| Chloramphenicol is a broad-spectrum antibiotic,which can inhibit a variety of gram-positive and Gram-negative bacteria.Meanwhile,chloramphenicol has low cost and high economic benefit,so it is widely used in animal husbandry and aquaculture industry.But chloramphenicol,which is used in large quantities,can enter the human body along the food chain and cause serious harm.Therefore,the detection of chloramphenicol in animal-derived foods（such as milk）is of great significance.At present,although the traditional chloramphenicol detection methods have high sensitivity and stability,most of them have shortcomings such as complex analytical steps,expensive instruments and equipment,high instrument maintenance costs,complex sample pretreatment and the need for professional personnel to operate.Therefore,it is of great practical significance to develop a simple,sensitive and reliable method for rapid detection of chloramphenicol residues.In order to build a sensor with high sensitivity,fast detection speed and reliable detection results for the rapid detection of chloramphenicol residues,the molecularly imprinted electrochemical sensor with three different modes,namely,single signal single recognition element,double signal single recognition element and single signal double recognition element,was constructed by combining molecularly imprinted technology with electrochemical technology.The main contents are as follows:（1）Preparation and performance study of molecularly imprinted electrochemical sensor based on chitosan-multi-walled carbon nanotubes nanocomposites.We successively modified the surface of glassy carbon electrode with CS-MWCNTs（Chitosan-Multi-walled carbon nanotubes）nanocomposites and molecularly imprinted polymers.Among them,CS-MWCNTs nanocomposites with excellent conductivity were used as sensitizing materials to enhance the sensitivity of the sensor to reduce the influence on the sensitivity of the sensor due to the poor conductivity of the molecularly imprinted polymer.Molecularly imprinted polymers were synthesized by electrochemical polymerization,using chloramphenicol as template molecule and o-phenylenediamine as functional monomer.After elution to remove the template molecule,molecularly imprinted polymers that specifically recognized the chloramphenicol molecule were obtained.By optimizing the conditions that might affect the experimental results one by one,under the optimal conditions,the linear detection range of the sensor was 1.0×10-7 g/L～1.0×10-3 g/L,the detection limit was 3.3×10-8 g/L.The recovery rate of standard addition in milk was between 97.40%～103.60%,and the Relative Standard Deviation（RSD）was between 1.55%～3.94%.（2）Preparation and performance study of novel dual-signal Si O2-COOH@MIPs electrochemical sensors based on Ni Fe-PBA and SnS2 nanoflowers.We modified the prepared Ni Fe-PBA,SnS2 nanoflowers and Si O2-COOH@MIPs on the surface of the glassy carbon electrode sequentially.The function of Ni Fe-PBA was to provide the second detection signal.SnS2 nanoflowers could promote the oxidation of nickel ions in Ni Fe-PBA and further amplify the second detection signal.At the same time,the three-dimensional flower-like structure of SnS2 nanoflowers could also increase the specific surface area of the electrode and provide more attachment sites for the next step of material modification.Using the carrier method of surface molecular imprinting technology,using carboxylated Si O2nanospheres as the carrier,chloramphenicol as the template molecule,methacrylic acid as the functional monomer,ethylene glycol dimethyl acrylic acid as the crosslinking agent,azodiisobutyronitrile as the initiator,a new Si O2-COOH@MIPs that could specifically recognize chloramphenicol was synthesized by thermal polymerization.The sensor with double signal synergy had higher sensitivity than the single signal sensor.At the same time,a recognition element with the ability to recognize chloramphenicol was synthesized outside the electrode by the carrier method,which saved the time of electropolymerization and elution compared with most other sensors using electropolymerization methods to prepare molecularly imprinted polymers,and was more in line with the requirements of rapid detection.Under the optimal detection conditions,the linear detection range of the sensor was 1.0×10-8 g/L～1.0×10-2 g/L,and the detection limit was 3.3×10-9 g/L.The recovery rate of standard addition in the actual sample detection of milk was 97.70%～104.10%,and the RSD was between 2.19%～4.68%.（3）Preparation and performance study of molecularly imprinted aptamer electrochemical sensor based on Au NPs/CS-MWCNTs nanocomposites and dual recognition strategy.We successively modified the surface of glassy carbon electrode with CS-MWCNTs nanocomposites,Au NPs,aptamers and molecularly imprinted polymers.Among them,CS-MWCNTs nanocomposites with excellent conductivity were used to enhance the sensitivity of the sensor.The Au NPs obtained by electrodeposition could not only further improve the sensitivity of the sensor,but also formed gold-sulfur bonds with the aptamer modified with sulfhydryl groups to achieve the purpose of fixing the aptamer.Molecularly imprinted polymers were obtained by electrochemical polymerization with dopamine as functional monomers and aptamers and chloramphenicol complexes as template molecules.When the aptamer and molecularly imprinted polymer were combined,a new type of hybrid recognition element was formed.Compared with the single two recognition elements,the hybrid recognition element had high sensitivity,high specificity and high stability under harsh environmental conditions.By optimizing the experimental parameters such as complexation time,scanning period and scanning rate,the linear detection range of the sensor was 1.0×10-8 g/L～1.0×10-2 g/L,and the detection limit was 3.3×10-9 g/L.The recovery rate of standard addition in the actual sample detection of milk was97.90%～107.90%,and the RSD was between 1.09%～3.73%.Three novel molecule-imprinted electrochemical sensors for the detection of chloramphenicol constructed in this paper could all achieve high sensitivity detection of chloramphenicol residues in actual milk samples after analysis and testing.Compared with the single signal sensor,the dual signal synergistic sensor had higher sensitivity.Compared with single recognition element,hybrid recognition element had high sensitivity,high specificity and high stability under harsh environmental conditions.The three molecularly imprinted electrochemical sensors constructed in this paper are of great significance for promoting rapid detection of antibiotic residues and ensuring food quality and safety.At the same time,it lays a foundation for the further development of antibiotic residue detection equipment. |
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