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Abstract

Three kinds of dextran-magnetite (DM) complexes were prepared using alkali-treated dextrans with molecular weights of 1900, 4200 and 9600, respectively. The number of dextrans binding to a magnetite core was determined. The number was proportional to the area of core surface and the area occupied by a dextran was 2.5 nm2 for molecular weight of 1900, 2.8 for 4200 and 3.8 for 9600. The binding of dextrans to core may be conditioned by the conformation of dextran chains in water (possibly by the steric hindrance between dextrans covering core). Stability of the DM solution was examined at 80 degrees C. Aggregation and/or precipitation of DM particles were observed within two weeks. The stability of DM solution was found to increase with increasing molecular weight of dextran. The dissociation of dextran from the core may cause the aggregation and subsequent precipitation of DM particles (the dissociation constant at 20 degrees C, 3.7 x 10(-6) for a molecular weight of 1900 and 5.4 x 10(-7) for 9600).

Antioxidant cerium oxide nanoparticle hydrogels for cellular encapsulation

“…The long-term stability of the CONPs within the alginate hydrogel is likely to due to dynamic exchange of the dextran coating of the CONPs with alginate, due to the instability of the physiosorbed dextran [64]. This phenomenon has been reported for iron oxide nanoparticles, whereby the COO− terminal of alginate macromolecules binds to the nanoparticle in a manner identical to dextran, even forming the classic “egg-box” structure as a result of interactions between alginate macromolecules and oxide vacancies of the nanoparticles [65-67]. While this study exhibits the utility of dextran coated CONPs for retention within alginate, it is envisioned that other nanocomposite materials could be engineered, such as through covalent tethering of coated CONPs to functionalized poly(ethylene glycol).…”

Effects of organic polymer addition in magnetite synthesis on the crystalline structure

“…12 In the preparation of inorganic-organic hybrids, the chemical structure or molecular weight of the added polymer affects the ionic interaction between polymer and iron salts as well as the grain size and morphology of the prepared Fe 3 O 4 core. 13,14 The heat generation properties are drastically dependent on the particle size of the Fe 3 O 4 nanoparticles, because Fe 3 O 4 converts from ferromagnetic into superparamagnetic with a decrease in particle size. 15,16 The in situ precipitation of Fe 3 O 4 with 13 mm average diameter particles in cationic chitosan hydrogels 17 and the crystal phase control of the iron oxide were attempted in an aqueous solution with ethylenediaminetetraacetic acid.…”

Colloidal dispersions of monodisperse magnetite nanoparticles modified with poly(ethylene glycol)

“…Polymers and natural polymer-like materials have been used as surfactants to stabilize the particles. Examples include dextran [20][21][22], chitosan [23], poly(vinyl alcohol) [24], poly(ε-caprolactone) [25,26], and poly(ethylene glycol) [27]. Among these polymers, poly(ethylene glycol) (PEG) is of great interest, specially in biological applications since it has been shown to enhance particle stability in water due to its high solubility.…”