A low-cost paper-based blood urea nitrogen optical biosensor for renal surveillance in fingertip blood

In this study, we developed a low-cost, handheld optical biosensor for measuring blood urea nitrogen (BUN) levels in fingertip blood. This biosensor can connect to a cloud-enabled smartphone for remote monitoring of renal diseases. The biosensor features a simple, stackable and multilayer paper-based strip design, which not only achieves a linear optical fast response to BUN concentration but also reduces the complexity of the optical reader. Excellent detection performance was obtained via a unique photoelectric detection algorithm. The proportional function for calculating the analyte concentration was established using blood samples with different BUN concentrations, resulting in a wide detection range of 2.46-38.14 mM and a low detection limit of 0.03 mM. Clinical sample testing demonstrated the biosensor's high reliability, showing strong agreement with the bulky biochemistry analyzer (gold standard), with a correlation coefficient R2 = 0.9635. It is also capable of connecting to a cloud-enabled smartphone via Bluetooth to transmit test data, which has an easy-to-use interface, thus enabling proactive health management or remote diagnosis. We believe that the proposed BUN biosensor can be a big boost to the daily monitoring of renal diseases and has promising prospects in contributing to the development of the IoMT.