Eco-corona: A new frontier in understanding micro- and nanoplastic-gut interactions

Abstract

Plastics released into natural environments undergo complex transformations, ending in the spontaneous formation of an “eco-corona”, a dynamic layer of adsorbed organic molecules, biomolecules, and microorganisms. This eco-corona profoundly alters the physicochemical identity of micro- and nanoplastics, modulating their environmental fate, pollutant adsorption, cellular uptake, and toxicity. Emerging evidence shows that eco-corona-coated plastics can act as vectors for environmental pollutants and microbial pathogens, raising significant concerns for ecosystems and human health, particularly in the gastrointestinal tract. Eco-corona dynamics influence colloidal stability, pollutant vectorization, immune responses, and interactions with the gut microbiota, potentially contributing to barrier dysfunction, inflammation, and microbiota dysbiosis. However, major knowledge gaps persist regarding the real-world composition and evolution of eco-coronas, their interplay with biological coronas, and their long-term impacts on health. This mini review synthesizes current insights into eco-corona formation, its modulation of micro- and nanoplastic behavior and toxicity, and highlights critical research priorities to better understand and mitigate the emerging risks at the interface between plastic pollution and gastroenterology.

Key Words: Eco-corona; Microplastics; Nanoplastics; Environmental toxicity; Gut microbiota; Pollutant vectorization; Gastrointestinal health; Gastrointestinal barrier

Core Tip: Eco-coronas form spontaneously on micro- and nanoplastics in natural environments, giving them new bioactive surfaces that influence their interactions with living systems. By modifying the behavior of plastics in the gut, influencing microbial composition, immune responses, and barrier integrity, eco-coronas appear as a critical yet insufficiently explored factor in evaluating the health risks associated with plastic ingestion. Understanding these transformations is key to advancing both environmental and gastrointestinal toxicology.

INTRODUCTION

Plastics released into the environment undergo a series of physical, chemical, and biological transformations that progressively reduce their size and alter their surface properties, ultimately leading to the formation of micro- and nanoplastics (MNPs). The initial stages typically involve photodegradation induced by ultraviolet radiation, which breaks down polymer chains and introduces oxygen-containing functional groups[1]. This oxidation weakens the plastic matrix, making it more susceptible to mechanical fragmentation from wind, wave action, or abrasion against sediments and rocks[2]. Over time, thermal oxidation, hydrolysis, and biofouling by microbial communities further degrade the material and facilitate its disintegration[3]. These processes result in MNPs with increased surface roughness, altered chemical reactivity, and enhanced potential for eco-corona formation. The rate and extent of degradation depend on the polymer type, environmental conditions, and exposure duration, with plastics like polyethylene (PE) and polypropylene showing particularly high fragmentation potential in both marine and terrestrial environments[4]. While the concept of protein coronas on engineered nanomaterials is well established[5], the eco-corona on environmental plastics has only recently gathered attention, particularly regarding health and ecological implications. Eco-corona-coated plastics no longer behave as pristine materials; instead, they acquire new biological identities that modulate cellular uptake, immune responses, pollutant adsorption, and toxicity[6].

Recent studies show that eco-coronas can act as vectors for environmental pollutants, heavy metals, and microbial pathogens, thereby amplifying potential health risks through mechanisms such as synergistic toxicity, immune system modulation, and Trojan horse effects, in which harmful substances or microorganisms are covertly transported into biological systems by being hidden within or adsorbed onto MNPs, allowing them to bypass biological defenses and enter cells more easily[7]. Their composition is highly dynamic, shaped by environmental conditions (such as organic matter type, pH, and ionic strength) and intrinsic particle properties (such as polymer type and surface aging)[8]. Despite growing concern, substantial knowledge gaps persist regarding how eco-corona formation influences the interactions between MNPs and host organisms, particularly the gut microbiota and immune barriers[9]. This mini review aims to summarize the current understanding of eco-corona formation, its drivers, its modulation of MNPs properties, its role in transporting chemical and biological hazards, and its emerging impact on health, while highlighting critical research perspectives.

ECO-CORONA FORMATION: MECHANISMS AND COMPOSITION

Upon release into natural environments, MNPs interact immediately with surrounding biomolecules, leading to spontaneous eco-corona formation[10]. This process is governed by a combination of van der Waals forces, hydrophobic interactions, hydrogen bonding, and electrostatic attractions[6]. Adsorbed molecules include humic substances, extracellular polymeric substances (EPS), proteins, lipids, polysaccharides, and small metabolites[11]. The eco-corona composition is highly sensitive to both the type of polymer, which determines surface energy and hydrophobicity, and environmental parameters such as ionic strength, temperature, and pH[12]. Aging processes, including photochemical degradation and oxidative weathering, generate surface functional groups (e.g., carbonyl, hydroxyl) that enhance the complexity and reactivity of the eco-corona[13].

Recent studies have shown that eco-corona composition varies significantly across environments, shaping how plastics interact with surrounding biotic and abiotic components. In freshwater systems, eco-coronas are typically enriched with humic substances, whereas in marine environments they are dominated by microbial EPS[14,15]. In soils, the eco-corona is generally composed of humic and fulvic acids, proteins, lipids, polysaccharides, microbial cells, and inorganic particles such as clay minerals[16]. Compared to aquatic systems, the soil eco-corona reflects a more complex and heterogeneous mixture. These compositional differences influence the surface properties of plastic particles and modulate their interactions with pollutants such as heavy metals, polycyclic aromatic hydrocarbons, and pesticides[17], as well as with soil microbiota and biotic interfaces like plant roots or soil fauna.

Significantly, the eco-corona evolves dynamically through competitive adsorption phenomena, commonly referred to as the “Vroman effect”, where higher-affinity biomolecules gradually displace weaker ones[18,19]. This continual remodeling further complicates predictions of MNP behavior and biological interactions in real environments[20,21]. Advanced spectroscopic and omics approaches are necessary to resolve the molecular diversity and functional properties of eco-coronas[22]. Table 1 presents the main components identified in the eco-corona, including those commonly found in soil, freshwater, and seawater environments. Figure 1 illustrates the sequence of eco-corona formation, pollutant adsorption, microbial colonization, and the subsequent impacts on gut physiology and microbiota.

Figure 1 Schematic representation of the origin and potential toxic effects of eco-corona-coated micro- and nanoplastics. The process begins with the fragmentation of plastic debris into microplastics (MPs) and nanoplastics under the influence of environmental stressors such as ultraviolet radiation, mechanical abrasion (e.g., waves), microbial activity, and temperature fluctuations (step 1). Once fragmented, these pristine nano- and microplastics interact with environmental macromolecules, including lipids, proteins, humic substances, and pollutants, leading to the formation of an eco-corona on their surface (step 2). These eco-corona-coated nano- and microplastics can then interact with living organisms, including plants, animals, and humans, at cellular or systemic levels, potentially disrupting biological functions (step 3). Ultimately, these interactions may lead to ecotoxic effects in ecosystems and adverse health outcomes in humans, such as microbiota dysbiosis (step 4). NMs: Nano-microplastics. Some vector elements used in this figure were provided by Vecteezy (available from: https://www.vecteezy.com/).

Table 1 Adsorbed compounds on micro- and nanoplastics biomolecules.

Compound	Environmental occurrence	Environmental relevance
Proteins	All environments	Facilitate cellular uptake mechanisms
Lipids	All environments	Enhance hydrophobic interactions
Polysaccharides	Aquatic systems	Promote biofilm development
Nucleic acids	All environments	Support intercellular communication and adhesion
Humic acids	Soil, freshwater	Major organic fraction of soil and freshwater; influences sorption processes
Fulvic acids	Soil	Modulate redox reactions and metal mobility
Amino acids	Soil	Adsorb onto plastic surfaces in terrestrial systems
Nucleotides	Soil	Fundamental building blocks of genetic and metabolic materials
Phenylpropanoids	Soil	Derived from plant degradation; may affect microbial and enzymatic interactions
Pollutants
Heavy metals	All environments	Represent vectors for metal toxicity via surface binding
PAHs	All environments	Enhance pollutant sorption and increase toxicological risks
PCBs	All environments	Persistent organic pollutants; accumulate and biomagnify in ecosystems
Pesticides	All environments	Agricultural contaminants transported via plastic vectors
Microbiological components
Microbial EPS	Marine systems	Contribute to biofilm formation and microbial colonization on plastics

PAHs: Polycyclic aromatic hydrocarbons; PCBs: Polychlorinated biphenyls; EPS: Extracellular polymeric substances.

ECO-CORONA MODULATION OF MNP PROPERTIES

Eco-corona formation alters the surface properties of plastics, modifying their physicochemical behavior and environmental interactions, significantly altering their fate and biological interactions. Surface charge modulation due to adsorbed biomolecules affects colloidal stability, aggregation, and interactions with cells and other particles. Changes in hydrophobicity impact the dispersibility of plastics in aquatic media and the tendency to sorb hydrophobic pollutants[23]. Colloidal stability can be improved through steric hindrance and electrostatic repulsion, but it can also be disrupted when particles are linked together by bridging flocculation. Consequently, eco-corona-modified plastics can persist longer in suspension or settle rapidly, influencing their environmental distribution[24].

Biologically, eco-corona-coated particles exhibit altered rates and pathways of cellular uptake. Recognition by scavenger receptors, modulation of endocytosis, and differential intracellular trafficking have been reported[15,17,18]. Experimental studies show that particles exposed to natural aquatic environments, acquiring an eco-corona, are more efficiently internalized by macrophages via scavenger receptor-mediated phagocytosis, whereas pristine particles exhibit minimal uptake under similar conditions[14]. Spectroscopic analyses confirm that the eco-corona comprises adsorbed biomolecules such as proteins, lipids, nucleic acids, and carbohydrates, which enhance particle-cell interactions and facilitate endocytosis. Once internalized, these coated particles follow altered intracellular trafficking pathways and may accumulate in lysosomes[25], triggering oxidative stress and immune responses. Moreover, the eco-corona serves as a hotspot for pollutant accumulation, leading to enhanced vectorization of contaminants. This raises concerns regarding combined or synergistic toxicities, where MNPs act as carriers for chemicals and microorganisms that otherwise would have lower bioavailability[26].

ECO-CORONA AS A VECTOR FOR BIOLOGICAL AND CHEMICAL HAZARDS

The eco-corona enables MNPs to act as efficient vectors for a broad spectrum of hazards. Ramsperger et al[14] demonstrated that MNPs exposed to aquatic environments show significantly higher internalization by macrophages, attributed to eco-corona formation. Conversely, Ekvall et al[15] reported that eco-coronas reduced nanoparticle toxicity in Daphnia magna, highlighting a complex balance between protection and facilitation of hazards. Giri et al[17] and Natarajan et al[19] showed that EPS-derived eco-coronas can mitigate the combined toxicity of pollutants such as bisphenol A and nanoplastics. Other studies demonstrated enhanced adsorption of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and heavy metals onto eco-corona-coated plastics, facilitating bioaccumulation and secondary toxicity[27].

The composition of the eco-corona forming on MNPs is highly heterogeneous and depends on both the physicochemical properties of the plastic and the surrounding environmental matrix. Studies have shown that plastics exposed to soil environments acquire eco-coronas rich in lipids, nucleosides, phenylpropanoids, and amino acids, likely through direct adsorption or via macromolecule-mediated interactions[16]. In aquatic systems, the eco-corona often includes proteins, polysaccharides, and microbial EPS, which facilitate microbial colonization and biofilm formation[28]. Additionally, eco-coronas can enhance the adsorption of co-contaminants, thereby increasing the environmental mobility and toxicity of plastic particles[29].

Beyond chemical vectors, eco-coronas promote microbial colonization and survival on plastics. This “plastisphere” is enriched with potentially pathogenic and antibiotic-resistant bacteria[30], raising concerns about environmental and food chain transmission. Although the eco-corona is influenced by environmental context, detectable patterns emerge based on polymer properties. For instance, PE rapidly adsorbs metabolites from soil, forming a stable ecocorona via direct metabolite adsorption or macromolecule-mediated bridging[16]. Meanwhile, polymers such as PE terephthalate and polystyrene, especially after aging and exposure to ultraviolet, exhibit higher affinity for proteins, resulting in eco-coronas that support distinct biofilm communities. Surface aging increases roughness and oxygen-containing functional groups, enhancing corona complexity across polymer types and promoting pollutant binding and microbial adhesion[31,32].

IMPACTS ON HUMAN AND ANIMAL HEALTH

Eco-corona-modified plastics interact intimately with biological barriers. Upon ingestion or inhalation, eco-corona properties influence mucosal adhesion, epithelial penetration, and immune activation[33]. Altered cellular uptake and extended tissue retention of plastics, driven by eco-corona shielding mechanisms, may intensify the risks associated with chronic exposure. Elevated reactive oxygen species generation, mitochondrial damage, lipid peroxidation, and DNA fragmentation have been documented following eco-corona-modified MNP exposure. These stress responses contribute to inflammatory processes implicated in diseases such as asthma, cardiovascular disease, and neurodegenerative disorders[34]. The gut microbiota appears particularly vulnerable to disruption by MNPs, a susceptibility that may be further exacerbated when microplastics (MPs) acquire an eco-corona. Experimental studies in mice and zebrafish have demonstrated that ingested eco-corona-modified MPs can significantly alter the composition and diversity of the gut microbiota, leading to dysbiosis marked by a decline in beneficial commensal bacteria and a rise in opportunistic taxa[7].

These shifts are often accompanied by a reduction in short-chain fatty acid production, key microbial metabolites involved in maintaining epithelial integrity and regulating immune responses[35]. Furthermore, MPs have been shown to impair gut barrier function by disrupting tight junction proteins, increasing intestinal permeability, and promoting low-grade inflammation. While the role of the eco-corona in modulating these effects has yet to be fully elucidated, its influence on surface chemistry and co-contaminant loading may enhance the capacity of MPs to interfere with host-microbe interactions and barrier integrity[36].

These coated particles affect gastrointestinal health through multiple, interrelated mechanisms. By altering surface charge, hydrophobicity, and aggregation behavior, the eco-corona modifies the physicochemical properties of MPs. This may influence the bioavailability and interactions with the intestinal epithelial surfaces of these modified MNPs. Moreover, the eco-corona can act as a carrier for co-contaminants, such as heavy metals, persistent organic pollutants, and pathogenic microorganisms, thereby increasing the likelihood of intestinal inflammation and immune activation upon ingestion. Once in the gut, these particles may exacerbate dysbiosis and metabolic disturbances[37]. They have also been shown to impair intestinal barrier function by disrupting tight junction proteins and promoting oxidative stress, ultimately contributing to increased gut permeability and chronic low-grade inflammation[27]. In aquatic organisms, eco-corona-coated plastics have been linked to bioaccumulation of pollutants, reproductive impairments, oxidative damage, and behavioral alterations[38]. While direct evidence in humans remains limited, parallels with findings from mammalian models justify serious concern.

To date, no epidemiological studies have directly examined the health impacts of ecocorona-coated MNPs in humans, largely because it remains extremely difficult to trace the environmental history and surface properties of internalized particles. However, a landmark observational study published in the New England Journal of Medicine (2024) detected MNPs, primarily PE and polyvinyl chloride, in about 58% of carotid artery plaques taken from patients during surgical removal[39]. Over a mean follow-up of approximately 34 months, individuals with detectable MNPs in plaque exhibited a 4.5-fold higher risk of myocardial infarction, stroke, or death compared to those without detectable plastics (adjusted hazard ratio = 4.53, 95% confidence interval: 2.00-10.27).

Conducting epidemiological studies that explicitly link eco-corona characteristics to health outcomes would require advanced analytical techniques to characterize particle coronas in situ and rigorous control of confounders, complicating both study design and interpretation. The detection of MNPs in human feces confirms that ingestion and gastrointestinal transit occur[40]. However, whether these excreted particles retain their original environmental eco-coronas or instead acquire new biomolecular coatings during digestion remains unknown. As highlighted by Hartmann et al[41], the eco-corona critically alters MNP identity and biological interactions, yet its fate within the human gastrointestinal tract has not been investigated. This represents a major gap in our understanding of how MNPs interact with the gut environment and influence health outcomes through mechanisms such as barrier disruption, immune modulation, or microbiota alteration.

RESEARCH GAPS AND PERSPECTIVES

Despite recent advances, significant knowledge gaps persist in understanding the eco-corona and its implications for MNP toxicity. Comprehensive characterization of eco-corona composition under environmentally realistic conditions remains limited. Employing multi-omics approaches alongside advanced mass spectrometry and high-resolution microscopy is essential to map the molecular diversity and functional roles of eco-coronas. The dynamic evolution of eco-coronas across environmental gradients, such as freshwater, marine, soil, and atmospheric systems, and over time, remains poorly understood[32]. Clarifying how these variations affect plastic bioavailability, pollutant adsorption, and toxicity is critical for accurate hazard prediction.

Another emerging frontier involves the interplay between eco-corona formation and protein coronas that develop upon biological contact. The structure and function of hybrid coronas, and their influence on immune responses, intracellular trafficking, and microbial interactions, remain to be fully elucidated[42]. In addition, the mechanistic links between eco-corona-mediated disruption of the gut microbiota and downstream systemic health effects, including inflammation and epithelial barrier dysfunction, are still speculative and warrant focused investigation[43]. Current toxicological models often underestimate the complexity introduced by eco-corona-modified plastics. There is a pressing need for more sophisticated in vitro and in vivo models that reflect environmentally relevant corona compositions and behaviors.

Finally, studies addressing chronic, low-dose, and multigenerational exposures to eco-corona-coated plastics are scarce. Establishing dose-response relationships and identifying biomarkers of eco-corona exposure will be essential for future environmental and health risk assessments. To date, no epidemiological studies have directly examined the health impacts of eco-corona-coated MNPs in humans, largely because it remains extremely difficult to trace the environmental history and surface properties of internalized particles.

CONCLUSION

The eco-corona fundamentally redefines the environmental and biological behavior of MNPs. Far from being inert particles, eco-corona-coated plastics act as dynamic biological entities capable of transporting hazardous pollutants and microorganisms and triggering complex host responses. Future research must prioritize realistic environmental scenarios, mechanistic studies, and integrative modeling approaches. Regulatory frameworks must evolve to consider eco-corona dynamics when evaluating MNP risks. Recognizing the eco-corona as a critical mediator between MNPs and biological systems is essential to accurately assess, mitigate, and eventually control the health and environmental impacts of plastic pollution in the Anthropocene.

Managing the risks associated with eco-corona-coated MNPs presents a multifaceted challenge, as these dynamic surface layers can enhance pollutant adsorption, microbial colonization, and toxicity. Currently, no specific intervention strategies exist to selectively prevent or mitigate eco-corona formation in the environment. However, risk reduction can be approached through upstream actions such as reducing plastic emissions into natural environments, improving wastewater treatment technologies to retain or degrade MNPs, and limiting the release of co-contaminants that are known to adsorb onto plastic surfaces. In parallel, research efforts are needed to develop surface-engineered plastics with reduced corona-forming capacity or to identify microbial or enzymatic systems capable of degrading eco-corona-coated particles. Ultimately, understanding the eco-corona as a modifiable interface opens new avenues for controlling MNP behavior and toxicity. Incorporating eco-corona dynamics into environmental risk assessments and regulatory frameworks will be essential for anticipating long-term impacts and designing effective mitigation strategies.