Semiquantitative assessment of the distribution of microplastic particles in the body during acute exposure

Introduction. Microplastics pose a significant health threat due to their toxicity and capacity for bioaccumulation. Although studies have confirmed their detrimental effects on biological systems, the mechanisms governing particle accumulation and particle distributions have not been sufficiently studied. The aim of our study was to develop and experimentally validate a semi-quantitative method to assess these processes on the base of investigation of the distribution of plastic microparticles in the organism under acute in vivo experimental conditions using a semi-quantitative method.Materials and methods. Twelve female Wistar rats were divided into four groups. Animals received intracardiac injections of polystyrene microparticle suspensions (100, 500, and 1000 nm in diameter) or physiological saline solution. The accumulation of microparticles in six organs was evaluated using a semi-quantitative scoring method based on fluorescence microscopy and a rank-scale assessment. Data were analyzed using bootstrap methods with Holm–Bonferroni corrections, and differences were considered significant at p < 0.05.Results. Following intracardiac administration, polystyrene microparticles measuring 100, 500, and 1000 nm were detected in the liver, kidneys, and lungs. They localized primarily in hepatic triads, the renal cortex, and the acinar regions and alveolar ducts of the lungs. The highest levels were observed upon administration of 1000-nm particles. Semi-quantitative analysis revealed liver and lung tissues to accumulate significantly more microparticles of the 1000-nm in size, while the kidneys showed greater accumulation of the 100-nm particles.Limitations. This study was limited to examining the distribution of three microparticle size groups in a single animal model (laboratory rats, only 3 animals in each group) under acute toxicological conditions.Conclusion. The intensity and abundance of fluorescent tissue elements depend on particle size and may be associated with the formation of microparticle conglomerates. While the semi-quantitative method allowed identifying certain distribution patterns, further research involving quantitative approaches is required to enhance the accuracy and specificity of these findings.Compliance with ethical standards. All experiments in this study were conducted in accordance with European Convention standards for the protection of vertebrate animals used for research and other scientific purposes. The study protocol was approved by the local ethics committee (Approval No. 01-10 from October 9, 2024).Contribution: Ahmadeev A.R. – conducting the experiment, data collection and processing, writing the text, preparing figures; Ryabova Yu.V. – research concept and design, writing the text; Karimov D.O. – research concept and design, scientific editing of the text; Khusnutdinova N.Yu. – conducting the experiment; Kudoyarov E.R. – data collection and processing, writing the text; Valova Ya.V. – research concept and design, data collection and processing. All authors are responsible for the integrity of all parts of the manuscript and approval of the manuscript final versionConflict of interest. The authors declare no conflict of interest.Funding. The study was carried out within the framework of the sectoral research program of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing for 2021–2025.Received: December 23, 2024 / Revised: January 15, 2025 / Accepted: March 26, 2025 / Published: June 27, 2025