Assessing the relevance of in vitro studies in nanotoxicology by examining correlations between in vitro and in vivo data

Abstract

There is an urgent need for in vitro screening assays to evaluate nanoparticle (NP) toxicity. However, the relevance of in vitro assays is still disputable. We administered doses of TiO2 NPs of different sizes to alveolar epithelial cells in vitro and the same NPs by intratracheal instillation in rats in vivo to examine the correlation between in vitro and in vivo responses. The correlations were based on toxicity rankings of NPs after adopting NP surface area as dose metric, and response per unit surface area as response metric. Sizes of the anatase TiO2 NPs ranged from 3 to 100 nm. A cell-free assay for measuring reactive oxygen species (ROS) was used, and lactate dehydrogenase (LDH) release, and protein oxidation induction were the in vitro cellular assays using a rat lung Type I epithelial cell line (R3/1) following 24 hr incubation. The in vivo endpoint was number of PMNs in bronchoalveolar lavage fluid (BALF) after exposure of rats to the NPs via intratracheal instillation. Slope analyses of the dose response curves shows that the in vivo and in vitro responses were well correlated. We conclude that using the approach of steepest slope analysis offers a superior method to correlate in vitro with in vivo results of NP toxicity and for ranking their toxic potency.

Evaluation of Toxicity Ranking for Metal Oxide Nanoparticles via an in Vitro Dosimetry Model

“…The comparative ranking, based on EC 50 calculations, did not show a change in the toxicity ranking by delivered vs administered dose (Figure 6), except for the higher EC 50 for ZnO relative to CuO in RAW264.7 cells. We note, however, that the delivered EC 50 values (10.3 and 12.7 mg/L) for ZnO and CuO differed by only 2.4 mg/L, which falls within the range of experimental uncertainty ( Figure 6).…”

“…However, UVÀvis measurements are affected by the agglomerate size distribution, as well as NP dissolution; thus, such measurements should be regarded as indicative of trends rather than providing precise quantitative measures of the concentration of NPs in suspension. 50 Toxicity Ranking of Metal Oxide NPs per Administered and Delivered Doses. In order to evaluate the impact of metal oxide NP sedimentation on hazard ranking, the validated sedimentation model was applied to the seven metal oxides (Table 1; Figure S3 in the SI) that showed hazard potential ( Figure 4) during the study of a group of 24 NPs.…”

Nanobarcoded superparamagnetic iron oxide nanoparticles for nanomedicine: Quantitative studies of cell–nanoparticle interactions by scanning image cytometry

“…When doses further increase, the doseresponse curve becomes asymptotic as the measured signal becomes saturated. In theory, there is some intermediate dose that induces the "maximal" response, or in other words, the response that is the most sensitive to dose changes (22,23). To determine the maximal response from the SPIONs, it is necessary to test higher masses of SPIONs until a saturation point for each signal is determined.…”

Functionalized nanomaterials: their use as contrast agents in bioimaging: mono- and multimodal approaches

“…It has generally been assumed that in vitro toxicity tests designed for soluble chemicals are appropriate for nanomaterials. However extrapolation of in vitro toxicology findings to humans is not so obvious when the mode of action and/or metabolic conditions in the cell culture model may not be relevant in humans [496][497][498]. This is not an easy task, since the standardized established tests should work for multiple particle types, despite the fact that these NPs have different characteristics and behaviors (fluorescence, magnetism, metallic nature…) but it should definitely be undertaken.…”