Study On Fluorescence Immunoassay Based On Upconversion Nanoparticles As Labels And Magnetic Separation For The Detection Of Tetracycline

In this work,upconversion fluorescent nanomaterials were used as the marker and magnetic microspheres were used as the separation carrier,an ultrasensitive fluorescence immunoassay based on the principle of immune competition has been established for the detection of tetracycline in animal-derived foods.The OA-UCNPs were synthesized by hydrothermal method.Ligand exchange method was used to replace hydrophobic groups with hydrophilic groups on the surface of OA-UCNPs,and in this way we could get the water-soluble upconversion nanomaterials(PAA-UCNPs).The PAA-UCNPs were combined with tetracycline antibody to prepare the fluorescent signal probe by activation ester method,and the MPMs and tetracycline antigen were coupled to prepare the immune capture probe similarly.After optimization of experimental conditions,the addition amount of capture probe and signal probe was 50 μL respectively and the incubation time was 30 min.This method could detect the total amount of tetracycline,oxytetracycline,chlortetracycline and other tetracycline antibiotics,no cross-reactions with other common veterinary drugs were observed.The LOD of this method was 0.005 pg mL-1 and the LOQ was 0.01 pg mL-1.Samples extracting solution could be directly tested after 10-fold dilution,and the recoveries ranged from 85.92%to 109.96%,CV%ranged from 4.69%to 16.01%.At the same time,the accuracy of the method was verified by LC-MS/MS and ELISA test kit at the spiked level of 10,50,100 μg kg-1.Compared with LC-MS/MS and ELISA test kit,the proposed method had simpler test process and higher sensitivity.In addition,the trace amount of tetracycline in the positive samples of carp and grass carp was detected by our assay,but LC-MS/MS and ELISA test kit were unable to detect the trace amount of tetracycline because of their limited test sensitivity.In this study,we had established an ultrasensitive fluorescent immunoassay to detect tetracycline antibiotics with upconversion nanomaterials as labels and magnetic separation.This method was high sensitivity,easy operation,convenient and time-saving,it is suitable for rapid quantitative detection of trace tetracycline antibiotics residues in animal-derived foods.