Preparation Of New Sensor Based On Mesoporous Materials And Detection Of Harmful Substances In Milk

As a high-nutrition food,milk can supplement a variety of nutrients needed by the human body,and is gradually sought after by people.In recent years,the processing technology of milk has been continuously improved,which has caused concern about the safety of milk.Antibiotics are widely used in animal husbandry.Excessive use of antibiotics will cause antibiotic residues in milk,and it is also susceptible to pathogenic bacteria during milk processing and storage.However,the current detection methods are cumbersome and time-consuming,so a fast and simple detection method needs to be developed.Electrochemical sensor detection technology is a new type of detection method.It has the advantages of simple operation,fast and sensitive detection,low price,and stable performance.It is widely used in the detection of harmful substances in food.Based on this,three electrochemical biosensors were designed for the detection of Staphylococcus aureus?S.aureus?and penicillin sodium?Pen G?.Compared with traditional detection methods,the detection results were not significantly different,this indicates that the sensor can be used to detect S.aureus and Pen G in actual milk samples.1 Preparation of electrochemical immunosensor based on mesoporous SiO₂ and detection of S.aureusAn antibody?Ab?-hierarchical mesoporous silica?HMS?bioconjugate was used to design a sensitive electrochemical immunosensor for label-free detection of S.aureus at low concentrations.First,HMS was prepared using a biological template method with butterfly wings.The results show that HMS not only accurately replicates the shape of butterfly wings but also has a multi-stage pore structure.Then,the carrier material was amino-functionalized and Ab was supported with glutaraldehyde as a cross-linking agent,and then the Ab-HMS bioconjugate was immobilized on a glassy carbon electrode?GCE?.The presence of S.aureus was detected by analyzing the change in peak current after the antigen-antibody complex was formed.Differential pulse voltammetry?DPV?was used to detect S.aureus in a concentration range of 10^-2×10³ CFU/mL.The results showed that there was a good linear relationship between the change in peak current and the logarithm of the concentration of S.aureus?R²=0.9759?with short response time?20 minutes?and low detection limit?11 CFU/mL?.In the spiked milk sample test,the performance of the sensor was compared with the colony counting method.The results showed no significant difference in test results.Therefore,the electrochemical immunosensor has the characteristics of high sensitivity,good specificity and strong stability,and can be used to quickly detect S.aureus in milk samples.2 Preparation of an electrochemical enzyme sensor based on magnetic mesoporous hollow carbon spheres and detection of penicillin sodiumPenicillinase?Pen X?-magnetic mesoporous hollow carbon?MMHC?conjugate was used as the detection element to detect low concentration of penicillin sodium?Pen G?.First,MMHC was prepared by using magnetic Fe₃O₄ particles as template.The physical adsorption method was used to immobilize Pen X on MMHC,and the adsorption conditions were optimized.The conjugate was fixed on a magnetic glassy carbon electrode?MGCE?to obtain the working electrode Pen X-MMHC-MGCE.When Pen X reacts with Pen G,H⁺is generated.The increase of H⁺in the solution will cause a redox reaction of hematoxylin,so hematoxylin is used as an indicator to add to the detection solution.The DPV method was used to detect Pen G at a concentration range of 10^-8-10^-22 mg/mL.The results showed a good linear relationship between the peak current value and the logarithm of Pen G concentration?R²=0.9983?,and its LOD was 2.655×10^-7 mg/mL?S/N=3?.The spiked method used to detect Pen G in milk showed good recovery,and the test results were not significantly different from the high performance liquid chromatography method.In addition,the method has the advantages of wide detection range,large amount of enzyme adsorption,fast detection speed,and convenient cleaning and recovery of solid substances,so it can achieve rapid detection of Pen G residues in milk samples.3 Preparation of Electrochemical Enzyme Sensor Based on Rhombus Porous Carbon and Detection of Penicillin SodiumPen X-rhombus porous carbon?RPC?was used as the detection element,and hematoxylin was used as the indicator to detect the low concentration of Pen G content.First,an aluminum-based metal-organic framework?Al-MOF?was prepared,and RPC was prepared by high-temperature calcination using Al-MOF as a template.Pen X was fixed to the material by a chemical covalent bonding method,and the loading conditions were optimized.Fix it on GCE to get working electrode Pen X-RPC-GCE.The DPV method was used to detect Pen G at a concentration range of10^-8-10^-55 mg/mL.The results showed that there was a good linear relationship between the peak current value and the logarithm of Pen G concentration?R²=0.9915?,and the LOD was 2.68×10^-7 mg/mL?S/N=3?,the actual milk sample was detected by the standard addition method and compared with the HPLC method,the test results were not significantly different.The material used in this method is simple in preparation method,the response current of the working electrode is large,the stability is good,the detection time is fast,and it can be used to detect Pen G residues in actual milk samples.