Passive mixing microfluidic urinary albumin chip (ual-chip) for chronic kidney disease

Abstract

Described herein is a method for mixing unequal amounts of two reagents to produce a detectable reaction in a microfluidic chip. In one example, there is a fluorescent microfluidic urinary albumin chip (UAL-Chip) that exploits the nonimmunological fluorescent assay. In this chip, we constructed a passive and continuous mixing module, in which the loading process requires only an inexpensive dropper, and the signal is stable over time, as discussed below. We applied a pressure-balancing strategy based on the immiscible oil coverage which highly improves the precision in controlling the mixing ratio of sample and dye. The UAL-Chip has achieved an estimated limit of detection (LOD) of 8.4 μg/ml using albumin standards, which is below the 30 μg albumin per ml urine level considered to be indicative of kidney damage.