Development of an analytical method for assessment of silver nanoparticle content in biological matrices by inductively coupled plasma mass spectrometry.

Silver nanoparticles (AgNPs) are a broad class of synthetic nanoparticles that are utilized in a wide variety of consumer products as antimicrobial agents. Despite their widespread use, a detailed understanding of their toxicological characteristics and biological and environmental hazards is not available. To support research into the biodistribution and toxicology of AgNPs, it is necessary to develop a suitable method for the assessment of AgNP content in biological samples. Two methods were developed and validated to analyze citrate-coated AgNP content that utilize acid digestion of rodent feces and liver tissue samples, and a third method was developed for the dilution and direct analysis of rodent urine samples. Following sample preparation, the silver content of each sample was determined by inductively coupled plasma mass spectrometry (ICP-MS) to quantify the silver and AgNP levels present. Analysis of rat feces matrix yielded analytical recoveries ranging from 82 to 93 %. Liver tissue spiked with a formulation of AgNPs over a range of concentrations yielded analytical recoveries between 88 and 90 %, providing acceptable accuracy results. The analysis of silver in urine samples exhibited recovery values ranging from 80 to 85 % for AgNP formulations and 62-84 % for standard silver ion solutions. All determinations exhibited a high degree of analytical precision. The results obtained here suggest that matrix interference plays a minimal role in AgNP recovery in feces and liver tissue, while the urine matrix can exhibit a significant effect on the determination of silver content.

Metabolomics of urine for the assessment of microvesicular lipid accumulation in the liver following isoniazid exposure.

This study was conducted to develop a noninvasive marker of hepatic microvesicular lipid accumulation (MVLA), a histopathological effect currently diagnosed in humans following liver biopsy. MVLA is detected in animal studies of chemicals and drugs and occurs in some humans exposed to chemicals or pharmaceuticals. Because MVLA is a reversible histopathology, early detection of MVLA using a noninvasive method, could aid clinicians in the treatment of patients taking drugs that are known to induce this injury. Isoniazid (INH) was selected as a model compound for this investigation, because MVLA occurs in tuberculosis (TB) patients treated with a combination therapy, which includes INH. This study used male rats dosed daily with INH at 0, 10, or 300 mg/kg/day for up to 8 days. Urine, blood, and liver were obtained following 1 and 8 days. NMR metabolomics of urine revealed markers that correlated (100%) with the findings of MVLA in the right, left, and median liver lobes in 4/9 rats administered the high dose of INH for 8 days. Metabolomics of liver extracts also revealed markers that correlated with the MVLA injury. Serum enzymes that are clinically used to assess liver injury were not consistently correlated to the findings of MVLA. Metabolite changes consistent with the presence of MVLA correlated with interruptions in inositol, carbohydrate, glycerolipid, and glyoxylate metabolism. This study reveals markers that could find pre-clinical use, provides insights into mechanisms involved in MVLA, and demonstrates the need for the validation of noninvasive MVLA markers in human patients.

Metabolomics in the assessment of chemical-induced reproductive and developmental outcomes using non-invasive biological fluids: application to the study of butylbenzyl phthalate.

This study was conducted to evaluate the use of metabolomics for improving our ability to draw correlations between early life exposures and reproductive and/or developmental outcomes. Pregnant CD rats were exposed by gavage daily during gestation to vehicle or to butylbenzyl phthalate (BBP) in vehicle at a level known to induce effects in the offspring and at a level previously not shown to induce effects. Urine was collected for 24 h (on dry ice using all glass metabolism chambers) from dams on gestational day 18 (during exposure) and on post natal day (pnd) 21, and from pnd 25 pups. Traditional phenotypic anchors were measured in pups (between pnd 0 and pnd 26). Metabolomics of urine collected from dams exposed to vehicle or BBP exhibited different patterns for endogenous metabolites. Even three weeks after gestational exposure, metabolic profiles of endogenous compounds in urine could differentiate dams that received the vehicle, low dose or high dose of BBP. Metabolic profiles could differentiate male from female pups, pups born to dams receiving the vehicle, low or high BBP dose, and pups with observable adverse reproductive effects from pups with no observed effects. Metabolites significant to the separation of dose groups and their relationship with effects measured in the study were mapped to biochemical pathways for determining mechanistic relevance. The application of metabolomics to understanding the mechanistic link between low levels of environmental exposure and disease/dysfunction holds huge promise, because this technology is ideal for the analysis of biological fluids in human populations.