Fluorescence Method Used For Detection Of Glucose And Ochratoxin A In Agricultural Products

The food nutrition and food safety is closely related to the development of national economy and people's live.It is essential to detect various materials quickly and sensitively which related to human health and food safety.However,there are some problems for the traditional detection methods,e.g.,instrumental or antibodies-based methods,like complicated operation,time-consuming and high cost,etc.Therefore,it is very important to develop simple,fast,high-efficient and accurate detection methods for protecting people's physical and mental health.Here,on account of the development of new nanomaterials and fluorescence sensing technology,three fluorescence methods had been constructed and used for detecting glucose and ochratoxin a?OTA?based on fluorescent carbon quantum dots?CQDs?.?1?A novel dual fluorometric and colorimetric method was developed for glucose detection by using MnO₂ nanosheets and CQDs.The CQDs could adsorb onto the surface of MnO₂ nanosheets through the electrostatic interaction,which induced the fluorescence quenching of CQDs by fluorescence resonance energy transfer effect.The H₂O₂ intermediates could be produced by the oxidation of glucose by glucose oxidase?GOD?,which further resulted in the decomposition of MnO₂ nanosheets,accompanied with the brown color MnO₂ nanosheets changed to colorless Mn²⁺ions,and the absorption of the solutions decreased,consequently.Meanwhile,CQDs could also be redispersed in the solution,which resulted in the fluorescence signal of the solution recovered as well.The linear detection ranges of glucose were 5-1000?M by fluorescent method and 20-600?M by colorimetric method.The limits of detection of these two methods were 2.11 and 2.18?M,respectively.This method had the advantages,like simple operation,resonable sensitivity and selectivity.The accuracy of glucose detection could be improved by using these two kinds of signal output methods,the versatility of glucose detection method could be improved as well.Our method had also been successfully applied for determining the glucose concentration in human serum.?2?A novel double magnetic separation assisted fluorescence method had been developedforrapidlydetectingOTAinwheatandcornsamples.Aptamer-functionalizedmagneticnanomaterials?Fe₃O₄NPs-Aptamer?and complementaryDNAconjugatednitrogen-dopedgraphenequantumdots?NGQDs-cDNA?were firstly prepared,due to the hybridization reaction between aptamer and cDNA,NGQDs-cDNA could bind to Fe₃O₄ NPs-Aptamer to form complex,which resulted in the fluorescence quenching of NGQDs by fluorescence resonance energy transfer effect.After the addition of OTA into the solution,the specific interaction between OTA and aptamer could induce the separation of DNA double strands,and the release of the NGQDs-cDNA into the solution,which further resulted in the recover of the fluorescence signal of NGQDs.To reduce the intensity of background signal and improve the sensitivity of OTA detection,double magnetic separation processes were conducted to remove the unreacted NGQDs-cDNA and Fe₃O₄ NPs in the mixture.The linear detection range of OTA was 10 nM to 2000 nM,and the detection limit was 0.66 nM.This method had good selectivity and feasibility for the actual agricultural samples detection.?3?Sensitively detection of OTA by using aptamer functionalized nitrogen doped graphene quantum dots?NGQDs-Aptamer?as fluorescence probes,magnetic porous carbon?MPC?as separation matrix,and exonuclease I?Exo I?to amplify the detection signal.Since the?-?interaction between aptamer and MPC,the NGQDs-Aptamer could be adsorbed on the MPC,which resulted in the fluorescence quenching of the NGQDs-Aptamer.Due to the strong interaction between OTA and aptamer,the addition of OTA could result in the detachment of NGQDs-Aptamer from MPC,in accompanied with the recovery of fluorescent intensity.The Exo I could specifically digest the aptamer in NGQDs-Aptamer-OTA complex,the released OTA could futher interact with another NGQDs-Aptamer on the MPC and induced more NGQDs released in the solutions,therefore,the fluorescence intensity could be enhanced significantly.The linear detection range of OTA was 10 to 5000 nM with a limit of detection as 2.28 nM.The method could also be applied for the detection of actual samples.