Development of a sugar-based polyurethane foam colorimetric sensor for E. coli detection

This study presents the development of a polyurethane-based Escherichia coli sensor, with potential applications in biotechnology and biomedicine, focusing on prevention and non-invasive diagnostic. Sugar-based polyurethane foams were modified through alkaline hydrolysis to introduce primary amine groups, where subsequently the chromogenic agent X-Glu (5-Bromo-4-chloro-3-indolyl b-D-glucuronide sodium salt) was chemically linked to using the EDC/NHS coupling mechanism. Upon interaction with an E. coli-specific enzyme, the sensor displays a visible blue signal. Our findings demonstrate that amine-functionalized foams exhibit improved water sorption, capillarity, and decreased weight loss in aqueous media compared to non-functionalized ones. FTIR-ATR spectra and microbiological tests confirmed the success of functionalization and immobilization procedures. After 21 h, the samples in contact with the liquid medium containing E. coli cell suspensions at a concentration of 108 CFU/mL clearly exhibited a blue signal. For the samples in contact with the lowest concentration tested, 102 CFU/mL, the blue color developed between 49 and 69 h. The final foams can be integrated into different systems supporting a liquid flux, such as urine, and effectively detect E. coli by providing a visual colorimetric signal. This sensor can be adapted to offer a simple and effective solution for E. coli detection, for example, in different clinical settings, eliminating the need for sample processing and contributing to a paradigm shift from reactive approaches to predictive and preventive procedures.