(86a) A Sensor Solution to the Femtomolar Problem in Bladder Cancer

Bladder cancer is recognized as the most expensive malignancy per patient, largely due to the need for persistent, invasive monitoring and biopsies to detect or rule out recurrence—an outcome that occurs in approximately 40% of cases. Urinalysis has emerged as a potential non-invasive screening method; however, its effectiveness is limited by the extreme dilution of biomarkers in the bladder, often reducing their concentrations to the femtomolar range, which poses significant challenges for detection.

In this work, we introduce and mathematically analyze a sensor innovation that addresses this issue by positioning a generic sensor array directly at the source of biomarker efflux within the urinary tract—including the urethra, bladder, ureter, and intrarenal regions. We focus on urothelial malignancies that release biomarkers into the urine and demonstrate that bringing a sensor probe into proximity to the tumor can significantly improve detection sensitivity.

Our data shows that this localized sensing approach can amplify analyte concentration by over 50,000-fold for protein biomarkers with diffusivities on the order of 10⁻¹⁰ m²/s in urine. We also discuss the potential extension of this approach to other cancer types. This work presents a novel solution to the "femtomolar problem" in bladder cancer diagnostics, with the potential to enable earlier detection, reduce invasive procedures, and significantly lower the cost of recurrent cancer monitoring.