Transcriptomic Responses of Zebrafish Embryos to Sublethal Exposure of Natural Biopolymers (BP) and Naturally Modified Polymers (NMP): A 96-Hour RNA-Seq Analysis

This research provides a thorough ecotoxicological evaluation of natural biopolymers (BP) and naturally modified polymers (NMP). The study focuses on biopolymers such as chitosan, xanthan, alginate, and carboxymethyl cellulose (CMC), alongside NMPs like Jelucel HM 200 and Emwaxy Jel 100. Each polymer was individually tested on zebrafish embryos using a zebrafish embryo toxicity (zFET) test. Natural polymers, although prevalent in agrotechnical products, remain largely unregulated under REACH due to their natural origins. There is a critical lack of data regarding their potential impact on closed ecosystem cycles, raising concerns about environmental risks. To assess the sublethal effects of these polymers, a modified zebrafish embryo toxicity test (ZFET) was utilized, incorporating transcriptomics as an additional evaluation endpoint. This modified methodology adheres to the OECD 236 guidelines but includes specific adjustments for gene expression analysis, such as changes in the number of embryos used, test setup volume, and sample processing procedures. Zebrafish embryos were exposed for 96 hours to each polymer's filtrate at a maximum concentration of 100 mg/L. After exposure, the embryos underwent assessments for survival rates, hatching rates, and morphological malformations. The study identified differentially expressed genes (DEGs) for each polymer exposure, shedding light on the transcriptomic changes induced by both biopolymers and NMPs. The primary objective is to understand how these substances influence gene expression profiles in zebrafish embryos, aiming to identify transcriptomic biomarkers that could assist in environmental risk assessment. This research contributes valuable insights into the potential ecological impacts of natural and modified polymers, highlighting the need for further regulatory consideration.