Polyisobutylene Micro/Nanoplastics Induce Multi-System Toxicity, Intestinal Barrier Dysfunction, and Neurodegeneration in Drosophila melanogaster

Abstract

Micro/nanoplastics (MNPs) are increasingly recognized as a persistent environmental contaminant of concern, yet polyisobutylene (PIB), an industrially significant polymer used as industrial sealants, adhesives, cable insulation, lubricant additives, and chewing gum bases, remains poorly studied relative to more commonly studied plastics such as polyethylene terephthalate (PET), polystyrene (PS), and polyethylene (PE). This study investigated the multisystem toxicological effects of chronic dietary exposure to PIB-MNPs in Drosophila melanogaster. PIB-MNPs (> 5 micron) were synthesized via the solvent evaporation method and characterized using scanning electron microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR), confirming successful synthesis. Flies were chronically exposed to PIB-MNPs (1, 2, or 3 mg) alongside an SDS control and a water control to 50 mg of yeast over 21 days, with toxicological outcomes assessed via survival analysis, climbing assays, fluorescence brain imaging, fertility/fecundity assays, the Smurf gut-permeability assay, Ellman's AChE activity assay, and RT-qPCR analysis of Stat92E expression, a marker of inflammation. Chronic exposure to PIB-MNPs reduced survival, with females exhibiting markedly greater susceptibility than males. Exposure progressively impaired locomotor performance and induced brain vacuolization suggestive of neurodegeneration, peaking at day 15. AChE activity declined in a concentration-dependent manner by day 21. Female fecundity, egg-hatching rate, and ovarian egg-chamber maturation were significantly reduced, while male gonadal cyst cell numbers remained largely unaffected. PIB-MNPs exposure also induced a positive Smurf phenotype, indicating compromised intestinal barrier integrity and upregulated Stat92E expression, consistent with activation of a systemic stress response. Notably, several endpoints showed non-monotonic, concentration-independent trends, suggesting particle aggregation may influence effective bioavailability. Collectively, these findings establish PIB-MNPs as a multi-system toxicant in Drosophila.