Rapid Point-of-Care Quantification of Urinary Tract Infection Biomarker Xanthine Oxidase

Abstract Antimicrobial resistance is a growing global health threat. Overuse of antimicrobial drugs is a main driver of resistance, with urinary tract infections (UTIs) a common indication for antibiotic use. To improve UTI treatment and reduce antimicrobial resistance, real-time diagnostic tools for monitoring the host immune response are needed. Xanthine oxidase (XO) is an enzyme that is elevated in UTIs and shows potential for sensitive and selective detection of infection. We developed a rapid and sensitive point-of-care electrochemical sensor for XO detection by using a simple manufacturing approach. The sensor consists of a disposable carbon electrode embedded in a capillary fill chamber designed for point-of-care sample collection. After urine collection, XO catalyzes its substrate while changing the oxidation state of a secondary electron acceptor. The magnitude and rate of this redox shift reflects XO activity, enabling quantification of XO in urine. We demonstrate minimal intersensor variability of less than 5%, resulting in a calibration with an R2 of 0.985 across eight individual sensors. The capillary fill device was optimized to enable efficient substrate dissolution, reducing the time to result from 10 min to just 2 min. This approach enables calibration-free detection of XO in artificial and spiked human urine samples within 2 min of sample collection in both artificial urine and spiked human urine samples.