Point-of-Care Smartphone/Resistive-Nanosensor Platform for Measurement of Urea and Creatinine in Minimal Volume of Whole Blood

Chronic kidney disease (CKD) is an epidemiological disease that afflicts a significant portion of the U.S. population and is expected to grow significantly over the next decade. Traditionally, CKD is diagnosed through quantification of serum creatinine or blood urea nitrogen, which is indicative of renal dysfunction when levels are elevated. In this work, an integrated point-of-care smartphone/resistive nanosensor is developed for rapid and sensitive detection of creatinine and urea using a minimal volume of whole blood for screening of CKD. The nanosensor utilizes the proton-sensitive transport properties of polyaniline nanofibers (PAnNFs) coated on a gold interdigitated electrode and the catalytic activity of creatinine deiminase/urease. Creatinine deiminase/urease facilitates the hydrolysis of creatinine/urea to ammonia, which results in dedoping of PAnNFs, thereby decreasing the conductance of the film. As such, the change in conductance of PAnNFs is proportional to creatinine/urea concentrations within a sample, allowing for assessment of renal function. Further, a mobile app was developed for this nanosensing platform to process, display, track, and share results. Under optimal conditions, the nanosensor demonstrates a wide dynamic range of 0.01 to 0.1 mM for urea and 0.05 to 1.0 mM for creatinine, and detection limits of 0.0059 mM for urea and 0.018 mM for creatinine with <10% relative standard variation, in water. Preliminary real-sample testing was performed by spiking creatinine and urea in whole blood, providing a strong linear relationship with response intensity. As such, this integrated nanosensing platform demonstrates feasibility for screening of renal function in real-world application.