Are bioplastics safe? Hazardous effects of polylactic acid (PLA) nanoplastics in Drosophila

New insights into the reproductive hazards posed by polystyrene nanoplastics

Reproductive toxicity from micro/nanoplastics (MNPLs) is an emerging concern requiring further investigation to close existing knowledge gaps. This study explores the reproductive toxicity of polystyrene nanoplastics (PSNPLs) using Drosophila as an in vivo model. Males and females were exposed to PSNPLs (100 and 500 µg/mL) for one/two weeks. Confocal and transmission electron microscopy revealed widespread distribution of PSNPLs across various tissues, including ovaries, testes, and gametes (ova and sperm). Structural damage, such as hole formation in the seminiferous tubules and ovarian atrophy, was observed following exposure. The physical presence of PSNPLs in reproductive organs disrupted reproductive outcomes, particularly in matings between exposed males and females. Key impairments included reduced fecundity, lower fertility, and a skewed sex ratio, especially after one week of exposure, with minimal effects after two weeks. Significant disruptions in the expression of reproductive and developmental genes were observed in both sexes, with males exhibiting greater sensitivity to PSNPLs, regardless of exposure concentration or duration. These findings provide critical insights into the reproductive toxicity of PSNPLs, underscoring both physical disruptions in reproductive tissues and molecular alterations. This highlights the potential for MNPLs to cause hidden reproductive damage and emphasizes the sex-dependent nature of these toxic effects.

Nanoplastic exposure affects the intestinal microbiota of adult Drosophila flies

Micro- and nanoplastics (MNPLs) are emerging environmental pollutants that have garnered significant attention over the past few decades due to their detrimental effects on human health through various exposure pathways. This study investigates the impact of MNPLs on gut microbiota, utilizing Drosophila melanogaster as a model organism. Drosophila was selected for its microbiota's similarities to humans and its established role as an accessible and well-characterized model system. To analyze microbiota, full-length 16S rRNA gene sequencing was performed using the Nanopore sequencing platform, enabling comprehensive profiling of the microbial populations present in the samples. As models of MNPLs, two commercial polystyrene nanoplastics (PS-NPLs, 61.20 and 415.22 nm) and one lab-made polylactic acid nanoplastic (PLA-NPLs, 463.90 nm) were selected. As a positive control, zinc oxide nanoparticles (ZnO-NPs) were used. The observed findings revealed that exposure to MNPLs induced notable alterations in gut microbiota, including a reduction in bacterial abundance and shifts in species composition. These results suggest that MNPLs exposure can lead to microbial dysbiosis and potential gut health disruptions through its interaction, either with the gut epithelial barrier or directly with the resident microorganisms.

Ecotoxicity of Biodegradable Microplastics and Bio-based Microplastics: A Review of in vitro and in vivo Studies

As biodegradable and bio-based plastics increasingly replace conventional plastics, the need for a comprehensive understanding of their ecotoxicity becomes more pressing. This review systematically presents the ecotoxicity of the microplastics (MPs) from different biodegradable plastics and bioplastics on various animals and plants. High doses of polylactic acid (PLA) MPs (10%) have been found to reduce plant nitrogen content and biomass, and affect the accumulation of heavy metals in plants. Their phytotoxicity becomes more pronounced when blended with polybutylene adipate terephthalate (PBAT) MPs. Polyhydroxybutyrate (PHB) and polybutylene succinate (PBS) MPs show lower phytotoxicity than PLA MPs. At high doses, PLA and PHB MPs may cause dose-dependent developmental toxicity to aquatic organisms. Nano-PLA could induce oxidative stress and genetic damage in insects, indicating its toxicity could be size-dependent and affected by weathering. PBAT MPs have been observed to affect plant growth at lower concentrations (0.1%) than PLA MPs, while polycaprolactone (PCL) affected seed germination only at high temperatures. PCL MPs and extracts could also cause developmental and reproductive toxicity, alter metabolisms, and induce oxidative stress in aquatic organisms at high concentrations. Polypropylene carbonate (PPC) ( > 40 g/kg) MPs have caused earthworm behavioral changes. Non-biodegradable bioplastics are potentially toxic to embryos, larvae, immune systems, reproductive systems, and endocrine systems of animals. However, it is important to note that toxicity studies are still lacking for biodegradable and bio-based plastics, particularly PHB, PBS, PCL, PPC, starch-based, and non-biodegradable bioplastics. More research into the MPs of these plastics is essential to better understand their ecotoxicity and applicability.

Polylactic Acid Micro/Nanoplastic Exposure Induces Male Reproductive Toxicity by Disrupting Spermatogenesis and Mitochondrial Dysfunction in Mice

Although considered an "eco-friendly" biodegradable plastic, polylactic acid (PLA) microplastic (PLA-MP) poses a growing concern for human health, yet its effects on male reproductive function remain underexplored. This study investigated the reproductive toxicity of PLA in male mice and its potential mechanisms. To this end, our in vivo and in vitro experiments demonstrated that after degradation in the digestive system, a significant number of PLA-MP-derived nanoparticles could penetrate the blood-testis barrier (BTB) and localize within the spermatogenic microenvironment. Mice exposed to PLA-MPs for a long time exhibited significant reproductive toxicity, evidenced by decreased sperm concentration and motility, increased sperm deformity rates, and disrupted sex hormone levels. Further analysis revealed that PLA impaired BTB, induced mitochondrial dysfunction in the testes, and triggered oxidative stress through excessive ROS production from mitochondria, leading to further testicular damage. Notably, PLA nanoplastics internalized in the mitochondrial sheath and disrupted the mitochondrial structure of sperm, causing dose-dependent impairments in mitochondrial function. Transcriptome analyses further indicated that PLA-MPs disrupted spermatogenesis by inhibiting the expression of key mRNA involved in this process. Collectively, our findings highlight the reproductive toxic effect of biodegradable PLA by damaging BTB and impairing mitochondrial function, which provides insights into the toxicological implications of biodegradable microplastics for mammalian fertility.

The efficient prediction of inflammatory osteolysis caused by polylactic acid through network toxicology and molecular docking strategy

Polylactic acid (PLA), as a bioplastic, is extensively utilized in bone tissue engineering for its biocompatibility, adaptability and affordability. However, the toxicological research of PLA is still limited. The hydrolysis products of PLA induced inflammatory response which caused inflammatory osteolysis mediated by oxidative damage through the recruitment of macrophages and the accumulation of foreign body multinucleated giant cells, ultimately leading to the failure of bone tissue regeneration. The lack of effective treatments highlights the importance of finding new therapies. This study systematically investigated the potential molecular mechanisms of PLA-induced inflammatory osteolysis by employing network toxicology and molecular docking techniques. We first conducted a network toxicology-based assessment according to the molecular structure of PLA. The result from integrating and screening targets from multiple databases identified 126 potential targets associated with PLA-induced inflammatory osteolysis, and then an interaction network diagram of the targets was constructed. Gene ontology (GO)/KEGG enrichment analysis clarified that PLA may cause inflammatory osteolysis via metabolic pathways and pathways in cancer, as well as lipid and atherosclerosis. Further analysis by STRING and Cytoscape software screened 25 core targets including HSP90AA1, AKT1, SRC, STAT1 and FYN. We found that the enriched highly correlated pathways covered 18 of the 25 core targets, supporting the scientific hypothesis that PLA induces inflammatory osteolysis. Moreover, the results of molecular docking confirmed that PLA displayed a strong binding ability with the core targets and formed stable binding. Taken together, this study not only revealed the potential biological mechanism of PLA-induced inflammatory osteolysis, but also provided new evidence for the future prevention and treatment of PLA-induced inflammation.

Necroecological Trophic Transfer of Microplastics: Insights into the Ecotoxicity of Petroleum-Derived and Biodegradable Polymers

Although the toxicity of petroleum-derived microplastics (MPs) has been widely investigated, the impact of biomicroplastics (BioMPs) remains controversial, and the necroecological trophic transfer of both is still poorly understood. Our study reveals that biomicroplastics may pose ecotoxicological risks comparable to or greater than those of petroleum-derived plastics, a finding that should raise concern. We aimed to evaluate the possible translocation of polystyrene (PS) and polylactic acid (PLA) MPs from mice to the necrophagous fly Synthesiomyia nudiseta and their potential effects on the larval stage. Mice were inoculated intraperitoneally with different doses of MPs [9 (I) and 90 mg/kg (II)] and subjected to the decomposition process (for ten days), allowing colonization by larvae. Our results confirmed the translocation of MPs from mice to S. nudiseta larvae, resulting in a greater accumulation of PLA-MPs compared to PS-MPs. We observed that exposure to MPs significantly influenced biomass accumulation, with larvae from the PS-I and PLA-I groups showing increased biomass. In contrast, those from the PLA-II group exhibited lower biomass. AChE activity was modulated in a concentration-dependent manner, with an increase observed in larvae exposed to PLA-MPs, indicating a potential neurotoxic effect. In addition, there was an increased production of reactive oxygen species (ROS), especially in the groups exposed to higher concentrations of MPs, without a proportional response of antioxidant enzymes, suggesting a redox imbalance and oxidative stress. The elevated serotonin levels and reduced dopamine observed in larvae exposed to MPs indicate a possible redirection of energy resources and changes related to a metabolic adaptation to the stress imposed by MPs. Principal component analysis (PCA) showed that PC1 was strongly influenced by biomarkers such as trypsin, chymotrypsin, AChE, ROS, and dopamine activity, highlighting that PLA-MPs (at the highest concentration) induced more pronounced toxic effects than PS-MPs. This finding was corroborated by discriminant analysis, which revealed a clear separation between the experimental groups, and by multiple regression analysis, which confirmed a strong relationship between MP concentration and larval biomarker responses, indicating that the type and concentration of MPs explained approximately 65% ​​of the variation in the biomarkers evaluated. In conclusion, our study demonstrates for the first time the necroecological trophic translocation of MPs between vertebrates and invertebrates, highlighting the potential risks of biomicroplastics.

Drosophila melanogaster as a tractable eco-environmental model to unravel the toxicity of micro- and nanoplastics

Micro- and nanoplastics have emerged as pervasive environmental pollutants with potential ecotoxicological impacts on various organisms, including the model organismDrosophila melanogaster. Here we comprehensively synthesize current research on the adverse effects of micro- and nanoplastics onDrosophila, highlighting key findings and identifying gaps in the literature. Micro- and nanoplastics can lead to physical damage, oxidative stress, inflammation, genotoxicity, epigenetic changes, apoptosis, and necrosis inDrosophila. Exposure to plastic debris affects nutrient absorption, energy metabolism, and reproductive health, often in a sex-specific manner. For instance, male flies are generally more susceptible to the toxic effects of polystyrene microplastics than female flies, showing greater mortality and metabolic disruptions. Furthermore, the combined exposure of plastics with heavy metals can exacerbate toxic effects, leading to enhanced oxidative stress, genotoxicity, and gut damage. While antagonistic effects have been identified particularly with silver compounds, where polystyrene microplastics reduce the bioavailability and toxicity of silver. The adverse effects of plastic particles onDrosophiladepend on size, with smaller particles penetrating deeper into tissues and eliciting stronger toxic responses. The chemical composition of the plastics and the presence of additives also play crucial roles in determining toxicity levels. Chronic exposure to low levels can be as harmful as acute high-dose exposure, highlighting the need for comprehensive, long-term studies to fully understand the ecological and biological impacts of plastic pollution.

The comparative toxicity of biobased, modified biobased, biodegradable, and petrochemical-based microplastics on the brackish water flea Diaphanosoma celebensis

The escalating production and improper disposal of petrochemical-based plastics have led to a global pollution issue with microplastics (MPs), which pose a significant ecological threat. Biobased and biodegradable plastics are believed to mitigate plastic pollution. However, their environmental fate and toxicity remain poorly understood. This study compares the in vivo effects of different types of MPs, poly(butylene adipate-co-terephthalate) as a biodegradable plastic, polylactic acid (PLA) as a biobased plastic, β-cyclodextrin-grafted PLA as a modified biobased plastic, and low density polyethylene as the reference petrochemical-based plastic, on the key aquatic primary consumer Diaphanosoma celebensis. Exposure to MPs resulted in significant reproductive decline, with comparable effects observed irrespective of MP type or concentration. Exposure to MPs induced distinct responses in redox stress, with transcriptional profiling revealing differential gene expression patterns that indicate varied cellular responses to different types of MPs. ATP-binding cassette transporter activity assays demonstrated altered efflux activity, mainly in response to modified biobased and biodegradable MPs. Overall, this study highlights the comparable in vivo and in vitro effects of biobased, biodegradable, and petrochemical-based MPs on aquatic primary consumers, highlighting their potential ecological implications.

Kinetics and toxicity of nanoplastics in ex vivo exposed human whole blood as a model to understand their impact on human health

The ubiquitous presence of nanoplastics (NPLs) in the environment is considered of great health concern. Due to their size, NPLs can cross both the intestinal and pulmonary barriers and, consequently, their presence in the blood compartment is expected. Understanding the interactions between NPLs and human blood components is required. In this study, to simulate more adequate real exposure conditions, the whole blood of healthy donors was exposed to five different NPLs: three polystyrene NPLs of approximately 50 nm (aminated PS-NH2, carboxylated PS-COOH, and pristine PS- forms), together with two true-to-life NPLs from polyethylene terephthalate (PET) and polylactic acid (PLA) of about 150 nm. Internalization was determined in white blood cells (WBCs) by confocal microscopy, once the different main cell subtypes (monocytes, polymorphonucleated cells, and lymphocytes) were sorted by flow cytometry. Intracellular reactive oxygen species (iROS) induction was determined in WBCs and cytokine release in plasma. In addition, hemolysis, coagulation, and platelet activation were also determined. Results showed a differential uptake between WBC subtypes, with monocytes showing a higher internalization. Regarding iROS, lymphocytes were those with higher levels, which was observed for different NPLs. Changes in cytokine release were also detected, with higher effects observed after PLA- and PS-NH2-NPL exposure. Hemolysis induction was observed after PS- and PS-COOH-NPL exposure, but no effects on platelet functionality were observed after any of the treatments. To our knowledge, this is the first study comprehensively evaluating the bloodstream kinetics and toxicity of NPL from different polymeric types on human whole blood, considering the role played by the cell subtype and the NPLs physicochemical characteristics in the effects observed after the exposures.

In vitro cell-transforming potential of secondary polyethylene terephthalate and polylactic acid nanoplastics

Continuous exposure to plastic pollutants may have serious consequences on human health. However, most toxicity assessments focus on non-environmentally relevant particles and rarely investigate long-term effects such as cancer induction. The present study assessed the carcinogenic potential of two secondary nanoplastics: polyethylene terephthalate (PET) particles generated from plastic bottles, and a biodegradable polylactic acid material, as respective examples of environmentally existing particles and new bioplastics. Pristine polystyrene nanoplastics were also included for comparison. A broad concentration range (6.25-200 μg/mL) of each nanoplastic was tested in both the initiation and promotion conditions of the regulatory assessment-accepted in vitro Bhas 42 cell transformation assay. Parallel cultures allowed confirmation of the efficient cellular internalisation of the three nanoplastics. Cell growth was enhanced by polystyrene in the initiation assay, and by PET in both conditions. Moreover, the number of transformed foci was significantly increased only by the highest PET concentration in the promotion assay, which also showed dose-dependency, indicating that nano PET can act as a non-genotoxic tumour promotor. Together, these findings support the carcinogenic risk assessment of nanoplastics and raise concerns regarding whether real-life co-exposure of PET nanoplastics and other environmental pollutants may result in synergistic transformation capacities.