Uniform Lipopolysaccharide (LPS)-Loaded Magnetic Nanoparticles for the Investigation of LPS-TLR4 Signaling

Preparation of Robust Metal-Free Magnetic Nanoemulsions Encapsulating Low-Molecular-Weight Nitroxide Radicals and Hydrophobic Drugs Directed Toward MRI-Visible Targeted Delivery

With a view to developing a theranostic nanomedicine for targeted drug delivery systems visible by magnetic resonance (MR) imaging, robust metal-free magnetic nanoemulsions (mean particle size less than 20 nm) consisting of a biocompatible surfactant and hydrophobic, low molecular weight 2,2,5-trimethyl-5-(4-alkoxy)phenylpyrrolidine-N-oxyl radicals were prepared in pH 7.4 phosphate-buffered saline (PBS). The structure of the nanoemulsions was characterized by electron paramagnetic resonance spectroscopy, and dynamic light scattering and small-angle neutron-scattering measurements. The nanoemulsions showed high colloidal stability, low cytotoxicity, enough reduction resistance to excess ascorbic acid, and sufficient contrast enhancement in the proton longitudinal relaxation time (T₁ ) weighted MR images in PBS in vitro (and preliminarily in vivo). Furthermore, the hydrophobic anticancer drug paclitaxel could be encapsulated inside the nanoparticles, and the resulting paclitaxel-loaded nanoemulsions were efficiently incorporated into HeLa cells to suppress cell growth.

Interference of silica nanoparticles with the traditional Limulus amebocyte lysate gel clot assay

Endotoxin contaminations of engineered nanomaterials can be responsible for observed biological responses, especially for misleading results in in vitro test systems, as well as in vivo studies. Therefore, endotoxin testing of nanomaterials is necessary to benchmark their influence on cells. Here, we tested the traditional Limulus amebocyte lysate gel clot assay for the detection of endotoxins in nanoparticle suspensions with a focus on possible interference of the particles with the test system. We systematically investigated the effects of nanomaterials made of, or covered by, the same material. Different types of bare or PEGylated silica nanoparticles, as well as iron oxide-silica core shell nanoparticles, were tested. Detailed inhibition/enhancement controls revealed enhanced activity in the Limulus coagulation cascade for all particles with bare silica surface. In comparison, PEGylation led to a lower degree of enhancement. These results indicate that the protein-particle interactions are the basis for the observed inhibition and enhancement effects. The enhancement activity of a particle type was positively related to the calculated particle surface area. For most silica particles tested, a dilution of the sample within the maximum valid dilution was sufficient to overcome non-valid enhancement, enabling semi-quantification of the endotoxin contamination.