Gold Nanoparticles Dissolve Extracellularly in the Presence of Human Macrophages

Agglomeration compaction promotes corrosion of gold nanoparticles

Engineered nanoparticles are increasingly being used in various areas of human activity. However, the degradation mechanism of nanobodies in harsh environments is still a puzzle for theory and experiment. We report here the results of optical spectroscopy and nanoparticle tracking analysis, quantifying agglomeration and sizing of 50 nm citrate stabilized gold nanoparticles (GNPs) in HCl solutions containing H2O2. The mechanism of a consecutive corrosion reaction of GNPs is discussed within the framework of the near-field approach. We found that the disappearance of single nanoparticles from a suspension does not occur due to their dissolution per se, but is a consequence of the formation of aggregates. The neutralization of electrostatic shielding at high ionic strength allows gold nanoparticles to approach the subnanometer distance within the region of capping defects, at which the Casimir and van der Waals attractive forces dominate. It is suggested that electric field fluctuations in the confined space between highly conductive gold nanoparticles cause complexant-stimulated loss of metal from the core in the contact area. Going beyond the charge screening limitations by constraining the reaction space and reducing the double electrical layer thickness allows for chemical processes flow along otherwise not accessible reaction pathways.

nanoGold and µGold inhibit autoimmune inflammation: a review

The newest data on metallic gold have placed the noble metal central in the fight for the safe treatment of autoimmune inflammation. There are two different ways to use gold for the treatment of inflammation: gold microparticles > 20 µm and gold nanoparticles. The injection of gold microparticles (µGold) is a purely local therapy. µGold particles stay put where injected, and gold ions released from them are relatively few and taken up by cells within a sphere of only a few millimeters in diameter from their origin particles. The macrophage-induced release of gold ions may continue for years. Injection of gold nanoparticles (nanoGold), on the other hand, is spread throughout the whole body, and the bio-released gold ions, therefore, affect multitudes of cells all over the body, as when using gold-containing drugs such as Myocrisin. Since macrophages and other phagocytotic cells take up and transport nanoGold and remove it after a short period, repeated treatment is necessary. This review describes the details of the cellular mechanisms that lead to the bio-release of gold ions in µGold and nanoGold.

Silver and Hyaluronic Acid-Coated Gold Nanoparticles Modulate the Metabolism of a Model Human Gut Bacterium Lactobacillus casei

Medical applications of nanotechnology are promising in creating efficient and targeted therapies. However, so far, nanodrug design has not taken into consideration possible effects on human microbiota. The beneficial functions of bacteria could be stimulated by nanodrugs while negative effects on beneficial bacteria could cause risks to human health. Here, simulated intestinal fluid (IF) was optimized for culturing a human commensal and probiotic bacterial strain, Lactobacillus casei, to study the effects of medically relevant NPs—Ag and hyaluronic acid-coated Au NPs (HA-Au NPs)—in conditions pertinent to the gastrointestinal tract. When cultivated either aerobically or anaerobically, the specific growth rates of L. casei were ~0.2 h−1 in IF and ~0.4 h−1 in the standard medium of lactobacilli (MRS). Ag NPs inhibited the growth of L. casei in IF at lower concentrations (EC50 ~ 65 and 15 mg/L in aerobic and anaerobic conditions, respectively) than in MRS (EC50 > 100 mg/L), likely caused by differences in the composition of the two media and different intrinsic growth rates of bacteria in IF and MRS. Ag NP dissolution in IF and MRS did not explain the differences in growth inhibition, implying NP-specific effects. HA-Au NPs were not growth-inhibitory to L. casei up to 250 mg/L. Still, both NPs at sub-growth-inhibitory concentrations suppressed the expression of bacteriocin genes in L. casei, suggesting an inhibitory effect of NPs on the probiotic properties of L. casei, i.e., its competitiveness in microbial communities. However, HA-Au NPs did not appear to affect or even stimulated the immunomodulatory properties of L. casei in human intestinal epithelial cells. Thus, medically relevant NPs at low, sub-bacteriostatic levels can affect the metabolism of beneficial human bacteria and potentially induce changes in the microbiota and immune signaling.

Determination of drug efficacy to dissolve cobalt oxide particles in cellular models: Towards a therapeutic approach to decrease pulmonary retention

Following accidental inhalation of radioactive cobalt particles, the poorly soluble and highly radioactive Co₃O₄ particles are retained for long periods in lungs. To decrease their retention time is of crucial importance to minimize radiation-induced damage. As dissolved cobalt is quickly transferred to blood and eliminated by urinary excretion, enhancing the dissolution of particles would favor ⁶⁰Co elimination. We evaluated the ability of ascorbic acid alone or associated with the chelating agents DTPA¹, DFOB² or EDTA³ to enhance dissolution of cobalt particles after macrophage engulfment, and the drug effects on the translocation of the soluble species CoCl₂ through an epithelial barrier. We exposed differentiated THP-1 macrophage-like cells and Calu-3 lung epithelial cells cultured in a bicameral system to cobalt and selected molecules up to 7 days. DTPA, the recommended treatment in man, used alone showed no effect, whereas ascorbic acid significantly increased dissolution of Co₃O₄ particles. An additional efficacy in intracellular particles dissolution was observed for combinations of ascorbic acid with DTPA and EDTA. Except for DFOB, treatments did not significantly modify translocation of dissolved cobalt across the epithelial lung barrier. Our study provides new insights for decorporating strategies following radioactive cobalt particle intake.