Multiresponsive polymer conetworks capable of responding to changes in pH, temperature, and magnetic field: synthesis, characterization, and evaluation of their ability for controlled uptake and release of solutes

This study deals with the preparation of novel multiresponsive (magnetoresponsive, thermoresponsive and pH-responsive) nanocomposite conetworks consisting of oleic acid-coated magnetite nanoparticles (OA·Fe(3)O(4)), hydrophilic/thermoresponsive hexa(ethylene glycol) methyl ether methacrylate (HEGMA), hydrophobic/metal binding 2-(acetoacetoxy)ethyl methacrylate (AEMA), and pH-responsive/thermoresponsive N-diethylaminoethyl methacrylate (DEAEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) moieties. Conventional free radical copolymerization was employed for the synthesis of random conetworks in the absence and presence of preformed OA·Fe(3)O(4). Further, in characterization of these materials in regards to their swelling behavior in organic and aqueous solvents, thermal/thermoresponsive properties, and composition, assessment of their magnetic characteristics disclosed tunable superparamagnetic behavior. These systems were also evaluated toward their ability to adsorb and release a solute (benzoic acid) in a controlled manner upon varying the pH.

A biotechnological perspective on the application of iron oxide magnetic colloids modified with polysaccharides

Iron oxide magnetic nanoparticles (MNPs) alone are suitable for a broad spectrum of applications, but the low stability and heterogeneous size distribution in aqueous medium represent major setbacks. These setbacks can however be reduced or diminished through the coating of MNPs with various polymers, especially biopolymers such as polysaccharides. Polysaccharides are biocompatible, non-toxic and renewable; in addition, they possess chemical groups that permit further functionalization of the MNPs. Multifunctional entities can be created through decoration with specific molecules e.g. proteins, peptides, drugs, antibodies, biomimetic ligands, transfection agents, cells, and other ligands. This development opens a whole range of applications for iron oxide nanoparticles. In this review the properties of magnetic structures composed of MNPs and several polysaccharides (Agarose, Alginate, Carrageenan, Chitosan, Dextran, Heparin, Gum Arabic, Pullulan and Starch) will be discussed, in view of their recent and future biomedical and biotechnological applications.

In situ crosslinkable hydrogel formed from a polysaccharide-based hydrogelator

In situ crosslinkable hydrogel formed from an amphiphilic amylopectin-based hydrogelator in aqueous solution was investigated with respect to its viscoelasticity, structure as well as protein encapsulation and release. Different from the physical hydrogel formed from an aqueous amylopectin system of sufficiently high concentration, such a hydrogel could be formed rapidly at room temperature and exhibit enhanced viscoelastic properties, mechanical strength, and shear thinning behavior. In addition, it has a more complex network structure with a higher fractal dimension due to intermolecular hydrophobic interactions and macromolecular chain entanglements. By circular dichroism analyses and in vitro release experiments, this hydrogel material was found to have a great potential as new matrix for the entrapment and sustained release of bovine serum albumin.

Magnetic hydrogels with supracolloidal structures prepared by suspension polymerization stabilized by Fe(2)O(3) nanoparticles

Magnetic hydrogels with supracolloidal structures were fabricated by suspension polymerization of N-isopropylacrylamide (NIPAm) and/or acrylamide (Am) stabilized by Fe(2)O(3) nanoparticles. Fe(2)O(3) nanoparticles can self-assemble at liquid-liquid interfaces to form stable water in oil Pickering emulsion droplets. Monomers dissolved in suspended aqueous droplets were subsequently polymerized at 60 degrees C. When NIPAm was homopolymerized the PNIPAm produced deposited from the interior water phase onto the interface to form Fe(2)O(3)/PNIPAm nanocomposite shells because of its hydrophobicity at the reaction temperature. Magnetic and thermosensitive hollow microcapsules were obtained. When Am was homopolymerized magnetic core-shell microcapsules with PAm hydrogel cores and Fe(2)O(3) nanoparticle shells were obtained. When NIPAm and Am were co-polymerized, magnetic hydrogel microcapsules with two kinds of supracolloidal structures were obtained varying with the NIPAm/Am ratio. These microcapsule beads may find applications as delivery vehicles for biomolecules, drugs, cosmetics, food supplements and living cells. Suspension polymerization based on Pickering emulsion droplets opens up a new route to synthesize a variety of hybrid hydrogels with supracolloidal structures.

Structural organization of iron oxide nanoparticles synthesized inside hybrid polymer gels derived from alginate studied with small-angle X-ray scattering

The structural organization of iron oxide nanoparticles (NPs) obtained through in situ coprecipitation of iron salts in semi-interpenetrating polymer networks (semi-IPNs) constituted of alginate (Alg) and poly(N-isopropylacrylamide) (PNiPAAm) has been investigated by means of small-angle X-ray scattering and transmission electron microscopy. The oxidation reaction was repeated up to two times to increase the amount of iron oxide NPs formed. The results were compared to the synthesis of iron oxide nanoparticles in an alginate solution. It has been demonstrated that the polymeric gel acts as a spatial framework for iron oxide nanoparticles that controls their particle size distribution and that the application of repeating oxidation cycles does not increase the polydispersity of the iron oxide nanoparticles.

Hydrogel-magnetic nanoparticles with immobilized L-asparaginase for biomedical applications

The association of magnetic nanoparticles, which could be controlled by a magnetic field and have dimensions which facilitate their penetration in cells/tissues, with hydrogel type biopolymeric shells confer them compatibility and the capacity to retain and deliver bioactive substances. The main objective of this work is the development of a new system based on a biocompatible polymer with organic-inorganic structure capable of vectoring support for biologic active agents (L: -asparaginase, e.g.). Characterization of size and morphology of the hydrogel-magnetic nanoparticles with entrapped L: -asparaginase was made using Dynamic Light Scattering method, Transmission Electron Microscopy and Confocal Microscopy. The structure of magnetic nanoparticles coated with hydrogel was characterized by Fourier Transformed Infrared Spectroscopy. The cytotoxicity of nanoparticles was evaluated and also the interactions with microorganisms. We obtained hydrogel-magnetic nanoparticles with L: -asparaginase entrapped, with sizes below 30 nm in dried stage, capable to penetrate the cells and tissues.

Nanostructured Biomaterials with Controlled Properties Synthesis and Characterization

Magnetic nanoparticles were obtained using an adjusted Massart method and were covered in a layer-by-layer technique with hydrogel-type biocompatible shells, from chitosan and hyaluronic acid. The synthesized nanocomposites were characterized using dynamic light scattering, transmission electron microscopy, and Fourier transformed infrared spectroscopy. Biocompatibility of magnetic nanostructures was determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) cell proliferation assay, swelling tests, and degradation tests. In addition, interaction of hydrogel-magnetic nanoparticles with microorganisms was studied. The possibility of precise nanoparticles size control, as long as the availability of bio-compatible covering, makes them suitable for biomedical applications.