Micro and nanoplastics (MNPs) are environmental contaminants found in food and water. Recent evidence suggests these particles may be linked to intestinal inflammation and changes in gut bacteria, which are key features of Crohn's Disease (CD). This study aims to investigate if patients with Crohn's Disease have a reduced ability to clear these plastic particles and how this affects their immune system and intestinal health.

Micro and nanoplastics may influence Crohn's Disease activity and gut health by impairing microplastic-degrading capacity of the gut microbiome due to the decreased plastic-degrading genes (PDGs) encoding enzymes (e.g., esterases, cutinases, PETases, laccases). Persistent Microplastics (MPs) drive worsening dysbiosis, which in turn amplifies immune activation, evidenced by increase in pro-inflammatory cytokines and disrupts intestinal barrier integrity. The resulting barrier leakage facilitates further MPs translocation, perpetuating disease exacerbation. This study is looking at the effects of micro- and nanoplastics (MNPs) on the gut microbiome, immune function, and intestinal barrier function.

Patients with Crohn's disease (CD) and healthy controls will be recruited during routine clinic visit or on the day of their scheduled colonoscopy following written informed consent.

In this study, demographic data (age, sex, smoking and alcohol status), as well as past medical and surgical history and current medications will be collected. A questionnaire focused on plastic-packaged foods in daily lives will also be administered.

All recruited subjects will have biopsies taken at their scheduled colonoscopy within 4 weeks of recruitment. Stool and blood will be collected cross-sectionally at recruitment.The fecal calprotectin tests and the Harvey-Bradshaw Index (HBI) will be used to assess the severity.

The flow cytometry to quantify cell populations; multiplex ELISA to determine levels of pro- and anti-inflammatory cytokines and a phagocytosis assay will be used for the scientific outcome measurements of the samples collected.

Inclusion Criteria:

Cases:

• Age 18-80 years
• Confirmed diagnosis of Crohn's disease (for cases)
• Ability to provide informed consent.

Control:

• Age 18-80 years old
• No history of major large bowel resection
• Ability to provide informed consent.

Exclusion Criteria:

Cases:

• Antibiotic/probiotic use within 4 weeks
• History of gastrointestinal malignancy
• Presence of stoma
• Currently Pregnant
• Advanced terminal medical illness, e.g. terminal malignancies; end staged renal failure and liver failure

Control:

• Currently Pregnant
• Advanced terminal medical illness, e.g. terminal malignancies; end staged renal failure and liver failure
• Inability in giving consent

Potential subjects will be identified at the Department of Medicine and Therapeutics of the Prince of Wales Hospital, or by personal referral from staff.