The Preparation Of Magnetic Enzymeinorganic Hybrid Materials And Its Application

Due to the mild reaction conditions,high catalytic efficiency and environmental friendliness,biological enzymes have played an important role in different industries.Free enzymes are usually applied to enzyme-based catalysis processes,but the enzymes are disposable and difficult to reuse,the stability is poor,and storage conditions are relatively harsh.The immobilization of biological enzymes provides an effective solution to the above-mentioned problems.Both magnetic nanoparticles and enzyme-inorganic hybrid nanocomposites are good carriers for enzyme immobilization.Magnetic nanoparticles have a large specific surface area,a high loading rate for enzymes,and can easily separate biological enzymes from the reaction medium with external magnetic fields,but it is difficult to achieve the reuse of enzymes and maintenance of enzyme activities at the same time.Hybrid nanocomposites can usually retain most of the enzyme activities and have high stability,but they have shortcomings such as low loading efficiency for enzymes,difficult separation and recovery,and low mechanical strength.In order to show the advantages of the two materials at the same time,we prepared enzyme-inorganic hybrid magnetic nanocomposites,and used different enzymes to study their roles in biocatalysis and biosensing:(1)Biocatalysis:We selected ?-galactosidase as the organic component and Ca²⁺as the inorganic component.The?-galactosidase-Ca²⁺hybrid magnetic nanocomposite was prepared by a co-precipitation method.Coral-like structures could be observed by a high-resolution scanning electron microscope.The nanocomposite retained most of the free beta-galactosidase activity,and could effectively catalyze the hydrolysis of lactose in milk.In addition,the magnetic nanocomposite also had excellent reusability and good storage stability,after five cycles of use,all the initial enzyme activity can still be maintained,and more than half of the initial enzyme activity can be retained after 20 days of storage at room temperature.It is suitable for the continuous production of lactose-free milk in the food industry.(2)Biosensing:We selected choline oxidase and horseradish peroxidase as organic components,and Cu²⁺as inorganic components to prepare choline oxidase-horseradish peroxidase-Cu²⁺hybrid magnetic nanoflowers by a co-precipitation method and built a colorimetric sensor to detect choline based on the cascade reaction.The higher the concentration of choline in the sample,the more hydrogen peroxide was produced,and thereby catalyzing the oxidation of more colorless substrates into blue-green products.The blue-green product had an ultraviolet-visible absorption peak at 418 nm.Visualized analysis and quantitative detection of choline were achieved by visually observing the color change of the supernatant or measuring the absorbance at 418 nm.The detection limit of this method was 0.42?M.After being washed,the material can be reused,and the?A_{418 nm} value detected after five cycles is about half of the initial value,and the?A_{418 nm} value detected after 15 days of storage is about half of the initial value,holding high storage stability and broad application prospects.