A microfluidic microspheres accumulation platform for direct visualization of urine albumin-to-creatinine ratio in patients with chronic kidney disease

The urine albumin-to-creatinine ratio (uACR) level is an essential biomarker for the early screening and monitoring of chronic kidney disease (CKD), particularly among patients with diabetic and hypertension. However, uACR requires quantitative assay, where the use of designated analyzers makes the assays difficult for large-scale screening. In this study, we developed a decentralized, instrument-free microfluidic microspheres accumulation platform (MMAP) that visualizes the uACR in patients with diabetic nephropathy. Albumin inhibits the binding between magnetic microspheres (MMSs) and polymer microspheres (PMSs) due to competitive immunoassay interactions, while creatinine is recognized by the anti-creatinine aptamer, which releases a DNA blocker strand to facilitate connections between MMSs and PMSs through DNA hybridization. The binding of MMSs and PMSs prevents PMSs from escaping magnetic attraction in the inlet, thereby reducing the free PMS accumulation length in the measurement zone of the microfluidic chip. The PMS accumulation length allows for the visual quantification of uACR with excellent selectivity, tolerance to varying pH levels, and high accuracy comparable to that of standard tests in the hospital. As a convenient, low-cost assessment tool that correctly classified all clinical samples in this pilot cohort to evaluate CKD stages from normal to end-stage, this device offers significant benefits for disease self-monitoring and community health services.