Abstract
Polystyrene (PS) is a synthetic polymer extensively used across various industries, but its widespread use and improper disposal have led to environmental concerns due to the formation of microplastic particles (<5 mm). These PS microplastics (PS MPs), generated through degradation, mechanical disintegration, manufacturing by-products, and inadequate recycling, can absorb environmental toxins or leach harmful additives, posing potential risks to living organisms. In this study, we investigated the in vivo toxicological effects of synthesised PS micro/nanoplastics (PS MNPs) within a broad particle size range (100-1000 nm) using the Drosophila melanogaster model. Adult male flies and third-instar larvae were used to assess physiological and behavioural effects. The study examined PS MP toxicity at two exposure levels (30 and 300 µg/mL), providing insight into dose- and size-dependent biological effects. Exposure to PS MNPs caused significant behavioural and biochemical impairments in both larval and adult stages. Biochemical analyses revealed an elevation in the biomarkers for cellular stress, indicating redox imbalance. These effects were further supported by the transcriptional upregulation of key stress response genes, including Hsp70Bc, rpr, cat, p53, and sod, demonstrating that PS MNPs elicit oxidative stress and cellular toxicity in Drosophila. Our findings provide insight into PS MP toxicity by integrating particle size and concentration with behavioural and oxidative stress-related endpoints in a genetically tractable in vivo model.
