The color image of the kit was captured by a smartphone built-in camera and converted into color intensity using ImageJ software, thus achieving the quantitative determination of UA. 
ImageJ
CuCo2S4 nanozyme-based stimulus-responsive hydrogel kit for rapid point-of-care testing of uric acid.An efficient analysis platform composed of nanozyme-based hydrogel kit and smartphone was constructed for on-site detection of uric acid (UA) in a rapid and realiable manner.  CuCo2S4 nanoparticles (CuCo2S4 NPs) as a peroxidase mimic were successfully prepared and the peroxidase-like activity and catalytic mechanism were studied in detail.  The hydrogen peroxide (H2O2) stimulus-responsive nanozyme-based hydrogel kit was manufactured by integrating agarose, CuCo2S4 NPs, and 3,3',5,5'-tetramethylbenzidine (TMB) into the cap of centrifuge tube.  H2O2 generated via UA oxidation acts as stimulus signal, which triggers the oxidation of TMB to form blue product (oxTMB) under the catalysis of CuCo2S4 NPs, resulting in the color response of the constructed kit.  The color image of the kit was captured by a smartphone built-in camera and converted into color intensity using ImageJ software, thus achieving the quantitative determination of UA.  The portable kit possesses high selectivity and was used to monitor UA in human serum with satisfactory results (recovery was in the range 95.8-107.3% and RSD was not greater than 4.6%).  The established sensing platform is convenient and reliable, which provides a new strategy for point-of-care testing of UA and has a broad prospect in the fields of chemical sensing and biomedical.
C