Teratogenic and neuro-behavioural toxic effects of bisphenol A (BPA) and B (BPB) on Xenopus laevis development

Evaluation of temperature- and ethanol-related developmental degree variations by a new scoring system (FETAX-score) applicable to Frog Embryo Teratogenicity Assay: Xenopus

The aim of the present work is to propose a new quantitative assessment method (FETAX-score) for determining the degree of Xenopus laevis embryo development intended for use in embryotoxicity studies. Inspired by a similar scoring system used to evaluate developmental delays (young-for-age phenotypes) in rat embryos cultured in vitro, the FETAX-score was established by considering seven morphological features (head, naris, mouth, lower jaw, tentacles, intestine, anus) that are easily evaluable in tadpoles during the late stages of development at the conclusion of the test. Given that X. laevis development is temperature-dependent and that temperatures below 14°C and above 26°C are teratogenic, the FETAX-score was tested in embryos maintained at 17, 20, 23 and 26°C. No abnormalities were observed in any group, while the total score was temperature-related, suggesting that the FETAX-score is sensitive to moderate distress that does not influence general morphology. Intestine and anus were the least sensitive structures to temperature variations. To assess the applicability of the FETAX-score in developmental toxicological studies, we evaluated FETAX-score in tadpoles exposed during the morphogenetic period to Ethanol (Eth) at concentrations of 0, 0.25, 0.5, 1, 1.5, and 2 % v/v. Gross malformations were observed only in tadpoles from the Eth 2 % group. By contrast, data analysis of the other Eth groups showed dose-related reductions in the FETAX-score. Tentacles were the most sensitive structures to Eth-related delays. These results support the use of the FETAX-score to quantitatively assess developmental deviations in FETAX embryotoxicity studies.

Effects of combined exposure to two bisphenol plasticizers (BPA and BPB) on Xenopus laevis development

Due to its endocrine disruptive activity, the plastic additive Bisphenol A (BPA) is classified as substance of very high concern (EU ECHA 2017). A correlation between environmental exposure to BPA and congenital defects has been described in humans and in experimental species including the amphibian Xenopus laevis, where severe branchial defects were associated to lethality. The exposure of X. laevis embryos to the BPA analogue bisphenol B (BPB) was recently linked to similar teratogenic effects, with BPB having relative potency about 3 times higher than BPA. The combined BPA-BPB exposure is realistic as both BPA and BPB are detected in human samples and environment. Limited experimental data are available on the combined developmental toxicity of BPA and BPB. The aim of the present work is to evaluate the effects of BPA and BPB mixture in the X. laevis development model, using R-FETAX procedure. The exposure was limited to the first day of development (corresponding to the phylotypic developmental period, common to all vertebrates). Samples were monitored for lethal effects during the full six-day test period and the external morphology was evaluated at the end of the test. Mixture effects were described by modelling, using the PROAST software package. Overall data modelling showed that dose-addiction could not be rejected, suggesting a health concern for co-exposure.

Improved photocatalytic oxidation of micropollutant in wastewater by solar light: assisted palladium-doped graphitic carbon nitride

The escalating global industrial expansion has led to the extensive release of organic compounds into water bodies, resulting in substantial pollution and posing severe threats to both human health and the ecosystem. Among common micropollutants, bisphenol A (MP-BA) has emerged as a significant endocrine-disrupting chemical with potential adverse effects on human health and the environment. This study aims to develop an efficient photocatalyst, specifically by incorporating palladium-doped graphitic carbon nitride (Pd@GCN), to eliminate MP-BA pollutants present in industrial wastewater. The examination of optical properties and photoluminescence indicates that incorporating Pd into GCN enhances the visible light absorption spectra, which extends beyond 570 nm, and accelerates the separation rate of electron-hole pairs. The photocatalytic degradation efficiency of MP-BA increases from 81.7 to 98.8% as the solution pH rises from 5.0 to 9.0. Moreover, Pd@GCN significantly improves the removal rate of MP-BA in wastewater samples, reaching an impressive 92.8% after 60 min of exposure to solar light. Furthermore, the Pd@GCN photocatalyst exhibits notable reusability over six cycles of MP-BA degradation, indicating its promising potential for the treatment of organic pollutants in wastewater under solar light conditions.