Construction And Detection Application Of Fluorescent Carbon Quantum Dot Aptasensor System Based On Inter Filter Effect

Carbon dot is a new type nano-material composed of graphitized carbon core and amorphous carbon.It has spherical structure with the size of low 10 nm and has abundant functional groups in surface.It exhibits non-toxic,harmless and has good fluorescence properties.The raw materials for synthesizing carbon dots are cheap and easy to obtain,and the synthesis methods are simple and numerous,especially the hydrothermal method is favored by researchers.So far,carbon dots have been widely used in bioimaging,sensing,catalysis and other fields.Although great research breakthroughs have been made,it was few been reported that the fluorescent aptasensor for food safety detection based on inner filter effect of AuNPs toward CDs.Therefore,the main contents of this study include preparation and characterization of carbon dots,as well as to construct a novel fluorescent aptasensor for the residual detection of pesticides and antibiotics using carbon dots as fluorescent signal and nucleic acid aptamers as a specific recognition molecule.The research mainly includes the following two parts:?1?A novel acetamiprid aptasensor based on the inner filter effect?IFE?of gold nanoparticles?AuNPs?toward fluorescent carbon dots?CDs?has been constructed.The sensor uses the fluorescent change value of CDs as the detection signal.In the absence of acetamiprid,the S-18 sequence can adsorb on the surface of AuNPs and enable their dispersion state even in the presence of high concentration of salt ions,which can effectively quench the fluorescence of the CDs.Upon adding acetamiprid pesticide,the aptamer sequence will firstly combine with it to form a target-aptamer complex.At this time,the unprotected AuNPs were exposed to high concentration of salt ions and were occur aggregated,which make the absorption spectra of AuNPs no longer overlapped with the fluorescence emission spectra of CDs,thus the solution system showed higher fluorescence phenomenon.Additionally,the effects of some vital parameters,such as the type and amount of AuNPs,on the fluorescent aptasensor were also investigated.Under optimal conditions,the proposed aptasensor has a detection limit as low as 1.08?g·L^-1 with a linear range of 5 to 100?g·L^-1 and shows high selectivity for acetamiprid over other control pesticides.Moreover,the aptasensor displays excellent accuracy and recovery in the detection of spiked real samples,The results show that the fluorescent aptasensor has application value in the field of food analysis and environmental detection.?2?On the basis of the above work,a new carbon dot was prepared to further improve the performance of aptasensor of the inner filter effect,and it was applied to the detection of antibiotic residues.The improved carbon dot has higher quenching efficiency?up to 65%?under the same concentration of quencher,which effectively solves the problem of sensitivity decline caused by higher fluorescence background in actual detection.Under the optimal conditions,the linear range of the proposed aptasensor is 0.04⁰.24?M,and the detection limit is as low as 0.018?M.At the same time,the method has high selectivity for other competitive antibiotics.Furthermore,the method has been applied to the determination of kanamycin in marked milk with a recovery of 90.0%to 98.3%.Therefore,it is an effective method for the rapid detection of kanamycin in milk and other animal-derived foods.In this study,aptamers are selected as target-specific recognition molecules.A novel fluorescent aptasensor for the detection of acetamiprid pesticides and kanamycin antibiotics residues in food based on the internal filtration effect of AuNPs toward carbon dots was established.The sensor established does not need to modify the CDs and aptamer,which make it has the advantages of high reliability,low detection cost and convenient operation.