Study On The SERS Detection Of Oxytetracycline And Application Based On The Self-assembled Gold And Silver Nanoparticles

As a kind of tetracycline,oxytetracycline?OTC?belongs to broad-spectrum antibiotics and it can inhibit both Gram-positive bacteria and Gram-negative bacteria.At present,OTC is widely used in pharmacy making and animal breeding,but the unconscionable addtion and the incomplete treatment have made OTC residues becoming a focused issue for human beings.Antibiotics enter into human body through the food with antibiotic residues and cause damage to human body.In addition,the antibiotic residues in environment have made probiotics like lactobacillus plantarum generating antibiotics resistance and these probiotics transmit the resistance genes to other pathogenic bacterias in human body,it also makes a great threat to human health.At present,about the detection of antibiotic residues in food,there are many disadvantages such as high requirement for sample treatment,complex operations of instruments,expensive and long time for detection.On microbial screening of resistant strains,there are also problems like time-consuming and easy to generate deviation.This reserach has used the Surface Enhanced Raman Scattering?SERS?combined with those nano materials which have good SERS enhancement effect to create new method for detecting OTC residues in milk and study the influence that OTC has on lactobacillus plantarum.Specific reserach is as follows:Firstly,a new method of detection for OTC based on self-assembled SERS-active silver nanostructure was constructed.This method has assembled the Ag nanorods?AgNRs?and Ag nanoparticles?AgNPs?with the stem-loop DNA containing the OTC aptamer sequence.With the presence of OTC,it was captured by aptamers and then the aptamer structure was destroyed,making the distance between AgNRs and AgNPs shorten and enhancing the Raman signal of the Raman molecules?4-MBA?modified on the AgNPs meanwhile.Under optimal detection condition,the Raman intensity and the concentration of OTC had a good liner relationship?y=4660.35+2139.42x,R²=0.9984?in the range of 4.96×10^-2 fg/mL-4.96×10²fg/m L and the detection limit was as low as 0.0373 fg/m L.This method was proved can be used for rapid detection of practical samples through the specificity analysis and the recovery experiment.Secondly,a new method of detection for OTC based on self-assembled SERS-active gold and silver nanostructure was contructed.Based on the first method,this method was improved in the aspect of nano materials in which hollow gold nanoparticles were synthesised according to the replacement reaction between HAuCl₄ and Ag based on the AgNPs.Under the same model,this method has improved the detection sensitivity.Under optimal detection condition,the Raman intensity and the concentration of OTC had a good liner relationship with the equation y=1136.31+227.7x?R²=0.9954?in the range of 4.96×10^-3 fg/m L-4.96×10² fg/mL and the detection limit was 0.00012 fg/m L.It also had a good result in the experiment for specificity and recovery rate and it can be used for rapid detection for practical samples.At last,the influence on the lactobacillus plantarum that OTC has was preliminarily explored with the solid SERS subtrate based on the AgNRs.A good SERS substrate was made through assembling AgNRs with quartz chip and was used to detect the SERS signal of bacterial cells which were incubated with different concentrations of OTC at the time of 30min,60 min and 90 min.It can provide the information of compositional variation of bacterial cells through analyzing the position and intensity change of the Rman peaks under the condition of different concentration of OTC and different time.Also,it has a good benefit to know better about the influence of antibiotics on microorganism.This study has provided a good fundation for the research on the rapid screening of antibiotic resistant strains.