Development Of Quantum Dots Fluorescence Kit For Cadmium Ions And Application In Food Detection

Developing a new type of quantitative detection of heavy metal cadmium content is based on protein materials and platform conditions,which is provided by the laboratory of Vazyme Biotech Co.,Ltd.The test method use quantum dots instead of the traditional tracer material.As the tracer material,the quantum dots will not quench easily,which has the advantages of excellent stability and high sensitivity.The paper expounds that preparingthe CdSe/CdS/ZnS quantum dots,then debugging package concentration of the control line and test line,and regulating the dilution ratio of the quantum dots.Moreover,the content of the protein or sucrose in the quantum dot diluent and the sample pad treatment liquid or sucrose were adjusted.The performance of the reagents was evaluated,including sensitivity,specificity,precision and stability.1 The quantum dots wavelength is at 605 nm.2 Preparing and screening the monoclonal antibody,then we detected the titer of monoclonal antibody 6C3 and 8E8,which are up to 1.28×105 and 1.024×106.3 Debugging the optimal package concentration of the control line and test line in the checkerboard titration.The optimal package concentration of the control line was set as 0.5 mg/mL,0.75 mg/mL,1.0 mg/mL;the optimal package concentration of the test line was set as 0.5 mg/mL,1.0 mg/mL,1.5 mg/mL.Finally,the optimal concentration of the control line and the test line was determined to be 0.75 mg/mL and 1 mg/mL.In accordance with the optimal package concentration of the test line and the control line,the dilution ratio between quantum dots and diluent was set as 1:1,1:4,1:9(volume ratio).In addition to the dilution ratio,the other components of the control experiment were same.Then we compared the difference between the linear range and the measured value under different quantum dots.Finally,the dilution ratio was determined to be 1:4.Different amounts of sucrose were added in the quantum dots dilution buffer:0,2%,5%,10%,while diluting quantum dots in the best proportion.In the control experiment,the other components were same except for the quantum dots.Compared the difference between the linear range and the measured value under different filter condition.Finally,the amounts of sucrose were added in the quantum dots dilution buffer,which was determined to be 5%.Different concentrations of BSA were added to the quantum dots dilution buffer:0,0.1%,0.5%,2%,while according to the optimal package concentration of the test line and the control line.In the control experiment,except for the quantum dots,the other components were same.Testing the mixture of chelates salt,and then compared the difference of results and the running plate under different filter condition.Finally,the amounts of BSA were added in the quantum dots dilution buffer,which was determined to be 0.5%.Different concentrations of casein and sucrose were added to treatment solution for the glass fibre(0.1mol/L HEPES 8.0),while according to the optimal package concentration of the test line and the control line.In the control experiment,the other components were same except for the glass fibre.Testing the same sample,and then compared the difference of results and the running plate under different filter condition.Finally,the concentrations of casein and sucrose were determined to be 0.5%and 5%.The sensitivity of kit is up to 1.25 ng/mL.The linear range of kit is 1.25-500 ng/mL.Detecting the different chelate of metal ions with EDTA,the results showed that the kit had no cross reaction with the metal ion,like Cu2+、Mn2+、Hg2+、Zn2+、Fe3+、Pb2+、Cr3+Detecting the Cd2+-EDTA standard solution with concentrations of 2.5 ng/mL and 100ng/mL,repeating 10 times,respectively.Then calculating the value of coefficient of variation,which were both less than 15%.The reagent cards were placed at 37℃,and assessed the accelerated stability for 20 days.Compared with 4℃,when detecting the high and the low values,the deviation of results were less than 15%.The recovery rate of Cd2+ in rice is 96.1%,which belongs to 85%-115%.The result which is detected by kit is accurate and reliable.