Simulated gastrointestinal digestion of polylactic acid (PLA) biodegradable microplastics and their interaction with the gut microbiota

Comparative evaluation of biodegradable microplastic presence in edible and non-edible tissues of cage-cultured and wild fishes of Periyar River

Biodegradable plastics (BPs) are considered a promising alternative to conventional plastics; however, their biodegradation necessitates specific conditions and can persist in the environment for extended periods, posing toxicological effects on aquatic ecosystems and their organisms similar to conventional microplastics. The studies on biodegradable microplastics (BMPs) are limited and therefore, this study, aimed to evaluate the BMP presence in the gastrointestinal tract (GIT) and edible tissues of wild-caught and cage-cultured fishes of Periyar River, Kerala, India. Etroplus suratensis (n = 300) and Oreochromis mossambicus (n = 300) were collected from both sources. The study found BMPs in the GIT of all fishes sourced from cages and wild, with a higher but statistically insignificant abundance in wild fishes: 0.06 ± 0.26 items/individual (0.01 ± 0.00 items/g) in E. suratensis and 0.03 ± 0.23 items/individual (0.01 ± 0.01 items/g) in O. mossambicus. No BMPs were found in the edible tissues of cage-cultured fish, but they were detected in wild-caught fishes, i.e., 0.02 ± 0.13 items/individual (0.02± 0.01 items/g) in E. suratensis and 0.01 ± 0.11 items/individual (0.02± 0.01 items/g) in O. mossambicus. Poly (butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA) were the only BMPs obtained in fish from both sources with the former being the dominant one. The potential annual average human exposure risk from the wild-caught fish was estimated from both fish species and the findings suggest children have a higher risk of exposure, i.e., 551 items/year followed by adults, i.e., 394 items/year and aged individuals, i.e., 239 items/year. The documented harmful impacts of BMPs on aquatic organisms, combined with the findings of this study, suggest the need for a thorough reassessment of BP production and disposal practices. Additionally, implementing robust monitoring systems is essential to food safety and public health.

Eco-friendly or eco-threat? Influence of feeding zone on biodegradable microplastic uptake in freshwater fish and its impact on environment and food safety

Biodegradable plastics (BPs) are considered a sustainable alternative to reduce the long-term plastic pollution. However, recent research indicates that the degradation time of BPs varies depending on several factors, and biodegradable microplastics (BMPs) exhibit toxicological effects comparable to those of conventional microplastics, raising concerns about their use. There is a significant lack of research on the factors affecting BMP uptake in fish, with some studies focusing on the effects of BMPs under controlled laboratory settings. This study, the first of its kind in India, aims to examine the uptake of BMPs in freshwater fish from different feeding zones-pelagic, benthopelagic, and demersal-of the Periyar River in Kerala, India. Xenentodon cancila (pelagic; n = 80), Etroplus suratensis (benthopelagic; n = 80) and Anabas testudineus (demersal; n = 80) were selected for the study. The gastrointestinal tract (GIT) and edible tissues were isolated and analysed. BMPs were observed in the following order: benthopelagic > demersal> pelagic. Highest mean BMP abundance was recorded in E. suratensis (benthopelagic) i.e. 0.24±0.05 items/individual (0.04±0.01 items/g) in GIT and 0.08±0.03 items/individual (0.002± 0.00 items/g) in edible tissues. Poly (butylene adipate-co-terephthalate) (PBAT) was the only polymer observed. Adults have a comparatively higher risk of BMP exposure from E. suratensis and A. testudineus than children and aged individuals. The presence of BMPs in freshwater fish collected from the three feeding zones indicates widespread contamination across diverse habitats. This finding suggests that BMPs, despite their biodegradable nature, persist in aquatic environments long enough to enter the food web and is a growing environmental concern that must be addressed and appropriate strategies should be made to align with the goals of reducing pollution and protecting ecosystems.

Exploring Environmental Behaviors and Health Impacts of Biodegradable Microplastics

Biodegradable plastics (BPs) are promoted as eco-friendly alternatives to conventional plastics. However, compared to conventional microplastics (MPs), they degrade rapidly into biodegradable microplastics (BMPs), which may lead to a more significant accumulation of BMPs in the environment. This review systematically compares BMPs and MPs, summarizes current knowledge on their environmental behaviors and impacts on ecosystems and human health, and offers recommendations for future research. BMPs are detected in water, sediments, indoor dust, food, marine organisms, and human samples. Compared to MPs, BMPs are more prone to environmental transformations, such as photodegradation and biodegradation, which results in a shorter migration distance across different matrices. Like MPs, BMPs can adsorb pollutants and transport them into organisms, enhancing toxicity and health risks through the Trojan horse effect. Studies indicate that BMPs may negatively impact terrestrial and aquatic ecosystems more than MPs by disrupting nutrient cycling and inhibiting plant and animal growth. In vivo and in vitro research also shows that BMP degradation products increase bioavailability, exacerbating neurotoxicity and overall toxicity. However, findings on BMPs' environmental and health effects remain inconsistent. Further evaluation of the trade-offs between BMP risks and their biodegradability is needed to address these uncertainties.

Quantitative tracking of the transformation of micro- and nanoplastics in simulated human body fluid

Micro- and nanoplastics (MNPs) are widespread in the environment and food, posing ingestion risks through various pathways. However, their transformation in human body fluids (SBFs), especially the formation of secondary nanoparticles (NPs), is not well understood due to inadequate quantification methods. This study proposed a robust method for quantifying eight common MNPs using pressurized liquid extraction (PLE) for pretreatment and pyrolysis gas chromatography-quadrupole time-of-flight mass spectrometry (Py-GC-QTOF-MS) for analysis. The method demonstrated high performance with recoveries over 90.9 % and a detection limit down to 0.01 mg/L. Most sample matrices did not interfere with MNP quantification, though poly(3-hydroxybutyrate) and polyethylene required background noise deduction. High recoveries in SBFs (>79.0 %) further confirmed the practicality of this method. Utilizing this method, it was found that only a few MPs were able to release secondary NPs within the simulated digestive system, with the maximum proportion of released NPs less than 2.1 %, suggesting a negligible health risk from secondary NPs. Besides, ester structure was found not to promote the formation of secondary NPs but did affect surface morphology and functional groups to a certain extent. We anticipate that this work will open opportunities for the health risk assessment of MNPs.

Lactic acid bacteria reduce polystyrene micro- and nanoplastics-induced toxicity through their bio-binding capacity and gut environment repair ability

Microplastics and nanoplastics (MNPs) are emerging environmental contaminants that have received significant attention in recent years. Currently, there are more studies on the toxic effects of MNPs exposure on animals (especially aquatic organisms and mammals), but data on the reduction of toxic effects caused by MNPs exposure are still very limited. Lactic acid bacteria (LAB), recognized as safe food-grade microorganisms, possess the capability to bioconjugate harmful substances. In this experiment, we chose lactic acid bacteria (LAB) with different binding capacities to MNPs in vitro to intervene in MNPs-exposed mice to investigate the reducing effect on the toxicity caused by MNPs exposure. Our study showed that LAB with a high intercalation capacity with MNPs in vitro were more effective in alleviating the toxicity caused by MNPs exposure. Notably, Lactobacillus plantarum DT22, despite its low inter-adsorption with MNPs, played a pivotal role in upregulating the relative expression of tight junction proteins and modulating the intestinal microbiota. Thus, LAB strains' mitigation of MNPs toxicity extends beyond bio-binding; their capacity to repair the damaged gut environment is also crucial. LAB strains are proposed as a dietary intervention to reduce MNPs-induced toxicity.

The microplastic-crisis: Role of bacteria in fighting microplastic-effects in the digestive system

Plastic particles smaller than 5 mm, referred to as Microplastics, pose health risks, like metabolic, immunological, neurological, reproductive, and carcinogenic effects, after being ingested. Smaller plastic particles are more likely to be absorbed by human cells, with nanoplastics showing higher potential for cellular damage, including DNA fragmentation and altered protein functions. Micro- and nanoplastics (MNPs) affect the gastrointestinal tract by altering the microbial composition, they could influence digestive enzymes, and possibly disrupt mucus layers. In the stomach, they potentially interfere with digestion and barrier functions, while in the intestines, they could increase permeability via inflammation and tissue disruption. MNPs can lead to microbial dysbiosis, leading to gastrointestinal symptoms. By activating inflammatory pathways, altering T cell functions and affecting dendritic cells and macrophages, immune system homeostasis could possibly be disrupted. Probiotics offer potential strategies to alleviate plastic effects, by either degrading plastic particles or directly countering health effects. We compared genetic sequences of probiotics to the genome of known plastic degraders and concluded that no probiotic bacteria could serve the role of plastic degradation. However, probiotics could directly mitigate MNP-health effects. They can restore microbial diversity, enhance the gut barrier, regulate bile acid metabolism, reduce inflammation, regulate insulin balance, and counteract metabolic disruptions. Antioxidative properties protect against lipid peroxidation and MNP-related reproductive system damage. Probiotics can also bind and degrade toxins, like heavy metals and bisphenol A. Additionally, bacteria could be used to aggregate MNPs and reduce their impact. Therefore, probiotics offer a variety of strategies to counter MNP-induced health effects.

Polyvinyl chloride (PVC), its additives, microplastic and human health: Unresolved and emerging issues

Polyvinyl chloride (PVC), a commonly used plastic across Europe, poses a number of risks at various stages of its life cycle. The carcinogenicity of PVC monomer, the need to use high number and volume of problematic additives, the easiness of fragmentation compared to other thermoplastics, the high volume of use in everyday products and the resulting extent to which European population is potentially exposed to both microplastics and chemicals and, finally, continuous problems during waste management, have raised concerns about impacts of PVC on human health and the environment for decades. As far back as in 2000, the European Commission recognized that PVC causes a wide range of serious problems for the environment and human health. More recently, in April 2022, PVC and its additives were included in the European Union's Restrictions Roadmap, and the European Chemicals Agency's investigation ruled that, to limit the use of some additives and to minimize releases of PVC microparticles, regulatory action would be necessary. Additionally, the Global Plastics Treaty discussions emphasise a need to ensure that plastics that remain in the economy are free of hazardous chemicals, including hazardous polymers. In this paper, we reviewed the available data on PVC microplastic, additives, the end of life options of products made of PVC, and how they all are connected. It is crucial to consider this polymer within the broader context of chemical pollution and circular economy, acknowledging that changes in how we manage our resources are necessary to achieve the goal for a truly non-toxic environment in the future.

Advances in bio-polymer coatings for probiotic microencapsulation: chitosan and beyond for enhanced stability and controlled release

This review paper analyzes recent advancements in bio-polymer coatings for probiotic microencapsulation, with a particular emphasis on chitosan and its synergistic combinations with other materials. Probiotic microencapsulation is essential for protecting probiotics from environmental stresses, enhancing their stability, and ensuring effective delivery to the gut. The review begins with an overview of probiotic microencapsulation, highlighting its significance in safeguarding probiotics through processing, storage, and gastrointestinal transit. Advances in chitosan-based encapsulation are explored, including the integration of chitosan with other bio-polymers such as alginate, gelatin, and pectin, as well as the application of nanotechnology and innovative encapsulation techniques like spray drying and layer-by-layer assembly. Detailed mechanistic insights are integrated, illustrating how chitosan influences gut microbiota by promoting beneficial bacteria and suppressing pathogens, thus enhancing its role as a prebiotic or synbiotic. Furthermore, the review delves into chitosan's immunomodulatory effects, particularly in the context of inflammatory bowel disease (IBD) and autoimmune diseases, describing the immune signaling pathways influenced by chitosan and linking gut microbiota changes to improvements in systemic immunity. Recent clinical trials and human studies assessing the efficacy of chitosan-coated probiotics are presented, alongside a discussion of practical applications and a comparison of in vitro and in vivo findings to highlight real-world relevance. The sustainability of chitosan sources and their environmental impact are addressed, along with the novel concept of chitosan's role in the gut-brain axis. Finally, the review emphasizes future research needs, including the development of personalized probiotic therapies and the exploration of novel bio-polymers and encapsulation techniques.

Current trends in 3D printed gastroretentive floating drug delivery systems: A comprehensive review

Gastrointestinal (GI) environment is influenced by several factors (gender, genetics, sex, disease state, food) leading to oral drug absorption variability or to low bioavailability. In this scenario, gastroretentive drug delivery systems (GRDDS) have been developed in order to solve absorption problems, to lead to a more effective local therapy or to allow sustained drug release during a longer time period than the typical oral sustained release dosage forms. Among all GRDDS, floating systems seem to provide a promising and practical approach for achieving a long intra-gastric residence time and sustained release profile. In the last years, a novel technique is being used to manufacture this kind of systems: three-dimensional (3D) printing technology. This technique provides a versatile and easy process to manufacture personalized drug delivery systems. This work presents a systematic review of the main 3D printing based designs proposed up to date to manufacture floating systems. We have also summarized the most important parameters involved in buoyancy and sustained release of the systems, in order to facilitate the scale up of this technology to industrial level. Finally, a section discussing about the influence of materials in drug release, their biocompatibility and safety considerations have been included.

Compounding one problem with another? A look at biodegradable microplastics

Environmental concerns about microplastics (MPs) have motivated research of their sources, occurrence, and fate in aquatic and soil ecosystems. To mitigate the environmental impact of MPs, biodegradable plastics are designed to naturally decompose, thus reducing the amount of environmental plastic contamination. However, the environmental fate of biodegradable plastics and the products of their incomplete biodegradation, especially micro-biodegradable plastics (MBPs), remains largely unexplored. This comprehensive review aims to assess the risks of unintended consequences associated with the introduction of biodegradable plastics into the environment, namely, whether the incomplete mineralization of biodegradable plastics could enhance the risk of MBPs formation and thus, exacerbate the problem of their environmental dispersion, representing a potentially additional environmental hazard due to their presumed ecotoxicity. Initial evidence points towards the potential for incomplete mineralization of biodegradable plastics under both controlled and uncontrolled conditions. Rapid degradation of PLA in thermophilic industrial composting contrasts with the degradation below 50 % of other biodegradables, suggesting MBPs released into the environment through compost. Moreover, degradation rates of <60 % in anaerobic digestion for polymers other than PLA and PHAs suggest a heightened risk of MBPs in digestate, risking their spread into soil and water. This could increase MBPs and adsorbed pollutants' mobilization. The exact behavior and impacts of additive leachates from faster-degrading plastics remain largely unknown. Thus, assessing the environmental fate and impacts of MBPs-laden by-products like compost or digestate is crucial. Moreover, the ecotoxicological consequences of shifting from conventional plastics to biodegradable ones are highly uncertain, as there is insufficient evidence to claim that MBPs have a milder effect on ecosystem health. Indeed, literature shows that the impact may be worse depending on the exposed species, polymer type, and the ecosystem complexity.

Single exposure of food-derived polyethylene and polystyrene microplastics profoundly affects gut microbiome in an in vitro colon model

Microplastics (MPs) are widespread contaminants highly persistent in the environment and present in matrices to which humans are extensively exposed, including food and beverages. MP ingestion occurs in adults and children and is becoming an emerging public health issue. The gastrointestinal system is the most exposed to MP contamination, which can alter its physiology starting from changes in the microbiome. This study investigates by an omic approach the impact of a single intake of a mixture of polyethylene (PE) and polystyrene (PS) MPs on the ecology and metabolic activity of the colon microbiota of healthy volunteers, in an in vitro intestinal model. PE and PS MPs were pooled together in a homogeneous mix, digested with the INFOGEST system, and fermented with MICODE (multi-unit in vitro colon model) at loads that by literature correspond to the possible intake of food-derived MPs of a single meal. Results demonstrated that MPs induced an opportunistic bacteria overgrowth (Enterobacteriaceae, Desulfovibrio spp., Clostridium group I and Atopobium - Collinsella group) and a contextual reduction on abundances of all the beneficial taxa analyzed, with the sole exception of Lactobacillales. This microbiota shift was consistent with the changes recorded in the bacterial metabolic activity.

The triple exposure nexus of microplastic particles, plastic-associated chemicals, and environmental pollutants from a human health perspective

The presence of microplastics (MPs) is increasing at a dramatic rate globally, posing risks for exposure and subsequent potential adverse effects on human health. Apart from being physical objects, MP particles contain thousands of plastic-associated chemicals (i.e., monomers, chemical additives, and non-intentionally added substances) captured within the polymer matrix. These chemicals are often migrating from MPs and can be found in various environmental matrices and human food chains; increasing the risks for exposure and health effects. In addition to the physical and chemical attributes of MPs, plastic surfaces effectively bind exogenous chemicals, including environmental pollutants (e.g., heavy metals, persistent organic pollutants). Therefore, MPs can act as vectors of environmental pollution across air, drinking water, and food, further amplifying health risks posed by MP exposure. Critically, fragmentation of plastics in the environment increases the risk for interactions with cells, increases the presence of available surfaces to leach plastic-associated chemicals, and adsorb and transfer environmental pollutants. Hence, this review proposes the so-called triple exposure nexus approach to comprehensively map existing knowledge on interconnected health effects of MP particles, plastic-associated chemicals, and environmental pollutants. Based on the available data, there is a large knowledge gap in regard to the interactions and cumulative health effects of the triple exposure nexus. Each component of the triple nexus is known to induce genotoxicity, inflammation, and endocrine disruption, but knowledge about long-term and inter-individual health effects is lacking. Furthermore, MPs are not readily excreted from organisms after ingestion and they have been found accumulated in human blood, cardiac tissue, placenta, etc. Even though the number of studies on MPs-associated health impacts is increasing rapidly, this review underscores that there is a pressing necessity to achieve an integrated assessment of MPs' effects on human health in order to address existing and future knowledge gaps.

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

The expanded uses of bioplastics require understanding the potential health risks associated with their exposure. To address this issue, Drosophila melanogaster as a versatile terrestrial in vivo model was employed, and polylactic acid nanoplastics (PLA-NPLs), as a proxy for bioplastics, were tested as a material model. Effects were determined in larvae exposed for 4 days to different concentrations (25, 100, and 400 μg/mL) of 463.9 ± 129.4 nm PLA-NPLs. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) approaches permitted the detection of PLA-NPLs in the midgut lumen of Drosophila larvae, interacting with symbiotic bacteria. Enzymatic vacuoles were observed as carriers, collecting PLA-NPLs and enabling the crossing of the peritrophic membrane, finally internalizing into enterocytes. Although no toxic effects were observed in egg-to-adult survival, cell uptake of PLA-NPLs causes cytological disturbances and the formation of large vacuoles. The translocation across the intestinal barrier was demonstrated by their presence in the hemolymph. PLA-NPL exposure triggered intestinal damage, oxidative stress, DNA damage, and inflammation responses, as evaluated via a wide set of marker genes. Collectively, these structural and molecular interferences caused by PLA-NPLs generated high levels of oxidative stress and DNA damage in the hemocytes of Drosophila larvae. The observed effects point out the need for further studies aiming to deepen the health risks of bioplastics before adopting their uses as a safe plastic alternative.

Revealing the environmental hazard posed by biodegradable microplastics in aquatic ecosystems: An investigation of polylactic acid's effects on Microcystis aeruginosa

The influence of petroleum-based microplastics (MPs) on phytoplankton has been extensively studied, while research on the impact of biodegradable MPs, derived from alternative plastics to contest the environmental crisis, remains limited. This study performed a 63 days co-incubation experiment to assess the effect of polylactic acid MPs (PLA-MPs) on the growth, physiology, and carbon utilization of M. aeruginosa and the change in PLA-MPs surface properties. The results showed that despite PLA-MPs induced oxidative stress and caused membrane damage in M. aeruginosa, the presence of PLA-MPs (10, 50, and 200 mg/L) triggered significant increases (p < 0.05) in the density of M. aeruginosa after 63 days. Specifically, the algal densities upon 50 and 200 mg/L PLA-MPs exposure were increased by 20.91% and 36.31% relative to the control, respectively. Meanhwhile, the reduced C/O ratio on PLA-MPs surface and change in PLA-MPs morphological characterization, which is responsible for substantially increase in the aquatic dissolved inorganic carbon concentration during the co-incubation, implying the degradation of PLA-MPs; thus, provided sufficient carbon resources that M. aeruginosa could assimilate. This was in line with the declined intracellular carbonic anhydrase content in M. aeruginosa. This study is the first attempt to uncover the interaction between PLA-MPs and M. aeruginosa, and the finding that their interaction promotes the degrading of PLA-MPs meanwhile favoring M. aeruginosa growth will help elucidate the potential risk of biodegradable MPs in aquatic environment.

Microplastics alter soil structure and microbial community composition

Microplastics (MPs), including conventional hard-to-biodegrade petroleum-based and faster biodegradable plant-based ones, impact soil structure and microbiota in turn affecting the biodiversity and functions of terrestrial ecosystems. Herein, we investigated the effects of conventional and biodegradable MPs on aggregate distribution and microbial community composition in microhabitats at the aggregate scale. Two MP types (polyethylene (PE) and polylactic acid (PLA) with increasing size (50, 150, and 300 μm)) were mixed with a silty loam soil (0-20 cm) at a ratio of 0.5 % (w/w) in a rice-wheat rotation system in a greenhouse under 25 °C for one year. The effects on aggregation, bacterial communities and their co-occurrence networks were investigated as a function of MP aggregate size. Conventional and biodegradable MPs generally had similar effects on soil aggregation and bacterial communities. They increased the proportion of microaggregates from 17 % to 32 %, while reducing the macroaggregates from 84 % to 68 %. The aggregate stability decreased from 1.4 mm to 1.0-1.1 mm independently of MP size due to the decline in the binding agents gluing soil particles (e.g., microbial byproducts and proteinaceous substances). MP type and amount strongly affected the bacterial community structure, accounting for 54 % of the variance. Due to less bioavailable organics, bacterial community composition within microaggregates was more sensitive to MPs addition compared to macroaggregates. Co-occurrence network analysis revealed that MPs exacerbated competition among bacteria and increased the complexity of bacterial networks. Such effects were stronger for PE than PLA MPs due to the higher persistence of PE in soils. Proteobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, and Gemmatimonadetes were the keystone taxa in macroaggregates, while Actinobacteria and Chloroflexi were the keystone taxa in microaggregates. Proteobacteria, Actinobacteria, and Chloroflexi were the most sensitive bacteria to MPs addition. Overall, both conventional and biodegradable MPs reduced the portion of large and stable aggregates, altering bacterial community structures and keystone taxa, and consequently, the functions.

Critical aspects in dissolution testing of nanomaterials in the oro-gastrointestinal tract: the relevance of juice composition for hazard identification and grouping

The dissolution of a nanomaterial (NM) in an in vitro simulant of the oro-gastrointestinal (OGI) tract is an important predictor of its biodurability in vivo. The cascade addition of simulated digestive juices (saliva, stomach and intestine), including inorganic/organic biomacromolecules and digestive enzymes (complete composition, referred to as "Type 1 formulation"), strives for realistic representation of chemical composition of the OGI tract. However, the data robustness requires consideration of analytical feasibility, such as the use of simplified media. Here we present a systematic analysis of the effects exerted by different digestive juice formulations on the dissolution% (or half-life values) of benchmark NMs (e.g., zinc oxide, titanium dioxide, barium sulfate, and silicon dioxide). The digestive juices were progressively simplified by removal of components such as organic molecules, enzymes, and inorganic molecules (Type 2, 3 and 4). The results indicate that the "Type 1 formulation" augments the dissolution via sequestration of ions by measurable factors compared to formulations without enzymes (i.e., Type 3 and 4). Type 1 formulation is thus regarded as a preferable option for predicting NM biodurability for hazard assessment. However, for grouping purposes, the relative similarity among diverse nanoforms (NFs) of a NM is decisive. Two similarity algorithms were applied, and additional case studies comprising NFs and non NFs of the same substance were included. The results support the grouping decision by simplified formulation (Type 3) as a robust method for screening and grouping purposes.