A quantitative rapid test for urine creatinine via Fenton's reaction and a self-driven microfluidic device

Urine creatinine plays a pivotal role both as an indicator for kidney impairment and as a normalizer for other urine markers to account for variations in urine volume. Here, we report a quantitative rapid test that converts the urinary creatinine level into a length of a visual bar on a microfluidic device. Hydroxyl radicals in Fenton's reaction is used to cleave an oligonucleotide linker designed to bind magnetic microparticles (MMPs) and polystyrene microparticles (PMPs). Due to creatinine's inhibition to hydroxyl radicals, the creatinine level is reflected by the increase of bound microparticles. Measured by the length of PMP accumulation after magnetic separation on the microfluidic device, we achieved a limit of detection (LOD) of 20.11 mg dL^-1, with high tolerance to interfering factors and a wide pH range. Comparison with the standard method using 21 clinical urine samples yielded a concordance correlation of 0.92, indicating good accuracy and clinical compatibility.