0～4.2%.