Study Of Electrochemical Sensor For The Detection Of Antibiotics In Food Based On Molecularly Imprinted Technology And Chitosan

Antibiotics are products of microorganism metabolism, and they have the effect ofkilling or restraining the growth of microorganism. Antibiotics were used as drugs and havewidely applied in the treatment of bacterial infection or the inhibition of pathogenicmicroorganism infection. In recent years, the application of antibiotics in animal husbandryand agriculture was more and more widely, which increased the residual quantity ofantibiotics in food. Long-term ingestion of food containing excessive amounts of antibioticswill cause antibiotics accumulate in the body, human will be resistant to antibiotics, it isharmful to humans,health. The problem of antibiotic residues in food has increasinglysubjected to the attention of the international community, many countries have establishedmaximum residue limits of various antibiotics in food. However, the traditional methods forthe detection of antibiotics have many disadvantages. Therefore, it is necessary for us toexplore a sensitive and efficient method for the detection of antibiotics.In this work, five types of molecularly imprinted electrochemical sensors based onchitosan, nanomaterials and the specificity of molecularly imprinted polymers were fabricatedfor the detection of erythromycin, oxytetracycline, chlortetracycline, tetracycline andneomycin. These sensors all exhibited low detectin limits and wide liner range for thedetection of antibiotics, and they also have many good performance such as good repeatability,excellent stability and high selectivity. They have been used in the detection of antibiotics inreal samples, and got good recovery.The main contents of this work were shown in the following:1. A novel electrochemical sensor was fabricated based on gold electrode decorated bychitosan-platinum nanoparticles （CS-PtNPs） and graphene-gold nanoparticles （GR-AuNPs）nanocomposites for convenient and sensitive determination of erythromycin. The synergisticeffects of CS-PtNPs and GR-AuNPs nanocomposites improved the electrochemical responseand the sensitivity of the sensor. The molecularly imprinted polymers （MIPs） were preparedusing erythromycin and2-mercaptonicotinic acid （MNA） as template molecule and functionalmonomer, respectively. They were first assembled on the surface ofGR-AuNPs/CS-PtNPs/gold electrode by the formation of Au-S bonds and hydrogen-bonding interactions. Then the MIPs were formed by electropolymerization of HAuCl₄, MNA anderythromycin. The sensor was characterized by cyclic voltammetry （CV）, scanning electronmicroscope （SEM）, UV-visible （UV-vis） absorption speactra and amperometry. The linearrange of the sensor was from7.0×10^-8mol/L to9.0×10^-5mol/L, with the limit of detection（LOD） of2.3×10^-8mol/L （S/N=3）. The sensor showed high selectivity, excellent stability andgood reproducibility for the determination of erythromycin, and it was successfully applied tothe detection of erythromycin in real spiked samples.2. A molecularly imprinted electrochemical sensor was fabricated based on optimalchitosan-multiwalled carbon nanotubes composites （CS-MWCNTs） multilayer films and goldnanoparticles （AuNPs） for sensitive determination of oxytetracycline （OTC）. The optimalmultilayer of CS-MWCNTs composites and AuNPs were used for the augment of electronictransmission and sensitivity. The MIPs were synthesized using OTC as the template moleculeand o-phenylenediamine （OPD） as functional monomer. They were modified on goldelectrode by electropolymerization. The electrochemical imprinted sensor was characterizedby CV, SEM and amperometry. Under the optimized conditions, the sensor showed highselectivity, good repeatability and excellent stability towards OTC. The linear range was from3.0×10^-8to8.0×10^-5mol/L, and the LOD was2.7×10^-8mol/L （S/N=3）. The developed sensorshowed good recovery in real samples determination.3. A molecularly imprinted electrochemical sensor based on gold electrode decorated byβ-cyclodextrin-multiwalled carbon nanotube composites （CD-MWCNTs） and goldnanoparticles-polyamide amine dendrimer nanocomposites （Au-PAMAM） for selectivedetermination of chlortetracycline （CTC） was developed. The layer of MIPs was the outerlayer of the electrochemical sensor. In this article, CSDT acted as functional monomer, andCTC as the template molecule. CV and amperometry were used to characterize theelectrochemical behavior of the developed sensor. The linear range of the molecularlyimprinted sensor was from9.00×10^-8to5.00×10^-5mol/L, and the LOD was4.954×10^-8mol/L.The developed sensor showed high selectivity and excellent stability towards CTC. Theresults from real sample analysis confirmed the applicability of the sensor to quantitativeanalysis. 4. A electrochemical sensor for the determination of tetracycline （TC） was fabricatedbased on Fe3O4-multiwalled carbon nanotubes-SiO2-chitosan nanocomposites（Fe3O4-MWCNTs-SiO₂-CS）, Graphene-gold nanoparticles-chitosan nanocomposites（Gr-AuNPs-CS） and molecularly imprinted polymers. Fe3O4-MWCNTs-SiO2-CS andGr-AuNPs-CS composites have good electroconductivity and big specific surface area. TheMIPs were modified on gold electrode by electropolymerization and they were synthesizedusing TC as the template molecule and o-phenylenediamine （OPD） as functional monomer.The electrochemical behavior of the electrodes were characterized by CV and amperometry.The linear range was from5.00×10^-8to1.00×10^-4mol/L, the LOD was3.65×10^-8mol/L（S/N=3）. The sensor exhibited high selectivity and excellent stability towards TC. And it wassuccessfully applied to the detection of TC in milk and honey samples.5. A novel neomycin imprinted sensor was developed based on chitosan-silivernanoparticles （CS-SNP）, graphene-multiwalled carbon nanotubes （GR-MWCNTs） compositesand the specifity of molecularly imprinted polymers. MIPs were synthesized byelectropolymerization using neomycin as the template, and pyrrole as the monomer. Thecharacterization of imprinted sensor has been carried out by scanning electron microscope（SEM） and Fourier transform infrared spectroscopy （FTIR）. The performance of the proposedimprinted sensor has been investigated using CV and amperometry. A number of factorsaffecting the activity of the imprinted sensor have been discussed and optimized. Under theoptimized conditions, the linear range of the sensor was from9×10^-9mol/L to7×10^-6mol/L,and the LOD was7.63×10^-9mol/L （S/N=3）. The film exhibited high binding affinity andselectivity towards the template neomycin. Furthermore, the proposed sensor was applied todetermine the neomycin in milk and honey samples, and the good recovery implied itsfeasibility for practical application.