Preparation And Characterization Of Magnetic Composite Microspheres And Their Application In Purification Of DNA

Fe3O4 microspheres were prepared by an ethylene glycol reduction method at 200°C. The effects of starting materials on the morphology and crystallinity of the samples were investigated. The samples were characterized with XRD, FTIR, TEM, and VSM. It shows that nearly monodisperse Fe3O4 microspheres have been acquired with high crystalline perfection, a narrow size distribution, and a high magnetic saturation value (Ms) of 89 emu/g.Core-shell structured Fe3O4/SiO2 composite microspheres were respectively prepared by a microemulsion method and a modified St?ber process. The effects of reaction conditions on the morphology, crystallinity, and magetic property of the samples were explored including the content of TEOS and the volume ratio of C2H5OH/H2O, etc. The samples were characterized with XRD, FTIR, XPS, TEM, EDS, ICP–OES, and VSM. It shows that, similar to that of bare Fe3O4 microspheres, the Fe3O4/SiO2 composite microspheres have a narrow size distribution, along with wealthy silanol groups on the surface which warrants their potential application in bioseparations. The Ms values decrease with increasing the thickness of silica coatings, while a relatively high magnetic response remains for each Fe3O4/SiO2 sample.Carboxyl group-containing core-shell structured Fe3O4/polystyrene (PS) composite microspheres were prepared by a disperse polymerization method. The effects of reaction conditions on the experimental results were investigated in detail including the initiator, amount of monomer, ultrasonication treatment, and stabilizer, etc. The samples were characterized by XRD, FTIR, TEM, and VSM. It shows that the resulting products have also a narrow size distribution, wealthy carboxyl groups on their surface, relatively high crystallinity, and high Ms values.Both the Fe3O4/SiO2 and carboxylated Fe3O4/PS magnetic composite microspheres were further used as adsorbents for purification of plasmid DNA from E. coli DH5αcells and genomic DNA from aspergillus niger cells. The results show that the Fe3O4/SiO2 samples are superior to the carboxylated Fe3O4/PS samples in purification of DNA, which is based on the data that, using 10 mg of Fe3O4/SiO2 and 10 mg Fe3O4/PS samples as adsorbents in sequence, 16.3 vs 13.0μg plasmid DNA and 11.0 vs 10.7μg chromosomal DNA can be respectively isolated from 40μL of nuclear acid extract. The purified DNA samples were analyzed by agarose gel electrophoresis and quantified by UV spectrometry. The A260/A280 ratios higher than 1.7 indicate that the isolated DNA samples are of relatively high purity, which warrants them for further applications.