On-hand tool for CKD monitoring: design of a couple of µPADs for ammonium and urea determination in saliva

Chronic Kidney Disease (CKD), is a condition in which the kidneys malfunction, causing the accumulation of metabolic toxins. Urea is a nitrogenous product of the protein metabolism by the urea cycle, resulting from the toxic NHx convertion. Since its primarily form of secretion is the kidney, urea is one of the most used biomarkers for kidney failure. Microfluidic paper-based analytical devices (μPADs) are a recent concept that has gained a lot of attention in the last few years as on-hand, point-of-care biosensors. These devices have gained a great interest since are capable of performing the analytical determinations in less time and with a more simpler, economic and user- friendly procedure. In this work, a couple of μPADs were developed for the determination of NHx and urea in saliva samples. The determination was based on color change of bromotymol blue indicator (BTB) after the ammonia diffusion through an hydrophobic membrane [1].