Polystyrene-coated Magnetic Nanocomposite For Enzyme Immobilization

The small size effect of nanomaterials and the effect of surface and interfacemagnetic nanoparticles with special magnetic properties different from conventional bulkmagnetic materials. Magnetic nanomaterials in the mainstream biomedical applications inthe long run is very promising, and has made important progress, including theoverheating treatment of drug delivery, magnetic fluid, magnetic resonance imaging andmagnetic bioseparation.Uniform Size Nanoparticles strong pursuit of their technology and the importance ofbasic science, these nanoscale materials often exhibit very interesting electrical, optical,magnetic and chemical properties of their bulk materials do not have. Physical, biologicaland chemical methods of synthesis methods of magnetic nanoparticles, the mostcommonly used chemical method, chemical method can be divided into co-precipitationmethod, the pyrolysis method, microemulsion method, hydrothermal synthesis, sol-gelreaction polyol method, sonochemical method. Magnetic nanoparticles because of itsunique magnetic properties has also become one of the most popular materials used inbiomedical and biotechnology fields, more and more targeted drugs, such as magneticcell separation, magnetic resonance imaging, immunoassay, biological sensing, DNA andRNA purification and enzyme immobilization, etc.. As part of the immobilized enzyme,the structure and performance of the carrier material have a huge impact on the variousproperties of the immobilized enzyme. Compared with traditional organic polymer carrier,inorganic carrier, as well as some of the new carrier （such as ultrasonic modificationcarrier, photosensitive monomer polymers, etc.）, the magnetic nanoparticles as enzymeimmobilization carriers, with the incomparable advantages of the other carrier material.Single particle magnetic response is weak, can not be easily recycled; bare particlesand chemical stability. Therefore, in order to achieve enzyme immobilization to theparticle surface modification. We modified magnetic nanoparticles are collectivelyreferred to as magnetic microspheres. We often inorganic materials using small organic molecules, organic polymer and SiO₂nanoparticles surface modified nanoparticlesthrough the modification of small molecules, there are still some problems in the stabilityof the magnetic response of the current regular use of polymer particle surfacemodification, a different approach to the system of polymer magnetic microspheres. Inaddition, the modification of organic polymer can be produced with more than one carrierof the magnetic core, the vector magnetic responsiveness, making it easy to recycle; theexistence of the particle surface shell also gives physical and chemical stability of theparticles to improve the particle acid, antioxidant capacity. With SiO₂magneticnanoparticles surface modified, aerosol pyrolysis method, microemulsion method and themethod of Stober method in the system SiO₂magnetic microspheres.Crosslinking by adsorption, chelation, embedded and co-precipitation method, canbe immobilized magnetic microspheres as a carrier of the enzyme. However, in a varietyof enzyme immobilization methods, covalent binding method is the application andreported that a class method, so we use magnetic beads specific functional groups（carboxyl, amino, epoxy, hydroxyl） through a variety of coupling methods and enzymecovalent coupling to achieve the immobilization of enzyme. Finally, we analyze theperformance of the magnetic beads immobilized enzyme, including the vitality of theimmobilized enzyme, the stability of the immobilized enzyme, the immobilized enzymeoptimum pH value and the optimum temperature of immobilized enzyme kineticscharacteristics. Which the type of enzyme, magnetic beads （immobilized） the nature ofthe method of immobilization, immobilization conditions and so may the activity of theenzyme will have an impact.The content of this thesis is as follows:Synthesis and Characterization of Fe₃O₄nanoparticles. Sun Shouheng reported underN2atmosphere, acetyl acetone iron [Fe （acac）3] for the iron precursor, oleic acid andoleylamine as a stabilizer,1,2-12diol as a reducing agent300℃under the conditions inthe high-boiling point solvent benzyl ethers have been successfully synthesized a high degree of single-dispersion, particle size uniform Fe₃O₄nanoparticles. Reported in theliterature1,2-hydrocarbon diols include1,2-36diols （1,2-hexadecanediol） and1,2-12diols （1,2-dodecanediol） can be well with Fe （acac）3reaction to produce Fe₃O₄nanoparticles, can also be used long-chain alcohols such as octadecanol （stearyl alcohol）and oleyl alcohol （oleyl alcohol）, but of Fe₃O₄nanoparticles with diols poor quality andlow production. Therefore, we chose the cheaper than1,2-36diols1,2-12diol as areducing agent. We synthesized Fe₃O₄nanoparticles dispersed in hexane,18months lateris still very stable, no precipitation. Were characterized by the synthesis of Fe₃O₄nanoparticles, TEM showed that the size is about8nm;Synthesis and Characterization of composite particles of Fe₃O₄/Polystyrene The oilphase synthesis of oleic acid-modified Fe₃O₄nanoparticles for the miniemulsion wasprepared Fe₃O₄/Polystyrene composite particles, the Fe₃O₄/Polystyrene compositeparticles as shown. It can be seen from the TEM composite particle of Fe₃O₄/Polystyrenepresents the rules of spherical composite particle size more uniform particle size of themicrospheres obtained about124nm, with a good monodispersity.Determination of papain activity. Through the the Forint phenol method for thedetermination of the vitality of free papain, combined with the tyrosine standard curve,and measured the vitality of free papain for72679U/g.Magnetic nanoparticles for the immobilization of papain. When the relative activityof the enzyme and the carrier proportion of800mg/g, the temperature of theimmobilized enzyme at70°C and the activity recovery of the maximum. We determinedthe enzymatic properties of the immobilized enzyme, shows that compared with the freeenzyme, the thermal stability of the immobilized enzyme increased, and repeated use offour or more still higher enzyme activity.