Developmentoffluorescentquantumdotbased New Methods For Trace Residues Detections

With the applications of fluorescent semiconductor nanocrystals (also known as quantum dots) in various analytical fields as the background, this dissertation deals with the issues of developing series ultrasensitive, high-throughput and rapid detection methos using quantum dots as the fluorescent labeling probes for food safety detections.Firstly, bovine serum albumin (BSA) was used to modify and coat the synthesized quantum dots (QDs), which protected the surface of the QDs and enhanced the fluorescent properties of the QDs. Then the BSA coated QDs were used to label the antibody against target analyte. Following, the fluorescent labeled antibody was used in the microfluidic chip to detect the target analyte under the competitive immunoassay model. In the microfluidic chip, the fluorescent labeled antibody-coating antigen complex and fluorescent labeled antibody-antigen were separated from each other by the electric field and the fluorescent signals were recorded by the laser induced fluorescence (LIF) detector. The calibration curve was developed based on the readout signals of the fluorescent labeled antibody. The development of the method for clonazepam was successfully achieved by the detection of spiked samples.Secondly, the biotin modified denatured BSA (biotin-dBSA) was used to coat the QDs, which also induced the fluorescence enhancement and surface stability of QDs. Afterwards, the fluorescent aggregates were prepared by the biotin-dBSA under the effect of biotin-avidin recognition. The fluorescence property was further improved by the form of aggregates. The QDs based fluorescent aggregates were used to detect target protein in the traditional Western Blot. The fluorescent aggregates were used to recognize the second antibody on the film, realizing the ultrasensitive detection of target protein successfully.Thirdly, the novel MQCA detection method was constructed by the sequential injection system and magnetic and gold nanoparticles probes. The RT-PCR was adopted for the quantitative detection of the single-stranded DNA probes, which was related to the concentration of the target MQCA. The ultrasensitive detection of MQCA was achieved with the limit of detection of 1.4 aM, which could meet the requirement of the official detections. Meanwhile, fluorescent quantum dots were used in the PCR system to optimize the non-specific amplification. The added concentration of QDs was optimized and the inhibition effect to the non-specific amplification was achieved successfully. At suitable concentration, the inhibition effects under different anneal temperatures and various amplified template length were also studied at length. Results indicated that QDs could realize the perfect inhibition of non-specific amplification of PCR under all above mentioned conditions. Furthermore, the possible theoretical inhibition mechanisms were explained from three aspects, which gave the useful theoretical support for the practical application of QDs in PCR optimizations.Lastly, the research of quantum dots based fluorescent encoded microspheres was explored. The microfluidic system based preparation method for microsphere was developed successfully and the related parameters, which influence the morphology and size of the microspheres, were optimized. The synthesized microspheres were characterized by microscopy, SEM and so on. Importantly, the fluorescent signal of the encoded microspheres was decoded through the software successfully. The fabricated microspheres have the potential to be the useful probes in the development of highthrough put methodology.