Smart colorimetric label based on chitosan-grafted cresol red for early detection of catheter blockage and infection through urinary pH monitoring.

This study presents a smart, non-invasive colorimetric sensor designed for the early detection of catheter-associated urinary tract infections (CAUTIs) and impending catheter blockage. The sensor was developed by covalently grafting cresol red onto chitosan (CS-g-CR) via a Mannich reaction, producing a biocompatible, pH-responsive material exhibiting strong dye retention and stable, visible color transitions across the urinary pH range. The material was formulated into a water-based screen-printable ink and applied to cotton fabric, yielding flexible labels capable of detecting alkaline shifts associated with Proteus mirabilis infection. In an in vitro bladder model, the printed labels provided up to 20 h of advance warning prior to complete catheter blockage. Color changes were quantified using smartphone-based RGB analysis, enabling objective and real-time monitoring. This low-cost sensing platform holds promise for point-of-care applications aimed at improving early diagnosis and reducing complications in long-term catheterized patients.