This study evaluated the effects of β-diketone antibiotics (DKAs) on the development of embryo-larval zebrafish (Danio rerio). When exposure to DKAs, developmental malformations, such as hatching delay, curved body axis, pericardial edema, uninflated swim bladder and yolk sac edema, were observed at 120 h postfertilization (hpf). The estimated 120 hpf nominal concentrations of no observed effect concentration and lowest observed effect concentration for DKAs were 18.75 and 37.50 mg/L, respectively, suggesting that DKAs have much lower toxicity than other persistent pollutants. Following DKA exposure, embryonic heart rates were significantly reduced as compared to the controls at 48 and 60 hpf. The peak bending motion frequency appeared 1 h earlier than in control embryos. The 2.34 and 9.38-mg/L treatment groups had a higher basal swim rate than control groups at 120 hpf in both light and light-to-dark photoperiod experiments. The occurrence of high speed swim rates was enhanced approximately threefold to sevenfold in the 2.34 and 9.38 mg/L treatments compared to the control. Glutathione (GSH) concentrations in the 2.34 and 9.38-mg/L treatments were significantly higher than the control at 72 hpf, suggesting that GSH production was induced at the end of the hatching period. When exposed to DKAs, zebrafish superoxide dismutase enzyme (SOD) activities were significantly inhibited in the early embryonic period, demonstrating that the clearing ability in zebrafish was lower than the generation rate of free radicals. In summary, the combined DKAs were developmentally toxic to zebrafish in their early life stages and had the ability to impair individual behaviors that are of great importance in the assessment of their ecological fitness.

The interactions between room temperature ionic liquids (RTILs) and weak fluorescent chemicals still remain unclear, which hinders the complete and efficient utilization of these “green” solvents in fluorescent analyses of organic chemicals. Herein, we reported the effects of four RTILs, [C8MIM]BF4, [C14MIM]BF4, [C8MIM]PF6 and [C14MIM]PF6, on fluorescence behavior of 4-tert-octylphenol (4-t-OP). In the fortified concentration range of 0.2–1.0 mM, the quenching effects were increased with increasing concentrations of RTILs. However, no obvious variation of peak shape of 4-t-OP was observed in the quenching process, suggesting no formation of ground-state complex between fluorophores in 4-t-OP and quencher (ionic liquids). As for anion effect, the fluorescence quenching efficiency of 4-t-OP by BF4- was greater than PF6-, but the carbon chain length on the imidazolium ring had no significant relationship with fluorescence intensity of 4-t-OP. Both Ksv values (>1.0 × 103 L/mol.s) and the different temperature effects demonstrated that the quenching of 4-t-OP by four RTILs was the presence of dynamic and static quenching mechanism. The FI of dansyl chloride within [C8MIM]BF4 increased nearly 5-fold as compared to the control, showing a sensitizing effect on the strong fluorescent chemicals, while a quenching effect on 4-t-OP belonging to weak fluorescent chemicals. The fluorescence-enhanced amplitude of dansyl chloride in [C8MIM]PF6 was greater than [C8MIM]BF4. The fluorescence quenching of 4-t-OP by [C8MIM]PF6 did not belong to FRET phenomenon because of no overlap of emission spectrum of 4-t-OP and absorption spectrum of [C8MIM]PF6. When 0.6 mM [C8MIM]PF6 in acetonitrile was used as the solvent, the detection limit of 4-t-OP was 3.7 μg/L, and the linearity range was 0.01–0.8 mg/L (R2 = 0.9990). In summary, these results provide a theoretical foundation for the application of RTILs in weak fluorescent chemicals.

Herein, we report the effects of six different room temperature ionic liquids (RTILs) on fluorescence spectra of 17α-estradiol (EE1) and 17β-estradiol (E2). The selected RTILs belonged to the compound classes of 1-alkyl-3-methylimidazolium tetrafluoroborate ([C(n)MIM]BF(4)) and 1-alkyl-3-methyl imidazolium hexafluorophosphate ([C(n)MIM]PF(6)). RTILs had a gradual quenching effect on fluorescence intensity (FI) of EE1 and E2, and the quenching process followed the well-known Stern-Volmer theory. The quenching mechanism of EE1 and E2 by RTILs was demonstrated to be dynamic quenching. Additionally, the overall quenching efficiency by [C(n)MIM]BF(4) was higher than [C(n)MIM]PF(6). The increased carbon chain length of RTILs did not lead to obvious differences in FI for EE1 and E2. The quenching efficiency showed irregular trend at three different temperatures (25, 35 and 45 °C). RTILs such as [C(4)MIM]PF(6) had the different fluorescent effects on organic chemicals with different fluorophores. The enhancing effects of [C(4)MIM]PF(6) were observed on strong fluorescence chemicals (dansyl chloride, rhrodamine B, 1,10-phenanthroline, norfloxacin), while quenching effect on weak fluorescence chemicals (EE1 and E2). In theory, these results provide a theoretical foundation for deep insight into their interaction mechanism between RTILs and estradiol.

h i g h l i g h t sBoth b-CD and CTAB could sensitize the fluorescence of EE2 and E2. Inclusion ratio of the complex was 1:1. Typical RTILs including [C n MIM]BF 4 and [C n MIM]PF 6 (n = 4, 6). The fluorescence lifetimes were 2.50-2.53 and 4.03-4.13 ns for EE2 and E2. The quenching process was demonstrated to be a dynamic quenching mechanism. g r a p h i c a l a b s t r a c tThe fluorescence lifetimes of EE2 were 2.50 and 4.13 ns, respectively, in water and methanol, and they increased gradually with increasing of b-CD concentrations. a r t i c l e i n f o t r a c tThis study investigated the steady-state and time-resolved fluorescence properties of 17a-ethinylestradiol (EE2) and 17b-estradiol (E2) in the presence of ordered media (b-cyclodextrins (b-CD) and cetyltrimethylammonium bromide (CTAB)). In addition, we analyzed the effects of four room temperature ionic liquids (RTILs) on the fluorescence intensities (FIs) of EE2/b-CD and E2/b-CD inclusion complexes in methanol. Both b-CD and CTAB enhanced the fluorescence of EE2 and E2. The FIs of EE2 and E2 with b-CD or CTAB in methanol were greater than those in water, possibly resulting from decreased oxygen-quenching in H 2 O molecules. b-CD and CTAB may form inclusion complexes with estrogen in both water and methanol. The inclusion ratio of the complex was 1:1 and the inclusion constant (K) values in water were greater than those in methanol. The fluorescence lifetimes were 2.50 and 4.13 ns for EE2 and 2.58 and 4.03 ns for E2 in aqueous solution and methanol, respectively. The changing trend of fluorescence lifetimes for EE2 and E2 in b-CD or CTAB was similar to the steady-state FIs. The four RTILs had a significant quenching effect on the FIs of EE2/b-CD and E2/b-CD, and the quenching process for EE2/ b-CD and E2/b-CD by RTILs was demonstrated to be a dynamic quenching mechanism. Fluorescent data obtained from these complex systems provide a theoretical foundation for understanding the interaction mechanisms between ordered media and RTILs in the analysis of estrogens.