Detection of albumin using gold nanoparticles-mediated microfluidic paper-based analytical devices

In this work, we develop the rapid diagnostic kit potentially applied as point-of-care testing for kidney disease (nephropathy) through detecting albumin in urine samples. For this purpose, gold-nanoparticle (AuNPs) in combination with anionic dyes of Bromocresol Purple (BCP) and Bromothymol Blue (BTB), which are immobilized onto distance-based microfluidic paper-based analytical devices (d-μPADs), are utilized as sensing reagents. In this device, two mechanisms operate for quantitative and semiquantitative detection of albumin using d-μPAD, which include (1) protein error of pH indicator by direct reaction of albumin with dyes and (2) full corona protein formation of AuNPs with albumin. These synergistic reaction mechanisms facilitate the sharp color change of dyes, easily detected by the naked eye. Some parameters affecting the sensitivity of the proposed method, such as dye concentration, pH, reagent volume ratio, reagent immobilization, and reaction time, are investigated in detail. Inexpensive, disposable, and easy to use without technical expertise for albumin detection are advantages of the proposed method. Additionally, the proposed method has a high precision (RSD: 1.08%) and accuracy (99.38-99.96%).