Synthesis Of Fe₃O₄@Cu Nanozyme And Its Applications For Tetracycline Detection

Tetracycline is one of the currently available low-cost broad-spectrum antibiotics.It is widely used in the treatment of bacterial,protozoan and fungal infections in human diseases,livestock production and aquaculture,and it has important value in use.Due to the significant effects of tetracycline in preventing and treating diseases,abuses often occur during use.The tetracycline abuse can cause tetracycline residues in animal food.Besides,human's Long-term exposure to low levels of antibiotics can cause allergic reactions,damage to the liver and intestines,and even lead to the development of potentially resistant bacteria.Therefore,development of tetracycline detection methods with high selectivity and sensitivity has become a hot issue of research in the field of tetracycline detection.The traditional methods have many flaws,Such as high cost,complicated operation,and expensive instruments.Comparing to that,biosensors that combine nanozyme signal amplification technology,aptamer specific recognition and colorimetric visualization sensor assay has been widely researched and applied.Because they do not only have higher Sensitivity,strong specificity,but also simple operation,short time consumption,low sample consumption,and low analysis cost.In this paper,the iron oxide nanozyme was synthesized by the solvothermal route,and the core-shell nanozyme Fe₃O₄@Cu was synthesized by the redox method.The combination of Fe₃O₄@Cu nanozyme and aptamer has established two simple and fast colorimetric sensors with good selectivity,high sensitivity,low cost,which are used for the detection of tetracycline.?1?Preparation and characterization of nanozymeThe iron oxide nanozyme was synthesized by the solvothermal route,and the core-shell nanozyme Fe₃O₄@Cu was synthesized by the redox method.Fe₃O₄ and Fe₃O₄@Cu were characterized by ultraviolet-visible spectrophotometer,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and nanoparticle size analyzer.The kinetic experiments show that the Km of Fe₃O₄ and Fe₃O₄@Cu are lower than that of horseradish peroxidase.These indicate that the nanozyme synthesized in this paper shows a higher affinity for substrate.Stability experiments show that the catalytic activity of Fe₃O₄@Cu has high stability.And it can still maintain 60%of the original activity at room temperature for three months.?2?Tetracycline in milk was detected by a"turn off"colorimetric sensor based on nanozyme and aptamerAptamer was used as a recognition element,based on the ability of Fe₃O₄@Cu to adsorb single-stranded DNA of different lengths,a"turn off"colorimetric sensor was developed for the detection of tetracycline in milk.To achieve a higher level of sensitivity,several key parameters of the proposed method such as concentrations of casie,cDNA-1,aptamer and cDNA-2 have been investigated.Under optimal conditions,the sensor can detect tetracycline in a linear range from 10^-2?g/L to 10³?g/L with a limit of detection?LOD?as low as 0.01?g/L.Moreover,further studies also validate the applicability of the sensor in milk samples with the recovery rate ranging from 71.79%to 111.54%.?3?Tetracycline was detected by a"turn on"colorimetric sensor based on nanozyme and aptamerAptamer was used as a recognition element,based on the different adsorption ability of Fe₃O₄@Cu for single-stranded DNA and double-stranded DNA,a"turn on"colorimetric sensor was developed for the detection of tetracycline.In this paper,the concentration of cDNA-1 was optimized,and the hybridization of cDNA-1 and APT was verified by agarose gel electrophoresis.The results demonstrated that the sensor has successfully detected tetracycline.The sensor can detect tetracycline in a linear range from 10 mg/L to 80 mg/L with a limit of detection as low as 0.688 mg/L.