Short-term biodistribution and clearance of intravenously administered silica nanoparticles

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Upon IV injection of rats with NM-200, Si mainly accumulates in liver & spleen.

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Silicon concentrations significantly decreased in spleen between 6 and 24 h.

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In liver the same tendency was observed.

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NM-200 has a similar distribution but faster splenic clearance as NM-203.

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Within the first 24 h, silicon was mainly excreted through urine.

Recently, concerns have been raised about potential adverse effects of synthetic amorphous silica, commonly used as food additive (E551), since silica nanoparticles have been detected in food containing E551. We examined the biodistribution and excretion in female Sprague-Dawley rats of NM-200, a well characterized nanostructured silica representative for food applications. A single intravenous injection of NM-200 was applied at a dose of 20 mg/kg_bw, followed by autopsy after 6 and 24 h. The main organs where silicon accumulated were liver and spleen. The silicon concentration significantly decreased in spleen between 6 and 24 h. In liver the tendency was the same but the effect was not significant. This could be due to clearance of the spleen to the liver via the splenic vein, while liver clearance takes more time due to hepatic processing and biliary excretion. In treated animals the liver showed in addition a prominent increase of macrophages between both evaluation moments. Within the first 24 h, silicon was mainly excreted through urine. Further studies are necessary to evaluate the toxicokinetics of different types of silica nanomaterials at lower exposure doses in order to be able to predict kinetics and toxicity of silica nanoparticles depending on their physicochemical characteristics.

Distribution, elimination, and toxicity of silver nanoparticles and silver ions in rats after 28-day oral exposure

We report the results of a 28-day oral exposure study in rats, exposed to <20 nm noncoated, or <15 nm PVP-coated silver nanoparticles ([Ag] = 90 mg/kg body weight (bw)), or AgNO(3) ([Ag] = 9 mg/kg bw), or carrier solution only. Dissection was performed at day 29, and after a wash-out period of 1 or 8 weeks. Silver was present in all examined organs with the highest levels in the liver and spleen for all silver treatments. Silver concentrations in the organs were highly correlated to the amount of Ag(+) in the silver nanoparticle suspension, indicating that mainly Ag(+), and to a much lesser extent silver nanoparticles, passed the intestines in the silver nanoparticle exposed rats. In all groups silver was cleared from most organs after 8 weeks postdosing, but remarkably not from the brain and testis. Using single particle inductively coupled plasma mass spectrometry, silver nanoparticles were detected in silver nanoparticle exposed rats, but, remarkably also in AgNO(3) exposed rats, hereby demonstrating the formation of nanoparticles from Ag(+)in vivo that are probably composed of silver salts. Biochemical markers and antibody levels in blood, lymphocyte proliferation and cytokine release, and NK-cell activity did not reveal hepatotoxicity or immunotoxicity of the silver exposure. In conclusion, oral exposure to silver nanoparticles appears to be very similar to exposure to silver salts. However, the consequences of in vivo formation of silver nanoparticles, and of the long retention of silver in brain and testis should be considered in a risk assessment of silver nanoparticles.

Distribution, elimination, and toxicity of silver nanoparticles and silver ions in rats after 28-day oral exposure

We report the results of a 28-day oral exposure study in rats, exposed to <20 nm noncoated, or <15 nm PVP-coated silver nanoparticles ([Ag] = 90 mg/kg body weight (bw)), or AgNO(3) ([Ag] = 9 mg/kg bw), or carrier solution only. Dissection was performed at day 29, and after a wash-out period of 1 or 8 weeks. Silver was present in all examined organs with the highest levels in the liver and spleen for all silver treatments. Silver concentrations in the organs were highly correlated to the amount of Ag(+) in the silver nanoparticle suspension, indicating that mainly Ag(+), and to a much lesser extent silver nanoparticles, passed the intestines in the silver nanoparticle exposed rats. In all groups silver was cleared from most organs after 8 weeks postdosing, but remarkably not from the brain and testis. Using single particle inductively coupled plasma mass spectrometry, silver nanoparticles were detected in silver nanoparticle exposed rats, but, remarkably also in AgNO(3) exposed rats, hereby demonstrating the formation of nanoparticles from Ag(+)in vivo that are probably composed of silver salts. Biochemical markers and antibody levels in blood, lymphocyte proliferation and cytokine release, and NK-cell activity did not reveal hepatotoxicity or immunotoxicity of the silver exposure. In conclusion, oral exposure to silver nanoparticles appears to be very similar to exposure to silver salts. However, the consequences of in vivo formation of silver nanoparticles, and of the long retention of silver in brain and testis should be considered in a risk assessment of silver nanoparticles.

Quantitative characterization of agglomerates and aggregates of pyrogenic and precipitated amorphous silica nanomaterials by transmission electron microscopy

BACKGROUND

The interaction of a nanomaterial (NM) with a biological system depends not only on the size of its primary particles but also on the size, shape and surface topology of its aggregates and agglomerates. A method based on transmission electron microscopy (TEM), to visualize the NM and on image analysis, to measure detected features quantitatively, was assessed for its capacity to characterize the aggregates and agglomerates of precipitated and pyrogenic synthetic amorphous silicon dioxide (SAS), or silica, NM.

RESULTS

Bright field (BF) TEM combined with systematic random imaging and semi-automatic image analysis allows measuring the properties of SAS NM quantitatively. Automation allows measuring multiple and arithmetically complex parameters simultaneously on high numbers of detected particles. This reduces operator-induced bias and assures a statistically relevant number of measurements, avoiding the tedious repetitive task of manual measurements. Access to multiple parameters further allows selecting the optimal parameter in function of a specific purpose.Using principle component analysis (PCA), twenty-three measured parameters were classified into three classes containing measures for size, shape and surface topology of the NM.

CONCLUSION

The presented method allows a detailed quantitative characterization of NM, like dispersions of precipitated and pyrogenic SAS based on the number-based distributions of their mean diameter, sphericity and shape factor.