Poly(lactic Acid) Plastics Contamination (plastamination): Size-dependent Effects of Pla-derived Nanoplastics on Early Zebrafish Development

In recent years, attention on plastic pollution has increasingly focused on nanometer-sized particles, known as nanoplastics (NPs). NPs, once released into water habitats, can be ingested by aquatic organisms, leading to various forms of toxicity and posing significant health risks to humans through bioaccumulation along the food chain.1 To limit petroleum-based plastic pollution, biodegradable plastics, namely bioplastics, have been introduced as “green” alternatives with the positive connotation of “environmentally sustainable”.2 However, it is increasingly evident that bioplastics undergo the degradation process, similarly to the fossil-based plastics, producing the ever smaller NPs.2 Nowadays, very little is known about the exposure risk to NPs-derived biodegradable plastics such as the widely used polylactic acid (PLA). Recent data report that its end-products can be internalized at different organ levels and produce toxicity.3 Furthermore, it has been evidenced that the toxic effects may vary based on the effective size of the NPs.1,3 For this reason, in the present study, the main PLA-NPs exposure routes such as ingestion and contact, have been investigated by the in vitro studies on human dermal fibroblasts (HDF) in order to evaluate the PLA-NPs uptake potential, and by the in vivo studies on zebrafish (Danio rerio), to assess the toxic effects on developing organs with a major focus on heart and gut. In particular, HDF and zebrafish embryos and larvae have been exposed to two different sizes and concentrations of PLA NPs up to 120 hpf. The HDF cells showed size-dependent PLA-NPs uptake potential, suggesting their differential ability to bypass the dermal human barrier. The Zebrafish Embryo Acute Toxicity Test evidenced heartbeat rate alterations in all experimental groups, suggesting cardiotoxicity. Morphological alterations were evidenced by histological, histochemical and histomorphometrical analysis. The PLA-NPs demonstrated bioaccumulation in zebrafish in a size- and concentration-dependent manner and was detectable especially in the gastrointestinal tract. In conclusion, it is convincible that the size of the PLA-NPs might influence the amount of internalized NPs and their ability to bypass the biological barriers, exerting further toxic effects on different organ levels. References 1. Trevisan R, et al. Toxics. 2022 Jun 15;10(6):326. doi: 10.3390/toxics10060326.2. Tao, Shiyu et al.” The Science of the total environment vol. 916 (2024): 170299. doi:10.1016/j.scitotenv.2024.170299.3. Zhong, Zhen et al. The Science of the total environment vol. 946 (2024): 174386. doi:10.1016/j.scitotenv.2024.174386.