Zebrafish embryos of the AB wild-type strain (originally obtained from the Zebrafish International Resource Center, Eugene, Oregon, USA) were raised at 28°C. Zebrafish husbandry, embryo collection, and embryo and larva maintenance were performed as described [20] , [21] . Toxicity assays were standardly performed in 24-well microtiter plates (wrapped with Parafilm to limit solvent evaporation) using 10 embryos per well in 1 ml of 0.3× Danieau's medium (17 mM NaCl, 2 mM KCl, 0.12 mM MgSO4, 1.8 mM Ca(NO3)2 and 1.5 mM HEPES, pH 7.6). Each experiment was repeated 3 times for a total of 30 embryos or larvae analyzed per solvent per developmental staged tested. Data were only recorded for experiments in which the percentage of normal embryos or larvae in the control group was at least 90%. Embryos and larvae were exposed to solvents and carriers at 2–4 cells, 4 hpf, and at 1, 2, 3, 4, and 7 dpf and evaluated for signs of toxicity 24 hours later. In determining the maximum tolerated concentration (MTC) for each solvent and carrier, all post-exposure embryos and larvae were allowed to develop in larva medium to 9 dpf, so as to detect any deleterious effects appearing after this 24-hour window. Solvents and carriers were obtained from the following suppliers: acetone (Chemlab, Zedelgem, Belgium), acetonitrile (Acros Organics, Geel, Belgium), albumin (BSA, Sigma-Aldrich, Bornem, Belgium), butanone (Riedel-de Haën, Seelze, Germany), cyclodextrin (2- hydroxypropyl-beta-cyclodextrin, Sigma-Aldrich), dimethyl formamide (Acros), DMSO (Agros), ethanol (Fisher Scientific, Doornik, Belgium), glycerol (Acros), isopropanol (Chemlab), methanol (Chemlab), polyethylene glycol-400 (Fluka, Bornem, Belgium), propylene glycol (Certa, Eigenbrakel, Belgium), solketal (Merck, Overijse, Belgium). Statistical analyses were done using chi-square in Microsoft Excel.
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