Preparation And Characterization Of Magnetic Polymer Microspheres With Carboxyl Group

In the field of biomedical research, magnetic microsphere was widelyused in immunoassay, gene and drug delivery, protein separation andpurification, also the separation of cell and DNA. Relative to traditional tumorcells detection methods, magnetic microsphere owned the advantage of fast,low cost and high performance. The purpose of this paper were used a simpleand effective way to obtained a kind of size controled polyfunctional carboxylmagnetic microspheres with high saturation magnetization. Thesuperparamagnetic Fe3O4nanoparticles were prepared by co-precipitationmethod, and then the nanoparticles were modified by surface active agents toenhanced lipophilic characteristics were prepared; magnetic microsphereswere prepared by dispersion polymerization, using styrene/methylmethacrylate/methacrylic acid as polymeric monomer in aqueous system,divinylbenzene as crosslinker agent, polyvinyl alcohol (PVA) as the dispersing agent, benzoyl peroxide(BPO) as the initiator. Micron level spherical magneticmicrospheres with narrow size distribution, high magnetic content, highsaturation magnetization and high surface carboxyl group were prepared. Theparameters influencing the diameter and size distribution of magneticmicrospheres, including kind of polymerization monomer, initiatorcomposition and content, stirring speed, dispersing agent content,polymerization temperature, content of magnetic fluid and functionalmonomer content were discussed. The size and size distribution ofmicrospheres, the content of magnetic Fe3O4nanoparticles, saturationmagnetization and the amount of–COOH on the surface were investigated byXRD, TGA, VSM, FTIR and conductometric titration. In the following work,a preliminary testing on the application of magnetic microsphere in thedetection of tumor cells was given. The reactivity of carboxyl group on thesurface of magnetic microspheres was established by the result of fluorescencemicroscope images and laser scanning confocal microscope (LSCM) images.Main results of this paper were as follows:(1) Magnetic fluid with good stability was the premise of preparation.Superparamagnetic Fe3O4nanoparticals were double-layer modified. Themodified Fe3O4nanoparticals could be both formed stable suspension inaqueous solution and the compatibility of Fe3O4nanoparticals with monomerswere solved.(2) The compatibility of styrene and methacrylic acid(MAA) were improved by adding methyl methacrylate(MMA). The self-polymerization ofMAA reduced and more MAA was inclined to polymerize on the surface ofmagnetic microspheres.(3) Through the optimization of synthesis conditions, microspheres withexcellent sphericity and even particle size were prepared. The diameter ofmicrospheres range from5μm to180μm, magnetic content reached28%,saturation magnetization up to18.352emu/g and the surface carboxyl densitywas0.063mmol/g. The result of VSM also indicated that the microsphereswere superparamagnetic.(4) The experiment of second fluorescent antibody adsorption showedthat the active carboxyl groups on the surface of magnetic microspheres couldcouple with IgG.