Simultaneous And Rapid Detection Of Multiplex Antibiotic Residues In Milk With Multicolor Quantum Dots Based On Fluorescence Immunoassay

The continuous development of the nanotechnology provided a broad road for the research and application of nanomaterials in fields of mechanics, magnetics, electricity, thermotics, optics, and so on. For their researches and applications in optics, semiconductor nanomaterials fluorescent quantum dots (QDs) have attracted researchers’great concerns, with their capabilities of bio-marking, tracing and imaging. As a novel kind of fluorescent nanomaterials, QDs have been widely used in biological imaging, disease diagnosis, environmental monitoring, and drug residues detection, because of their excellent fluorescence properties compared with traditional fluorescent dyes. Among them, QDs-basedcnce immunoassay has been extensively used for the detection of small molecules. The exposure of various food safety incidents in recent years aroused people to rethink the issue of food safety monitoring, such as drug residues and illegal additive. Among various drug residues in animal food, antibiotics residues are important monitoring objects in quality control of food, due to their importance and universality in clinical application.In animal food, milk is very important in people’s daily life and antibiotic residues in them will directly affect people’s health, so it is essential to develop new methods, which could realize accurate, sensitive, rapid, and convenient detection of antibiotic residues in milk. The combination of QDs and immunoassay may provide opportunities for the establishment of new methods. This thesis reports the works as the following:(1) The quantum dots with fluorescence emission wavelength of520nm,565nm and610nm were chose, and they were respectively used to label antibodies of three antibiotics through covalent bond, then three different quantum dots-antibody probes were got (OD520-anti-streptomycin antibody, QD565-anti-tetracycline antibody and QD610-anti-penicillin G antibody). The stability and specificity of the probes were investigated.(2) Directly competitive fluorescence immunoassay (cFIA) based on quantum dots-antibody probes was established, and the optimum analysis conditions were investigated. Then based on array analysis mode, three antibiotics (streptomycin, tetracycline and penicillin G) had been detected simultaneously, sensitively and visually in ELISA plate. The linear range of the method for streptomycin and tetracycline was from0.01ng/mL to25ng/mL, and0.01ng/mL to10ng/mL for penicillin G. The limit of detection for them was all0.005ng/mL. Compared with the results of the commercial enzyme-linked immunosorbent assay (ELISA) kit for the three antibiotics, this method had a higher accuracy and sensitivity for the analysis of the three antibiotics in actual milk samples.(3) The antigens for three antibiotics were fixed in the same well on ELISA plate at the same time. Then cFIA was introduced based on quantum dots-antibody probes and then-fluorescence characteristic of "simultaneous multiple emission with the same excitation", and residues of streptomycin, tetracycline and penicillin G were detected in the same milk sample simultaneously. Compared with the array analysis mode above, this method is not only accurate, sensitive and efficient, but also timesaving, convenient and economic.