Synthesis and Characterization of Paramagnetic Microparticles through Emulsion-Templated Free Radical Polymerization

Abstract

A novel method is described for the preparation of high-magnetization paramagnetic microparticles functionalized with a controlled density of poly(ethylene glycol) (PEG) and carboxyl groups. These microparticles were synthesized using four steps: (1) creation of an oil-in-water emulsion in which hydrophobic iron oxide nanoparticles and a UV-activated initiator were distributed in hexane; (2) formation of uniform microparticles through emulsion homogenization and evaporation of hexane; (3) functionalization of the microparticle with a PEG-functionalized surfactant and acrylic acid; and (4) polymerization of the microparticles. Characterization of the microparticles with electron microscopy and light scattering revealed that they were composed of densely packed iron oxide nanoparticles and that the size of the microparticles may be controlled through the pore size of the membrane used to homogenize the emulsion. The concentration of surfactant and acrylic acid used in the third processing step was found to determine the surface chemistry, iron content, and magnetization of the microparticles. Increasing the PEG surfactant to acrylic acid ratio resulted in higher PEG surface densities, lower iron content, and lower magnetization. The resulting microparticles were readily functionalized with antibodies and showed a low propensity for nonspecific protein adsorption. We believe that these microparticles will be useful for magnetic tweezers measurements and bioanalytical devices that require microparticles with a high magnetization.

Study of preparation and properties on polymer-modified magnetite nanoparticles

“…The pure Fe 3 O 4 lost 13.3 % of its total weight, which is probably due to the absorbed water from the environment. 8 The PAM-modified samples show that there are three stages of mass loss for the thermal degradation of PAM. The first stage involves a slight weight loss around 9 % at temperature below 250°C.…”

“…The saturation magnetization of the nanoparticles is significantly smaller than that of bulk magnetite which is 84 emu g -1 . 8 It is believed that the decrease of measured saturation magnetization can be attributed to the reduction of size and the PAM coating. 1,7,8,12 RESEARCH ARTICLE R. Tong, Y. Wang, G. Yang, A. Ma, K. Sun, H. Yang and J. Wang, 101 S. Afr.…”

“…6,7 However, pure Fe 3 O 4 nanoparticles are likely to aggregate for their large specific surface area and strong magnetic dipole-dipole attractions between nanoparticles, resulting in aggregation in aqueous solution and the change of magnetic properties which should be avoided in applications. 8 To avoid the aggregation of pure Fe 3 O 4 nanoparticles during the application processes as mentioned above, modification on the surface of Fe 3 O 4 nanoparticles with a surfactant or hydrophilic polymer is one of the most effective methods. 9,10 Furthermore, another significant function of the modification on the nanoparitcles is that the polymer or surfactant provides chemical groups for further grafting to satisfy further applications.…”

Synthesis and Assembly of Gold and Iron Oxide Particles Within an Emulsion Droplet; Facile Production of Core@Shell Particles

“…The magnetic properties of the beads were measured with a superconducting quantuminterference device (SQUID) magnetometer (Quantum Design, San Diego, CA, USA) at room temperature as described previously [23].…”

Isolation of Bowman-Birk-Inhibitor from soybean extracts using novel peptide probes and high gradient magnetic separation

“…Superparamagnetic particles were synthesized according to an emulsion solvent evaporation procedure developed in our lab (Shang, 2006; Muzard, Platt and Lee, to be published elsewhere). The magnetic properties of the particles were determined using a Quantum…”