Efficacy of the hatching event in assessing the embryo toxicity of the nano-sized TiO2 particles in zebrafish: A comparison between two different classes of hatching-derived variables

The aim of the present study was to evaluate the nano-TiO2 toxicity to zebrafish embryos through evaluating the success in hatching in relationship with hours post-exposure instead of considering just the total hatching rate. Zebrafish embryos 4 h post-fertilization were exposed to nTiO(2) (0, 0.01, 10, and 1000 mu g mL(-1)) for 130 h. The hatching rate (HR) was calculated for each concentration (treatment). The HR magnitude was significantly (p < 0.001) correlated (using simple regression) to hours post-exposure time interval (hpe; 34, 58, 82, 106, and 130), noted as HR.hpe. The HR descriptive statistics (HRds) and the parameters of the regression models (i.e., constant, x, F, and r(2)) were recruited to define 15 HRds- and 4 h. hpe-derived variables, respectively. The efficacy of the variables was evaluated. Exposure to nTiO(2) led to a significant: premature hatching and general decrease in time required for normal hatching: and change in HR and hpe interrelations in a dose-dependent manner. The major change in hatchability between the treatment and control occurred at 58 hpe (62 hpf), when the treatment with nTiO(2) induced significant premature hatching compared to only 6% of the hatched embryos in the control at the same time point. EC10 and EC50 values that cause premature hatching at 58 hpe for nTiO(2) are 0.073 mu g mL(-1) and 107.2 mu g mL(-1) respectively. In general' this study shows multivariate differences among exposure concentrations of nTiO(2) recruiting hatching-derived endpoints. (C) 2015 Elsevier Inc. All rights reserved.