Construction Of Aptamer Based On Fluorescent Carbon Dots Aptasensor For Pesticide Residue Detection

Carbon dots is a kind of spherical zero-dimensional carbon nanomaterials with abundant functional groups on its surface,which is a new member of the nanomaterial family.Carbon dots have become a hot research direction in the field of nanomaterials because of their low toxicity,excellent biocompatibility and unique luminescence properties.With the in-depth study of carbon dots,it has been used in optoelectronics,catalysis,biological imaging and so on.Among them,the unique optical properties of carbon dots are favored by researchers.In recent years,some scholars have established the fluorescent aptasensor for the rapid detection of small molecules based on the specific recognition ability of aptamers and the unique fluorescence characteristics of carbon dots.Because of its high detection limit and excellent recognition specificity,fluorescent aptasensor have been used in medical inspection,environmental monitoring and food safety detection,and have great potential application value in many rapid detection fields.Therefore,based on fluorescent carbon dots and aptamers,two different fluorescent aptasensor were constructed based on different fluorescence quenching mechanisms of carbon dots,and they were applied to the detection of pesticide residues in food.The main research contents are as follows:(1)Based on the FRET effect between Ag NPs and the carbon dots of citric acid ethylenediamine,a novel aptamer fluorescence sensor for the detection of dimethoate was developed based on the sequence specific recognition of dimethoate by aptamer SS24-S-35.When there is no target pesticide in the sensor,aptamers can not be wrapped on the surface of Ag NPs,so Ag NPs can not be stably dispersed in high concentration Na Cl solution,then Ag NPs can not quench the carbon dots fluorescence in the sensor.The fluorescence quenching degree of the sensor was positively correlated with the concentration of dimethoate.Therefore,a fluorescent aptamer sensor for the detection of dimethoate was established.The linear detection range of dimethoate was 6~200 ?g/L,the minimum detection limit was 2.24 ?g/L,and the detection limit of dimethoate was 40 ?g/L.Further studies show that the aptamer fluorescence sensor has good specificity,and other competitive pesticides have no obvious interference on the detection of dimethoate.Moreover,the aptamer fluorescence sensor is suitable for the detection of dimethoate in real samples,and the recovery is 85.1%~105%.(2)Based on the IFE effect between Au NPs and the carbon dots of citric acid ethylenediamine,combined with the characteristics of aptamer specific recognition of carbendazim,a fluorescence aptamer sensor for carbendazim detection was established,which realized the innovation of fluorescence detection method for carbendazim pesticide.When carbendazim was not present in the detection system,aptamers encapsulated Au NPs particles were stably dispersed in the detection system,and the fluorescence signal of the sensor was in the weak fluorescence signal state by the IFE effect;When carbendazim was added to the detection system,the aptamer CZ-13 sequence preferentially combined with the target pesticide,resulting in the aggregation effect of Au NPs exposed to high concentration of Na Cl,so the fluorescence signal of the sensor was in the state of strong fluorescence signal.Therefore,we can detect carbendazim by recording the change of the fluorescence intensity of the carbon dots in the sensor.The aptamer fluorescence sensor has high selectivity for carbendazim pesticide,and can realize high sensitivity quantitative detection and visual qualitative detection of carbendazim.The detection limit of carbendazim is 6.34 ?g/L,the linear detection range is 10~200 ?g/L,and the naked eye detection limit is 100 ?g/L.The aptamer fluorescence sensor was applied to the determination of carbendazim in real samples,and the recoveries were 86%~98.7%.In this paper,carbon dots fluorescence is used as the signal element of the sensor,and aptamer is used as the recognition element of the sensor.Through the fluorescence quenching mechanism between the quenching agent and the carbon dots,two different kinds of new sensors for pesticide detection were established.The two sensors have the advantages of high sensitivity,high specificity,simple operation process and low economic cost,so they have potential application value in the rapid detection of pesticide residues.