Fate and impact of nanoplastics in the human digestive environment after oral exposure: A common challenge for toxicology and chemistry

Impacts of polystyrene nanoplastics on zebrafish gut microbiota and mechanistic insights

Aquatic environments are frequently contaminated with nanoplastics (NPs) ranging from 1-100 nm generated by plastic aging, but their bio-enrichment and toxicological impacts remain poorly understood. This study investigates how chronic exposure to carboxylated polystyrene nanoplastics (PNPs) alters gut microbiota composition and function in zebrafish (Danio rerio). Adult zebrafish were exposed to 50 nm PNPs at concentrations of 0.1, 1.0, and 10 mg/L for 14 and 28 days, followed by gut microbiota analysis using 16S rRNA gene sequencing. PNP exposure altered gut microbiota composition, including an increase in Proteobacteria abundance and a decrease in Firmicutes, Bacteroidetes, and the inflammation-related genus Alistipes. Beneficial probiotics such as Faecalibacterium, Streptococcus, Bifidobacterium, and Lachnospira were diminished, while pathogenic bacteria proliferated. TEM imaging revealed the internalization of PNP particles within intestinal tissues resulted in vacuolation, suggesting potential epithelial damage. Co-occurrence network patterns of gut microbiota greatly decreased during treatment with NPs. The neutral community model showed that among PNP treatments, 0.1 mg/L led to a less predictable (stochastic assembly process). PNP exposure led to increased predicted microbial functions (via PICRUSt2) related to xenobiotic metabolism, infection pathways, and lipopolysaccharide (LPS) production, while RNA transport and N-glycan biosynthesis were decreased. However, pathways related to microbial antioxidants exhibited significant variation across different PNP levels. These results provide critical insights into the toxicological impacts of chronic PNP exposure on fish gut health, highlighting the potential risks to aquatic ecosystems and human health.

Degradation of Polymer Materials in the Environment and Its Impact on the Health of Experimental Animals: A Review

The extensive use of polymeric materials has resulted in significant environmental pollution, prompting the need for a deeper understanding of their degradation processes and impacts. This review provides a comprehensive analysis of the degradation of polymeric materials in the environment and their impact on the health of experimental animals. It identifies common polymers, delineates their degradation pathways, and describes the resulting products under different environmental conditions. The review covers physical, chemical, and biological degradation mechanisms, highlighting the complex interplay of factors influencing these processes. Furthermore, it examines the health implications of degradation products, using experimental animals as proxies for assessing potential risks to human health. By synthesizing current research, the review focuses on studies related to small organisms (primarily rodents and invertebrates, supplemented by fish and mollusks) to explore the effects of polymer materials on living organisms and underscores the urgency of developing and implementing effective polymer waste management strategies. These strategies are crucial for mitigating the adverse environmental and health impacts of polymer degradation, thus promoting a more sustainable interaction between human activities and the natural environment.

What if you eat nanoplastics? Simulating nanoplastics fate during gastrointestinal digestion

Despite our growing awareness of micro-and nanoplastics presence in food and beverages, the fate of nanoplastics (NPs) in the human gastrointestinal tract (GIT) remains poorly investigated. Changes of nanoplastics size upon digestive conditions influence the potential of absorption through the intestine. In this study, polymer nanoparticles with different physicochemical properties (size, surface and chemistry) were submitted to gastrointestinal digestion (GID) simulated in vitro. Their agglomeration behaviour was measured with a unique set of analytical approaches, allowing to study NPs' interactions with the digestive enzymes. Smaller NPs agglomerated more, narrowing the overall particle size distribution of smaller and larger NPs. NPs of different polymers exhibited heteroagglomeration. Digestive enzymes interact with the NPs, forming large but fragile agglomerates. In presence of the enzymes, even acid-functionalized NPs, typically stable in harsh conditions, agglomerated similarly to the non-functionalized PS NPs. These results highlight the role of the GID in increasing the effective size of ingested NPs, potentially reducing their ability to pass through the cell membranes. Our findings address a critical knowledge gap in nanoplastics oral uptake potential, providing a solid technical foundation for their characterization.