Construction Of Electrochemical Sensors Based On New Carbon Nanomaterials And Their Application In Meat Quality And Safety Evaluation

Food safety has been obtained more and more attention with the improvement of people’s living standard.The main factors which determine the consumer buying motivation were sensory（appearance,taste,and sensation）,safety,and nutritional characteristics in meat and meat product.Antibiotics which could inhibit bacteria and promoted the growth of plants and animals were widely applied in food production and animal husbandry.Kanamycin,as one of the most commonly used aminoglycoside antibiotics,would cause residues in animal and cause indirect severe side effects on the human body if uncontrolled and incorrect use.Therefore,the residue of antibotics in meat products was one of the food safety issues that consumers focused on.Hydroxyl radicals were highly reactive reactive oxygen radicals with strong oxidizing properties which would cause lipid chain oxidation,meat spoilage,and seriously affected the color,smell,flavor and nutritional properties.Biological amines,as a general term for a class of biologically active nitrogen-containing organic compounds,were widely exsited in various of foods rich in amino acids and proteins,of which histamine had the greatest impact on human health.Therefore,the research objective of this paper was to quantitatively detect kanamycin,hydroxyl radicals and histamine in order to evaluate the food safety of meat products.Carbon nanomaterials,as an important part of new materials,had attracted great attention of researchers.New carbon nanomaterials including graphene,carbon nanotubes,carbon fibers,fullerenes,and nitrogen-doped carbon nanomaterials were widely applied in electrochemical sensors due to the good biocompatibility,large specific surface area,non-toxicity,good electrical conductivity,and unique optical electrical properties.In this paper,new carbon nanocomposites based on graphene,carbon nanotubes and carbon nitride were prepared and used to construct electrochemical sensors to detect kanamycin,hydroxyl radicals and histamine.The specific research content was as follows:1.In this chapter,the heme/reduced graphene oxide/carboxylated carbon nanotube（rGO-Hemin-cMWCNTs）ternary composite was prepared and characterized.And the electrochemical aptamer sensor was constructed to detect kanamycin based on rGO-Hemin-cMWCNTs.Hemin presented good electrochemical activity and could be used as an electrochemical signal molecule due to a pair of reversible redox peaks of iron ion in the porphyrin ring.Reduced graphene oxide presented good electrochemical performance and heme was successfully supported on reduced graphene oxide through theπ-πinteraction.The introduction of carboxylated carbon nanotubes could amplify electrochemical signals and provide carboxyl functional groups.The differential pulse voltammetry（DPV）method was empoyed to detect kanamycin under the optimal experimental conditions.And the relationship between the electrochemical response and kanamycin concentration was obtained.The linear equation was△I（μA）=15.9716 log C_（KANA）+198.673（R²=0.9960）,△I=I₀–I,I₀ represented the current of aptamer/rGO-Hemin-cMWCNTs/GCE sensor which was not combined with kanamycin and I represented the current of aptamer/rGO-Hemin-cMWCNTs/GCE sensor which combined with different concentrations of kanamycin.The linear range was from 10^-12to 10^-6 M and the detection limit was 1 p M.The prepared sensor showed a good selectivity,low detection limit and wide linear range and could be used to quantitative detection of kanamycin.2.In this chapter,carboxylated-g-C₃N₄NPs were successfully prepared by molten salt method and fixed on the surface of the sensor.The electrochemical sensor based on MB/ss DNA/carboxylated-g-C₃N₄ NPs/chitosan/GCE was constructed and methylene blue（MB）was used as signal molecule due to the electrostatic interaction between MB and DNA strands.Considering the DNA strands could be oxidized and broke by^·OH,different concentrations of^·OH would cause different extents of broken the ss DNA which immobilized on the electrode and combined different amounts of MB,resulting in different electrochemical signals.The square wave voltammetry（SWV）was employed to detect^·OH.Due to the equation of Fe²⁺+H₂O₂→Fe³⁺+OH^-+^·OH,the concentration of Fe²⁺was used to represent the concentration of^·OH in this experiment.The linear regression equation between current difference（△I）and the concentration of Fe²⁺was△I（μA）=0.9512 log[Fe²⁺]+2.3941（R²=0.9973）,△I=I₀-I,I₀ and I were the peak currents of MB obtained from electrodes before and after incubated with various concentration of Fe²⁺.The linear range was from 2 10^-6to1.0 10^-2M and the detection limit was 8 10^-7 M（S/N=3）.In addition,four actual samples of shrimp,chicken,pork,and sausage were spiked,and the obtained results were compared with the electronic spin resonance method（ESR）,there was no significant difference between electrochemical methods and ESR.The results showed that the sensor could be applied to the rapid detection of^·OH in meat,which presented potential food safety application value.3.In this chapter,the reduced graphene oxide-polypyrrole（rGO-PPy）composites was synthesized and the electrochemical sensor was constructed to detect histamine based on rGO-PPy.The experiment showed that histamine had a good electrochemical response in an alkaline phosphate buffer solution（pH=12）based on rGO-PPy sensor and the oxidation reaction was occured.Differential pulse voltammetry（DPV）was adopted to quantify histamine under the optimal experimental conditions.The peak current value was linear with the concentration of histamine.The linear regression equation was I（μA）=0.01047C_{（histamine）}+0.1842（R²=0.9970）with the limit of 3.2μM,and the linear range from 10 to 800μM.Compared with other methods,the experimental results showed that the electrochemical sensor prepared presented a relatively low detection limit and a wide linear range.The sensor showed a good application prospect for the detection of histamine.