Portable paper-based sensing device by bimetallic layered hydroxide immobilization for visual analysis of uric acid on a smartphone platform

Uric acid (UA) is an important biomarker for assessing human health. The abnormal contents of UA in biological fluids are closely involved with many diseases. Although conventional methods for UA analysis with satisfied detection performances have been well-designed, they are still restricted by bulky instrument requirements and insufficiency during the detection processes. Herein, we have built a cellulose paper-based nanozyme detection platform (CF-cPADs) by immobilizing the cobalt-iron layered double hydroxide (CoFe LDH) for point-of-care (POC) detection of UA. In this assay, CoFe LDH with peroxidase (POD)-like activity has been synthesized to be immobilized onto the cellulose paper, and then the uricase (Uox) and CoFe LDH involved cascaded enzymatic reaction has been designed to realize the conversion from UA contents to colorimetric signals, which can be further analyzed by smartphone. The highly sensitive, stable, and reproducible CF-cPADs exhibit a wide linear range varied from 1 to 100 μM with a comparable limit of detection (LOD) as low as 0.92 μM for satisfying UA analysis in real samples. This approach can provide new insights into the development of cost-effective, portable, rapid, easy-to-use, and on-site detection of biomarkers. It will overcome the drawbacks in clinical diagnosis which are highly dependent on the professionals and analytical instruments.