Preparation Of Dendrimer Gadolinium Probe And Its Detection Of Salmonella In Dairy Products

Foodborne pathogenic bacteria lead to frequent food safety incidents,and Salmonella infection ranks first in the outbreaks of food-borne bacteria.Rapid and sensitive detection technology is the key to preventing the outbreak of foodborne diseases.However,current detection technologies such as traditional microbial culture methods,surface plasmon resonance,and immunoassays cannot meet the needs of rapid and efficient detection.In order to solve the problem of detection technology and better ensure food safety,this studied the preparation process of polyamidoamine dendrimer gadolinium specific probe and used it for the rapid detection of Salmonella in dairy products.Using paramagnetic nano-metal particle Gd³⁺as the magnetic signal material,a novel nano-macromolecular material dendrimer polyamido-amine(PAMAM)with high branched,high symmetric and high functional group density was used as the probe scaffold.At the same time,a signal amplification system of Streptavidin-Biotin was introduced.The antibody and the magnetic complex were combined by the streptavidin-biotin system to obtain an immune probe.Immunoprobes capture Salmonella through antigen-antibody interactions and then separate them from the mixture through membrane filtration.Finally,nuclear magnetic resonance is used to detect the changes in the longitudinal relaxation signal of the filtrate to achieve the detection of the target bacteria.The main research contents are as follows:1.Design and preparation of probe with high relaxation effect.The immune probe was synthesized by dendrimer polyamide-amine(PAMAM),a novel nanomolecular material with high branching,symmetry and functional group density,and the main synthesis conditions were optimized.The results showed that the optimal synthesis conditions of Biotin-PAMAM were the molar ratio of 1:5 and the reaction at 25?for 2 h.The optimum synthesis conditions of PAMAM-DTPA were as follows:the mole ratio of DTPA to PAMAM was 40:1,the synthesis temperature was 37?,the buffer system p H was 9,and the reaction time was 3 h.In order to verify whether the effect of the probe on the longitudinal relaxation time of water protons was enhanced after the introduction of PAMAM material,the longitudinal relaxation time T₁value of Biotin-PAMA-DTPA-Gd and DTPA-Gd were measured respectively.The results showed that the longitudinal relaxation rate of Biotin-PAMAM-DTPA-Gd was about 2.3 times of that of DTPA-Gd after the introduction of PAMAM,which indicated that the introduction of PAMAM could enhance the interaction between the probe and water particles and improve the relaxation rate of the probe.2.Construct a detection system for Salmonella.In order to realize the specificity and rapid detection of the target bacteria,the main parts of the detection system,such as the amount of SA,the amount of biotinylated antibody,the amount of Biotin-PAMAM-DTPA-Gd complex and the capture time of the target bacteria were optimized respectively.The results showed that the signal output of the probe was stable under the conditions of 4?L SA dosage,molar ratio of biotinylated antibody dosage of 1:5,100?L Biotin-PAMAM-DTPA-Gd complex dosage and 50min capture time of the probe,which was more conducive to capture the target bacteria.3.Application of detection system in milk.In order to ensure the actual detection effect of the probe,the specificity,anti-interference ability,detection sensitivity and detection effect of the probe in milk were evaluated.The results showed that the probe could specifically capture Salmonella in the presence of interfering bacteria,and 10³CFU/m L of Salmonella could be detected in both PBS solution and milk.