A Metal–Organic Gel Actualized Microfluidic-Paper Analysis Device for Detecting Multiple Blood Biomarkers of Metabolic Diseases in Point-of-Care Testing

Colorimetric-based assays are convenient for detecting biomarkers in point-of-care testing (POCT). However, their application is hampered by natural color of whole blood or complex pretreatment procedures such as separation of plasma and/or dilution of plasma and short storage time for peroxidase. To overcome these problems, we developed a metal–organic gel (MOG)-based double-functional microfluidic-paper analysis device (MOG-μPAD) for directly quantifying glucose, uric acid, xanthine, and creatinine from whole blood. We used Cu/Co-MOG as a catalyst to replace peroxidases and as an effective filter for red blood cells in situ to avoid their interferences. The MOG exhibited good peroxidase-like activity with the Michaelis–Menten constant (Km) of 0.5 mM and high affinity toward 3,3′,5,5′-tetramethylbenzidine (TMB) as a chromogenic agent. With such MOG, H2O2 produced from metabolites by their corresponding oxidases can oxidize TMB to generate a colored product, ox-TMB, for quantification with a smartphone. We demonstrated the MOG-μPAD to be sensitive, biomarker-specific, cost-effective, easy-to-use, and stable for storage. We further developed the MOG-μPAD with multiple sensing regions for simultaneously detecting multiple blood biomarkers such as glucose, uric acid, xanthine, and creatinine to monitor numerous metabolic disorders in one run. This offers a new multiplex POCT strategy for detecting the pathogenesis, progression, and prognosis of multiple diseases concurrently, which can be expanded to quantify other biomarkers.