Quantum Dots-molecular Imprinting Fluorescence Sensing For Detection Of Tyramine And Heterocyclic Amines In Food

Nowadays,sensors based on fluorescent-molecularly imprinted polymers have been widely used in many fields,and researches on food analysis and detection are not uncommon.These sensors combine the high sensitivity of fluorescent with the high selectivity of molecularly imprinted polymers.Compared to traditional large-scale instruments,it simplifies sample preparation steps,reduces analysis response time,and efficiently detects trace analytes in complex food substrates.In this study,two kinds of molecular imprinting-based fluorescence sensors were constructed for the detection of the tyramine and heterocyclic amines in foods.First of all,by using the characteristics of high fluorescence stability and strong photobleaching resistance of carbon dots,it is used as a fluorescent material.A carbon dots-molecularly imprinted fluorescence sensing test strip was constructed to detect tyramine in food.The sol-gel method was used to polymerize the carbon dots-molecularly imprinted polymers in situ on the surface of the filter paper strips grafted with double bonds.Through the electron transfer between tyramine and carbon dots,the fluorescence of the carbon dots is quenched,thereby achieving the purpose of detection.The reaction conditions were optimized and the morphologic structures of test strip were characterized by scanning electron microscopy.In addition,the adsorption performance and selectivity of the test strips were evaluated by equilibrium adsorption experiments,adsorption kinetic experiments,adsorption selectivity experiments and adsorption competition experiments.Finally,the relative fluorescence intensity of the test strips decreased in a linear correlation with the concentration of tyramine from 0.5 to 10.0 mg L-1 with the detection limit of 0.059 mg L-1(S/N=3);for spiked levels of tyramine of 1,5 and 7.5 mg L-1,the recoveries of rice vinegar and white rice vinegar are 90.9-104.4%,and the RSD is<5.8%.Secondly,for the purpose of determining aminoimidazole nitrogen heterocyclic amines(AIAs)which are trace amounts in food,and having mutagenic activity and potential carcinogenicity,a CdSe/ZnS quantum dots-molecularly imprinted fluorescence sensing material with high selectivity and sensitivity was constructed.In the experiment,2-aminobenzimidazole was as a simulant template which has a similar molecular structure of AIAs,CdSe/ZnS quantum dots was as the fluorescent luminescent core,and the molecularly imprinted polymers were synthesized on the surface of quantum dots by sol-gel method.The synthesis conditions of the materials were optimized and the successfully synthesis of the materials was confirmed by using FTIR spectrum and scanning electron microscopy.The equilibrium adsorption and binding properties,adsorption kinetics and adsorption selectivity of the materials were determined.Eventually,the fluorescence sensing material for the determination of AIAs was established.The linear range of CdSe/ZnS@MIP as a fluorescent sensing material for heterocyclic amines is 0.5-20.0 μg L-1,the detection limit is 0.25 μg L-1(S/N=3),and to test the repeatability of the materials,the RSD of the five-time heterocyclic amines were determined to be 2.41%;the proposed method was further applied to determine heterocyclic amines in dried beef floss and grilled fish samples with satisfactory recoveries(82.8-110.8%),and the RSD is<5.5%.In summary,a simple,rapid and low-cost carbon dots-molecular imprinting test strip was prepared for the detection of tyramine in food.In addition,a sensitive and effective CdSe/ZnS quantum dots-molecularly imprinted fluorescent sensing material with good accuracy,stability,high reproducibility,high selectivity and sensitivity for the detection of amino-imidazole nitrogen heterocyclic amines was prepared.