Size-dependent toxicity of microplastics and nanoplastics: insights from the Drosophila melanogaster model

Microplastics and nanoplastics (MNPs) are ubiquitous environmental pollutants that enter organisms and induce multi-system damage. Particle size is a critical determinant of MNPs' bioavailability, biodistribution, and toxic intensity, with smaller particles exhibiting stronger biopermeability and toxic hazards. Drosophila melanogaster (fruit fly) has emerged as an ideal model organism for investigating MNPs' toxic mechanisms due to its short life cycle, clear genetic background, and high genetic homology with humans.This review systematically summarises research on the toxicity of MNPs with different sizes based on the Drosophila model, clarifying the size-dependent toxicity pattern. Large microplastics (1-5 mm) remain in the digestive tract, causing local physical damage and dysbiosis. Small microplastics (1 μm-1 mm) induce intestinal damage, oxidative stress, as well as abnormalities in behaviour and reproduction. Submicroplastics (100 nm-1 μm) can penetrate the intestinal barrier, triggering systemic inflammation and cardiac dysfunction. Nanoplastics (<100 nm) possess the strongest biopermeability, invading cells and organelles to cause DNA damage, immune disorders, and transgenerational toxicity, while also exacerbating synergistic toxicity with heavy metals via 'carrier effects'.This review provides a theoretical basis for MNP risk assessment and highlights the unique value of the Drosophila model in this field.