Stability of colorimetric results in the detection of urine biomarkers using a paper-based analytical device.

Urinalysis allows obtaining information about many of the body's functions. Normally, urine is a very easily collected specimen, but in some cases, it can be an uncomfortable process. Moreover, standard methods such as microscopic examination or urine culturing represent time-consuming procedures. In this regard, this work explores the design of a device that combines disposable diapers, as a platform for sample collection, with part of the dipsticks method. Even though this is a desirable combination for a faster and comfortable approach, it is also convenient to extend the prescribed time, provided by the dipstick manufacturer, to read the results. This allows the stability and validity of the results for longer, preferably until the moment of the diaper changing, and it was also considered in the design. The desired conditions were reproduced for the reagent pads of glucose and nitrite. The results show that the RGB profile, obtained in glucose detection, varied after approximately 60 min. However, when the developed colors are visually compared with the reference colors, the results suggest that there were not significant variations. In the nitrite assay, by analyzing the RGB profile or by visual comparison with the reference colors, the color does not appear to change over time, but the results were not the expected. It seems that the proposed design is promising regarding results stability, but more experiments need to be done to check if the variations are constant for more biomarkers in the conditions provided by the device.