A magnetite-only hydrogel was prepared for the first time by weak base mediated gelation of stable magnetite hydrosols at room temperature. The hydrogel consists of 10 nm magnetite nanoparticles linked by interparticle Fe-O-Fe bonds and has the appearance of a dark-brown viscous thixotropic material. The water content in the hydrogel could be up to 93.6% by mass while volume fraction reaches 99%. The material shows excellent biocompatibility and minor cytotoxic effects at concentrations up to 207 μg mL. The gel shows excellent sorption capacity for heavy metal adsorption such as chrome and lead ions, which is 225% more than the adsorption capacity of magnetite nanoparticles. Due to thixotropic nature, the gel demonstrates mechanical stimuli-responsive release behavior with up to 98% release triggered by ultrasound irradiation. The material shows superparamagnetic behavior with a coercivity of 65 emu g at 6000 Oe. The magnetite gels prepared could be used for the production of magnetite aerogels, magnetic drug delivery systems with controlled release and highly efficient sorbents for hydrometallurgy.
Nanostructured
drugs are being approved for clinical use, although
there is a serious deficit of systematic studies of these materials.
Data on toxicity of nanoparticles (NPs) can vary due to different
methods of preparation, size, and shape. We investigated the toxicity
against cultured human cells, the acute toxicity in mice, and the
influence on conjugative transfer of antibiotic resistance genes of
clinically relevant NPs such as TiO2, ZrO2,
HfO2, Ta2O5, Fe3O4, and AlOOH. NPs were synthesized as aqueous sols by the same
method in aqueous solution, with almost identical size 2–10
nm. None of these NPs was cytotoxic at concentrations compatible with
water solubility. Furthermore, TiO2, HfO2, Ta2O5, Fe3O4, and AlOOH were
not toxic to mice after oral administration. However, ZrO2 showed rather high toxicity, with LD50 2277.8 mg/kg.
Experiments with plasmid transfer between bacteria demonstrated that
AlOOH NPs were the most hazardous since this material promoted the
emergence of resistance to antibiotics. Thus, although our metal oxide
NPs are largely non-toxic, their properties may differ in specific
biological situations.
Nanocontainers based solely on magnetite NPs have been synthesized by indirect gelation of stable magnetite hydrosol at ambient temperature using the microemulsion-assisted sol-gel method. Containers synthesized have adjustable size and consist of ∼10 nm magnetite nanoparticles linked by Fe-O-Fe interparticle bonds. The material demonstrates high magnetization values up to 60 emu/g and low cytotoxicity against both HeLa and postnatal human fibroblast (up to 260 μg/mL). The systems developed are perspective as a drug depot, particularly for magnetically controlled thrombolysis.
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