The role of response-metric in nanoparticle toxicology

• Main Author: Han, Xianglu
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2009
• Subjects: Nanoscience; Nanotechnology; Surgery
• ISBN: 9781109695366; 1109695365

With the increasing number and variety of NPs and the current dispute regarding the value of in vitro assays in predicting in vivo toxicity of NPs, there is an urgent need for developing and validating screening assays that work well for evaluating nanoparticle (NP) toxicity. To test the overall hypothesis that results of in vitro assays can be used to predict acute in vivo effects and to establish a hazard scale based on careful analysis of the dose-response curve using appropriate response metric, we evaluated the usefulness of several assays by adopting NP surface area as the dose metric and a response metric that is based on surface area. Several anatase TiO2 NPs (of sizes from 3 to 100 nm) were examined for this purpose. In addition to in vitro studies where a cell-free assay and several cellular assays based on a rat lung Type I epithelial cell line (R3/1) were used, we examined pulmonary inflammation or cytotoxicity related in vivo endpoints following exposure of rats to the NPs via intratracheal instillation. For the correlation studies, in vitro endpoints included ROS generation in a cell-free system, lactate dehydrogenase (LDH) release from R3/1 cells, and protein carbonylation in R3/1 cells; the in vivo endpoint was the number of neutrophils (i.e., polymorphonuclear leukocytes, PMNs) in bronchoalveolar lavage fluid (BALF) following intratracheal instillation. In addition, using several other types of NPs (a titanium dioxide NP P-25, a copper, and two silver NPs), the LDH assay was evaluated via LDH inactivation studies in different media with or without the presence of NPs and via several other experiments such as oxidation of NADH by NPs. We found that most of the NPs we studied (except a copper NP and a carbon-containing silver NP) did not cause a significant interference with the assay. Protein carbonylation was a good marker for oxidative stress related toxicity for most of the NPs except silver particles. The in vitro and in vivo data were well correlated when using the steepest slopes in the dose-response curves for correlation analysis and when using surface area as the basis for dose- and response-metrics, suggesting that proper dose- and response-metrics are important for evaluating in vivo—in vitro correlations. We conclude that toxicity rankings based on certain in vitro assays reflect well the in vivo toxicity rankings when proper dose and response metrics were utilized. This work points the way to developing models for predicting in vivo toxicity of NPs based on data from validated in vitro screening assays. Such correlation and prediction studies will be increasingly important for rapid screening of NP toxicity via the development and validation of high-throughput in vitro assays. Such an effort will be as promising as, if not more promising than, quantitative structure-activity relationship (QSAR) techniques that are being assessed by several research groups for predicting NP toxicity based on complex physicochemical properties of NPs.