Construction Of Label-free Molecularly Imprinted Polymer-based Electrochemical Sensor For Detection Of Sulfonamide Antibiotics

Sulfonamides(SAs)are a class of broad-spectrum synthetic antibacterial and antiinflammatory antibiotics that are widely used for the prevention and treatment of human and animal infections as well as the growth promotion in animal husbandry due to their high efficacy and low cost.However,the excessive use of SAs has led to SAs residue contamination of various organisms,and the natural environment.Therefore,it becomes important to develop a rapid,sensitive and efficient way to detect SAs.Electrochemical sensing technology is widely used for the detection of antibiotics because of its high sensitivity,fast response,small size,portability,low cost,low reagent content,and ease of operation.Molecularly imprinted polymers,known as "bionic antibodies," offer the opportunity to detect antibiotics in an efficient,sensitive,and cost-effective manner due to their simplicity of preparation,physical and chemical stability,low cost,and high selectivity.Currently,molecularly imprinted electrochemical sensors are widely used for the detection of small molecules,drugs,and food-borne pathogenic bacteria.In this thesis,sulfamethizole and sulfadiazine were selected as template molecules for a progressive study in two directions,from simple single-template imprinting to complex double-template imprinting,and from direct detection of electrochemical signals to amplification of electrochemical signals.The best functional monomer was selected by quantum chemical calculations combined with experiments.Functional monomers are copolymerized with templates on the surface of a glassy carbon electrode(GCE)to form a molecularly imprinted polymer with a recognition target template,which is used as a recognition element to capture the target antibiotic.The final quantitative and qualitative analysis of the target antibiotics was performed by means of electrical signals.In addition,the main work as follows:Suitable polymers were selected as the best functional monomers before the experiments,and the imprinting factors of four 3-substituted thiophenes(3-thiophene ethanol,3-thiophene methylamine,3-thiophene acetic acid,and 3-thiophene boronic acid)as functional monomers and the strength of recognition signals were verified by quantum chemical calculations and experiments.The best functional monomer,3-thiopheneethanol,was selected.3-thiopheneethanol and sulfamethizole were copolymerized on the GCE surface by one-step electropolymerization.Then the template molecule was completely removed using CTAB/HAc as the eluent,resulting in a molecularly imprinted sensor with specific recognition capability.After verifying the experimental feasibility,a series of experimental conditions,such as the preparation of molecularly imprinted polymeric membranes and the recognition response,were optimized in order to obtain the best sensor.A molecularly imprinted electrochemical sensor based on sulfamethizole detection was prepared under optimal conditions.The imprinted sensor was able to remove the template quickly(20 min)and identify the target molecule(30 min).With a low detection limit and a wide linear range,there is a linear correlation between the relative value of the impedance response ΔR/R and the logarithm of the concentration within this linear range,with a calibration curve of ΔR/R = 1.27 lg C+ 5.23 and a correlation coefficient of 0.999.The sensing has good repeatability,reproducibility and storage stability.Finally,the spiked recovery method was used to verify the application of the sensor in real samples,and the prepared imprinted sensor could be applied to lake water and milk.The final total results showed a recovery of 91.69%～ 108.32%.To further investigate the ability of nanomaterials to improve sensing performance and the recognition and detection of dual-template imprinted polymers,We selected sulfamethoxazole and sulfadiazine as template molecules and 3-thiopheneethanol as a functional monomer to construct a dual-template molecularly imprinted electrochemical sensor by cyclic voltammetry copolymerization on GCE modified with carbon nanotubes and nanogold,after CTAB/HAc removal of the dual templates.A series of optimized conditions were used to prepare a dual-template molecular blotting sensor with a large number of recognition sites that was fast,sensitive,specific,and label-free.The sensor can remove the template(45 min)and capture the template molecules(45 min)in a relatively short time.With a low detection limit and a wide linear range,there is a linear correlation between the relative value of the impedance response ΔR/R and the logarithm of the concentration within this linear range.In addition,this dual-template imprinted electrochemical sensor has excellent specificity,parallelism,and regenerative properties.In addition,the dual-template imprinted electrochemical sensor has excellent specificity,parallelism,and regenerative properties.The sensor can recognize sulfamethoxazole and sulfadiazine in two other structurally similar antibiotics and is capable of repeatedly removing and capturing template molecules more than 5 times.