| In recent years, food safety and health management has become a topicthat people pay close attention to. Among them, the indiscriminate use ofantibiotics in livestock breeding process has aroused special attention.Chloramphenicol abuse is also widespread, and the residues ofchloramphenicol in the food have serious side effects to the human body.Furthermore, the detection and control of microbes in food is anotherimportant aspect of food hygiene security. Salmonella, as one of the mostimportant pathogenic bacteria of foodborne diseases, should be under strictcontrol and management. Therefore, a simple, rapid and high sensitivedetection method for the above-mentioned materials is particularlyimportant. This research is divided into two parts: The first part is theconstruction of chloramphenicol electrochemical aptamer sensor and newstrategy for the detection of chloramphenicol; the second part is a novelcolorimetric assay for the invA gene of Salmonella detection. The concretecontent is as follows: 1. A simple and sensitive electrochemical aptasensor for determinationof Chloramphenicol in honey based on target-induced strand releaseChloramphenicol (CAP) is a broad-spectrum antibiotic that is widelyused in animals for the treatment of several infectious diseases because of itsexcellent antibacterial and well toleration. However, CAP has been found tohave serious side effects such as gray baby syndrome, leukemia, and aplasticanemia on human beings. For this reason many countries have banned theuse of CAP in food-producing animals. Combining the aptamer technologyand electrochemical sensing technology, we put the chloramphenicol astarget material and develop a novel electrochemical aptasensor for highlysensitive detection of Chloramphenicol (CAP) in honey based ontarget-induced strand release (TISR). CAP aptamer was immobilized onelectrode and then hybridized with the complementary biotinylated detectionprobe to form aptamer/DNA duplex. In the presence of CAP, the TISRresulted in the dissociation of biotinylated detection probe from the electrode.Then the binding of streptavidin-alkaline phosphatase (ST-AP) to theremaining biotinylated detection probe led to enzyme-amplifiedelectrochemical signal, which decreased with the increase of CAPconcentration. Under optimal conditions, the electrochemical signal waslinear with the logarithm of CAP concentrations in the range from1nM to1000nM with the detection limit of0.29nM of CAP. In addition, thedesigned strategy allowed the direct analysis of real honey samples and the results showed a good agreement with conventional LC-MS/MS method.2. A novel colorimetric assay for the invA gene of Salmonella detectionbased on DNAzyme self-assembled gold nanoparticlesSalmonella, belongs to enterobacteriaceae, is a gram-negative entericbacilli. It is one of the most important pathogens in foodborne diseases. Itspathogenicity mainly is closely related to the invasive protein, whichencoded by a series of genes, the invA gene as the main virulence factors.We built a colorimetric assay for the invA gene of Salmonella detectionbased on DNAzyme self-assembled gold nanoparticles. Amino-modifiedcapture probe was covalently immobilized on the surface of DNA–BINDplate, and further hybridized with target sequence and nanogold-DNAzymeprobe to form a sandwich-type hybridization structure. DNAzymes withperoxidase-like activity could catalyze TMB and H2O2which producedcolor change, and then quantitatively detect target sequence. Under optimalconditions, the absorbance value was linear with the logarithm of targetsequence concentrations in the range of0.5nM-50nM, with a limit ofdetection of0.44nM for target sequence. This method is simple, sensitive,which provides a new strategy for future practical salmonella detection, andprovides a powerful tool for the detection of pathogenic microorganisms inclinical diagnosis, food safety and environmental monitoring. |
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