A Photonic Crystal Gel for Naked-Eye Detection of Uric Acid with High Sensitivity and Specificity

Uric acid is a signal molecule that regulates the metabolic activities of the human body, and its abnormally high levels will result in multiple complications. However, the current methods for detecting uric acid generally require high-precision instruments and professional operation. Herein, a redox-responsive photonic crystal (PC) gel for specific detection of uric acid by visualized iridescent colors with high sensitivity is successfully developed by cross-linking N-isopropylacrylamide via both macromolecular poly(ethylene glycol) acrylamide (PEG) and N,N′-cystamine-bis-acrylamide (BAC). By adjusting the PEG and BAC content, the size and concentration of magnetite nanoparticles, and magnetic field strength, the PC gel prepared can specifically detect uric acid levels with the aid of uricase and achieve a color change from orange-red to blue. Such a PC gel has excellent repeatability, and the lowest relative error of uric acid in commercial rabbit serum between the results measured by the gel and enzyme-labeled instrument is merely 6%. This study provides an effective strategy for the visualizing of uric acid in actual urine and blood with high sensitivity and specificity.