Capillary-driven distance-based paper analytical devices for albumin protein and glucose quantification in human whole blood

This study presents a simple and inexpensive distance-based paper analytical device (dPAD) for plasma separation from whole blood samples and its application in monitoring albumin protein and glucose levels using colorimetric and fluorescent distance methods. The developed dPAD consists of a sample zone, a separation zone with hydrophobic wax-patterned lines, a pretreatment zone, and a straight zone channel pre-deposited with chemical reagents for both albumin protein and glucose quantification. Plasma separation relies on the capillarity-driven different flow velocities of blood cells and plasma with varying hydrophilicity in the paper channel. Remarkably, the blood cells are trapped in the separation channel of the device, while plasma can be separated and subsequently flow with a buffer solution to the detection zone by capillary force. Target analyte in plasma content then reacts with its specific reagents, resulting in the change in the color or fluorescent distance signal. Our sensor exhibited remarkable accuracy and precision for the detection of albumin protein and glucose in whole blood samples with an acceptable recovery range between 99.94 and 101.65% and the highest relative standard deviation (RSD) of 4.49%. Furthermore, the results indicated no significant differences between our method and conventional methods for albumin protein and glucose determination in whole blood samples. Additionally, to the best of our knowledge, this method is the first time for the development of the fluorescent dPAD sensor for glucose monitoring. It is also the first demonstration to use a dPAD sensor for the direct detection of both albumin protein and glucose levels in whole blood. Hence, despite its simplicity, the concept offers a more cost-effective and accessible method for plasma separation from whole blood and subsequent albumin protein or and glucose detection. Moreover, it can be extended for further advancements in POC analytical sensing.