Abstract Background Inflammatory Bowel Disease (IBD), including Crohn’s Disease (CD), is a chronic inflammatory disorder of the gut. The pathogenesis of inflammatory bowel disease (IBD) involves complex interactions between genetics, environment, and the gut immune system. Microplastics (MPs), as pervasive environmental contaminants, are ingested and have been detected in human tissues1. Emerging evidence suggests a potential link between MP exposure and IBD2, but direct evidence of MPs within the intestinal mucosa and its association with disease activity is lacking. This study aimed to quantify and characterize MPs in the intestinal mucosa of patients with Crohn’s disease (CD) and to evaluate their correlation with endoscopic disease severity. Methods Between March 2025 and September 2025, a total of 90 participants were enrolled, including 20 with active CD, 20 with CD in remission,and 10 healthy controls (with ≤0.2 cm polyps). Mucosal biopsy samples were obtained during colonoscopy. High-resolution digital imaging was performed for morphological analysis. Chemical identification of MPs was conducted using micro-Fourier transform infrared spectroscopy (μ-FTIR) and Raman imaging. Polymer identification required spectral matching (80% similarity, with characteristic peak alignment) and expert validation in complex matrices. Results MPs were ubiquitously detected in the intestinal mucosa across all groups. The median mucosal MP concentration was significantly higher in patients with active CD (162.7 Pcs/g) compared to those in remission (87.31 Pcs/g, p 0.0001) and healthy controls (61.28 Pcs/g, p 0.0001)(Figure 1). A total of 7 polymer types were identified, with polyethylene terephthalate (PET,25-51%), polypropylene (PP, 12-27%), and polyethylene (PE, 20%-22%) being the most predominant. The majority of MPs were fragments and particles, transparent (38%-47%)or white (30%-40%) in color, and 10-50 μm in diameter(55%-81%). Crucially, a significant positive correlation was observed between mucosal MP concentration and the SES-CD endoscopic score in the active CD group (r = 0.628, p 0.01)(Figure 2). Conclusion This study provides novel evidence that mucosal MPs deposition is significantly elevated in active CD and correlates with endoscopic severity. These findings suggest that microplastic exposure may contribute to disease pathogenesis or that IBD enhances MPs retention in the gut. Further investigation is warranted to elucidate the underlying mechanisms. Our results also highlight mucosal MPs quantification as a promising tool for assessing human MPs exposure and its potential health impacts in IBD. References: 1. Donisi I, Colloca A, Anastasio C, et al. Micro(nano)plastics: an Emerging Burden for Human Health. Int J Biol Sci. 2024;20(14):5779-5792. 2. Yan Z, Liu Y, Zhang T, et al. Analysis of Microplastics in Human Feces Reveals a Correlation between Fecal Microplastics and Inflammatory Bowel Disease Status. Environ Sci Technol. 2022;56(1):414-421. Conflict of interest: Ms. Cui, Yitong: No conflict of interest Lin, Jue: No conflict of interest Zhang, Huoyan: No conflict of interest Liu, Tao: No conflict of interest Deng, Jun: No conflict of interest Zhang, Min: No conflict of interest Wang, Wei: No conflict of interest Zhi, Min:
Cui et al. (Thu,) studied this question.