Magnetic microgels, a promising candidate for enhanced magnetic adsorbent particles in bioseparation: synthesis, physicochemical characterization, and separation performance

Abstract

For specific applications in the field of high gradient magnetic separation of biomaterials, magnetic nanoparticle clusters of controlled size and high magnetic moment in an external magnetic field are of particular interest. We report the synthesis and characterization of magnetic microgels designed for magnetic separation purposes, as well as the separation efficiency of the obtained microgel particles. High magnetization magnetic microgels with superparamagnetic behaviour were obtained in a two-step synthesis procedure by a miniemulsion technique using highly stable ferrofluid on a volatile nonpolar carrier. Spherical clusters of closely packed hydrophobic oleic acid-coated magnetite nanoparticles were coated with cross linked polymer shells of polyacrylic acid, poly-N-isopropylacrylamide, and poly-3-acrylamidopropyl trimethylammonium chloride. The morphology, size distribution, chemical surface composition, and magnetic properties of the magnetic microgels were determined using transmission electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Magnetically induced phase condensation in aqueous suspensions of magnetic microgels was investigated by optical microscopy and static light scattering. The condensed phase consists of elongated oblong structures oriented in the direction of the external magnetic field and may grow up to several microns in thickness and tens or even hundreds of microns in length. The dependence of phase condensation magnetic supersaturation on the magnetic field intensity was determined. The experiments using high gradient magnetic separation show high values of separation efficiency (99.9-99.97%) for the magnetic microgels.

Magnetic iron oxide nanoparticles: Recent trends in design and synthesis of magnetoresponsive nanosystems

“…Magnetically induced linear aggregates can occur in both single core [55,56] and multicore liquid dispersions [57,58]. The magnetically induced phase condensation in single core liquid dispersions can show critical behavior: below a critical temperature (Tc) the condensation occurs only at field intensities larger than a critical value…”

“…Densely packed magnetic multi-core in thermoresponsive polymer shell obtained by ferrofluid miniemulsion procedure provided high magnetization spherical particles [57,96], promising for both efficient magnetic drug delivery and temperature controlled release. The surface density of oleic acid coating of individual MNPs controls the morphology of MNP clusters resulting in the oil-in-water miniemulsion process [50].…”

“…(3) miniemulsion: left -TEM images of magnetic microgel with magnetite nanoparticles cluster as a core coated with two layers of cross linked polymer shells poly-N-isopropylacrylamide-polyacrylic acid(Reproduced from Ref. [57] with permission of The Royal Society of Chemistry); center -TEM image of magnetic clusters encapsulated in a copolymer hydrogel poly(N-isopropylacrylamide-acrylic acid). Scale bar: 100 nm.…”

Seismic Protection of Structures Using a Hybrid System: Buckling Restrained Brace and Magneto Rheological Damper

“…The conceptual scheme of the MR damper is illustrated in Figure 2. As can be observed, the hybrid solution implies a hydraulic damper equipped with a control cell which uses nano-micro magneto-rheological fluid developed within the current research project by the partner institutions [5] [6]. It is to be highlighted that the advantage of the adopted solution resides in the reduction of the volume of MR fluid, and the corresponding costs.…”

The effect of magnetic nanoparticle concentration on the structure organisation of a microferrogel

“…Microferrogels (magnetic microgels, microscopic ferrogels, MFGs) are isolated soft polymers objects with typical sizes in the range of 0.1-10 μm containing embedded magnetic nanoparticles (NPs); typical NP materials are magnetite and cobalt ferrite [1,2]. Strong coupling between the magnetic NPs and the polymer mesh, in which the NPs take on the role of cross-linkers, ensures the dependence of mechanical and structural properties of a MFG object on the external magnetic field.…”