Mechanistic Investigation of Surfactant-Free Emulsion Polymerization Using Magnetite Nanoparticles Modified by Citric Acid as Stabilizers

Fe₃O₄-armored latexes were successfully synthesized by using modified Fe₃O₄ (IO) nanoparticles as stabilizers without a surfactant. The particle size, conversion, and particle number density of latex particles during the formation process were studied in detail. The surface charge density and the particle size evolutions of latexes were studied by dynamic light scattering. The use of scanning electron microscopy confirmed that IO nanoparticles were adsorbed on the polymer particle surface. Furthermore, the efficiency of iron oxide incorporation (IE) was evaluated by thermogravimetric analysis. The effect of pH, solid content, and zeta potential of IO nanoparticles on the results of polymerization was also discussed in detail. Attempts were made to explain the change of latex particle surface charge density by using Guy-Chapman-Stern's electric double layer theory. In addition, the effect of ionic strength of ammonium sulfate on particle number density of latex particles was described using P. John Feeney's equation. Finally, the mechanistic insights were discussed by studying polymerization kinetics.

Superparamagnetic microsphere-assisted fluoroimmunoassay for rapid assessment of acute myocardial infarction

Rapid assessment of acute myocardial infarction (AMI) was successfully demonstrated using an improved superparamagnetic polymer microsphere-assisted sandwich fluoroimmunoassay to detect two early cardiac markers-myoglobin and human heart-type fatty acid binding protein (H-FABP). This assay used a preparation of superparamagnetic poly(styrene-divinylbenzene-acrylamide) microspheres, glutaraldehyde-coupled capture antibodies (monoclonal anti-myoglobin 7C3 and anti-H-FABP 10E1) grafted onto the polymer microspheres, and a sequential sandwich fluoroimmunoassay using detection antibodies (FITC-labeled anti-myoglobin 4E2 and FITC-labeled anti-H-FABP 9F3). Characterization of the polymer microspheres by TEM, SEM and Fourier transform infrared spectroscopy (FT-IR) showed that the microspheres were uniformly round with an average diameter of 1.12 microm, and had a Fe(3)O(4)-polymer core-shell structure (shell thickness was about 84 nm) with 0.22 mmol/g amino groups on their surfaces. The magnetic behavior of the Fe(3)O(4)-polymer microspheres was superparamagnetic (M(s)=13 emu/g, H(c)=13.1 Oe). Fluorescence images of the post-immunoassay microspheres recorded using a confocal laser-scanning microscope showed that the average fluorescence intensity was correlated with the concentration of cardiac markers, in agreement with the results obtained by an F-4500 FL spectrophotometer; this indicated that the fluoroimmunoassay could be used to semi-quantitatively detect both myoglobin and H-FABP. The detection limit was 25 ng/mL for myoglobin and 1 ng/mL for H-FABP.

The Biological Effect of Iron Oxide and Its Hydrate Nanoparticles

Iron oxide and its hydrate nanoparticles were synthesized by hydrothermal method and confirmed by infrared and SEM (Scanning Electron Microscope) et al. The dimensions of the nanoparticles are about 50-120 nm. The crystalline form of iron oxide nanoparticles is like globosity while its hydrate rod. Amino acids intermingling with the synthesized nanoparticles were crystallized to investigate the space effect of the nanoparticles. The crystalline forms of crystal are different to that of pure amino acid. The positions and width of the nanoparticles’ peaks in the infrared spectrum are changed too. Microscope observation and infrared spectrum results indicated the nanoparticles had changed the internal structure of amino acids crystal. To considerate the toxicity of the synthesized nanoparticles, MTT (3-(4,5-dimethylthiazol 2-yl)-2,5 diphenyltetrazolium bromide) assay was used to determine their cytotoxicity. The OD value (Optical Density) was used to calculated RGR% (Relative Generation Rate) of cells, which determined the grade of cytotoxicity. The RGR of nanoparticles of iron oxide and its hydrate are about 1 to 2, which indicate they have just low toxicity.

Immobilization of lipase onto micron-size magnetic beads

A novel and economical magnetic poly(methacrylate-divinylbenzene) microsphere (less than 8 microm in diameter) was synthesized by the modified suspension polymerization of methacrylate and cross-linker divinylbenzene in the presence of magnetic fluid. Then, surface aminolysis was employed to obtain a high content of surface amino groups (0.40-0.55 mmolg(-1) supports). The morphology and properties of these magnetic supports were characterized with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and a vibrating sample magnetometer. These magnetic supports exhibited superparamagnetism with a high specific saturation magnetization (sigma(s)) of 14.6 emicrog(-1). Candida cylindracea lipase was covalently immobilized on the amino-functionalized magnetic supports with the activity recovery up to 72.4% and enzyme loading of 34.0 mgg(-1) support, remarkably higher than the previous studies. The factors involved in the activity recovery and enzymatic properties of the immobilized lipase prepared were studied in comparison with free lipase, for which olive oil was chosen as the substrate. The results show that the immobilized lipase has good stability and reusability after recovery by magnetic separation within 20s.

Novel, Fluorescent, Magnetic, Polysaccharide-Based Microsphere for Orientation, Tracing, and Anticoagulation: Preparation and Characterization

A fluorescent, magnetic composite poly(styrene-maleic anhydride) microsphere, suitable for conjugation with polysaccharide, was synthesized using magnetite/europium phthalate particles as seeds by copolymerization of styrene and maleic anhydride. The magnetite/europium phthalate particles were wrapped up by poly(ethylene glycol), which improved the affinity between the seed particles and the monomers. The composite microspheres obtained, with a diameter of 0.15-0.7 microm, contain 586-1013 microg of magnetite/g of microsphere and 0.5-16 mmol surface anhydride groups/g of microsphere. Heparin was conjugated with the reactive surface anhydride groups on the surface of the microspheres by covalent binding to obtain a fluorescent, magnetic, polysaccharide-based microsphere. The microspheres not only retain their bioactivities but also provide magnetic susceptibility and fluorescence. They can be used as a carrier with magnetic orientation and fluorescence tracer for potent drug targeting. The orientation, tracer, and anticoagulation of the fluorescence, magnetic, polysaccharide-based microspheres were studied. The anticoagulant activity of the microspheres and heparin binding capacity reached 54,212.8 U and 607.1 mg/g of dry microspheres. The activity recovery was 50.2%. The anticoagulant activity of the microspheres increases with the increase of the conjugated heparin on the surface of the microspheres and the decrease of the microsphere size. Furthermore, The fluorescent, magnetic, polysaccharide-based microspheres can be easily transported to a given position in a magnetic field and traced via their fluorescence.