Plastic pollution has become one of the most serious environmental challenges today, with macro- and microplastics continuously degrading into much smaller particles known as nanoplastics (NP) through physical, chemical, and biological processes. These nanoscale particles have spread across various ecosystems and entered the food chain, raising global concerns about their potential impacts on human health and the environment. NPs may exist as homogeneous or mixed aggregates, possessing unique physicochemical characteristics that enhance their interaction with biological systems.
According to the International Organization for Standardization (ISO), nanoparticles—including NPs—are materials with sizes ranging from 1 to 100 nanometers. Meanwhile, the International System of Units (SI) extends this definition to include plastic particles up to 1000 nanometers (1 micrometer). Due to their extremely small size and large surface area, NPs have a high capacity to bind pollutants and cross biological membranes. Once inside an organism, they can accumulate within cells and potentially trigger toxic effects.
The ability of NPs to penetrate and infiltrate cellular structures has raised serious health concerns. Studies have revealed that NPs can enter cells via endocytosis or passive diffusion, reach intracellular compartments, and interact with essential biomolecules. Their presence has been linked to oxidative stress, inflammation, and cellular dysfunction, which may result in liver damage, respiratory issues, skin disorders, and reproductive health problems. However, research on the long-term health effects of nanoplastic exposure remains limited.
To better understand these risks, in vitro toxicological models such as 3T3 fibroblast cell cultures are widely used due to their sensitivity, reproducibility, and relevance in assessing cell stress, morphological changes, and nanoparticle uptake. In vivo models, such as the laboratory rat Rattus norvegicus, are also utilized due to their physiological similarities to humans. One commonly studied type of NPs is polystyrene nanoplastics (PSNPs), which originate from widely used polystyrene plastics that are resistant to degradation and prone to fragmentation into persistent micro- and nanoparticles in the environment.
PSNPs smaller than 100 nm can directly interact with lipid membranes and cellular proteins, thereby influencing biological processes at the molecular level. Once inside the body, PSNPs are difficult to eliminate and may accumulate in the digestive tract. Some particles can even penetrate the intestinal wall, enter the bloodstream, and spread to various tissues and organs. Unfortunately, the intracellular behaviour and long-term biological impacts of these particles are still not well understood, highlighting the need for further investigation.
Nanotoxicology studies aim to explore how PSNPs interact with cellular systems and their potential to disrupt physiological functions. So far, PSNPs have been found to enter cells through several main pathways, including endocytosis, protein corona formation, and direct lipid membrane interactions. However, many aspects of these mechanisms remain unclear, especially regarding their long-term health effects.
Recent evidence shows that PSNPs can efficiently enter cells, accumulate in the cytoplasm, and even reach the cell nucleus in both 3T3 fibroblasts and rat hepatocytes. Their presence triggers noticeable morphological changes, cytoplasmic disorganization, and signs of cellular stress. These observations suggest that PSNPs interfere with critical cellular functions, both metabolic and structural. The process likely involves active endocytosis and potential nuclear transport. The accumulation of PSNPs in vital subcellular compartments poses risks to membrane integrity, induces oxidative stress, and disrupts nuclear functions—raising serious concerns about genotoxicity and long-term cellular health.
Therefore, it is crucial for the scientific community and the public to continue investigating the risks of NP exposure, particularly over the long term. Future research should focus on understanding molecular toxicity mechanisms, including inflammation, oxidative damage, and genetic instability, which may serve as the basis for a range of serious health issues.
Author: Prof. Dr. Alfiah Hayati, Dra., M.Kes
