Detection Method Research Of Food-borne Pathogenic Bacteria Using Quantum Dots-nanogold Composite Probe

Food safety incidents caused by food-borne pathogenic bacteria,has become an important public health problem worldwide.However the existing detection technologies have some defects,can't satisfy the detection requirements for rapidness and sensitivity,so the development of a new type rapid detection technology becomes very meaningful.Along with the development of nanotechnology research in recent years,the studies also constantly focus on the using of nanometer materials to detect the food-borne pathogenic bacteria.The cadmium telluride(Cd Te)has excellent luminescent properties,and the preparation of composite probes with gold nanoparticles can enhance the luminescence signal.At present,there are few reports on the detection of food-borne pathogenic bacteria based on the principle of signal amplification by quantum dots-nanogold composite probes.Therefore,we prepared the cadmium telluride quantum dots through the water phase synthesis method.We used an functional objective specific DNA sequences,in order to let hundreds of quantum dots connect to a gold nanoparticle,which could prepare probe for signal amplification;In addition,because Fe3O4 magnetic nanoparticles have a good magnetic separation effect,magnetic nanomaterials can be used for separation and capture,which can avoid the pre-bacteriosis process of plate method and the amplification process of molecular biological methods,which is convenient and quick,saves time and labor.Then we prepared amination Fe3O4 magnetic nanoparticles through water hot-solvent hot method,and used the principle of avidin biotin specific binding to connect another target bacteria capture specific sequences of DNA probe.Then we added the DNA sequence of target bacteria,to measure bacteria DNA fluorescence intensity on the F-7000 fluorescence spectrometer.On the optimized experimental conditions,the measured fluorescence intensity and Salmonella DNA concentration had a linear relationship within the scope of 10 ~ 1000 fmol/L,the regression equation was IF = 0.198 [DNA](fmol/L)+ 55.00,R2 = 0.997,the detection limit was 8 fmol/L.Ten times repeated detection of 1000 fmol / L Salmonella DNA concentration,the relative standard deviation(RSD)is 3.8%.In the detection of Salmonella contamination milk samples,the results also showed good accuracy of this method,and the detection limit was 4 fmol/L.In the detection of Staphylococcus aureus,the fluorescence intensity and concentration of Staphylococcus aureus DNA had good linear relationship within the 1 ~ 1000 fmol/L,the regression equation was IF =5.824[DNA](fmol/L)+ 1575,R2 = 0.996,the detection limit was 11 fmol/L.Ten times repeated detection of 1000 fmol / L Staphylococcus aureus DNA concentration,the relative standard deviation(RSD)is 0.81%.Staphylococcus aureus colony number and fluorescence intensity showed a good linear relationship within the scope of 26-652 cfu/m L,and the regression equation was IF = 8.005(cfu)(cfu/m L)+ 1964,R2 = 0.996,the detection limit was 14 cfu/m L.For the detection of Staphylococcus aureus contamination in milk samples,we calculated the colony number according to the fluorescence intensity using the above equation.Then we compared the calculated results with the results of the plate count method,the recoveries were between 89.78% and 100.83%,which showed good accuracy.Therefore,these research results showed that the quantum dots-nanogold composite probe,combining with the magnetic separation of magnetic nanoparticles,for the detection of Salmonella and Staphylococcus aureus,had fast,low cost,super sensitive and accurate features,which provided a new method in order to overcome the limitations of existing detection technologies of food-borne pathogenic bacteria,and had good application prospect.