Urease-Functionalized Near-Infrared Light-Responsive Gold Nanoflowers for Rapid Detection of Urea by a Portable Pressure Meter

Urea is one of the leading products produced by protein degradation in human body. The levels of urea could be used as an important indicator of health status and renal disease. Thus, portable, rapid, and convenient point-of-care testing systems are highly in demand. Herein, urease-functionalized near-infrared (NIR) light-responsive gold nanoflowers (AuNFs) served as a sensing platform for urea assay. The urease-AuNFs composites were constructed via electrostatic interaction and possessed strong photothermal effect. The 808 nm laser irradiation heated the urease-AuNFs composites, which increased urease activity and accelerated the catalytic decomposition of urea. The generated NH3 and CO2 caused pressure changes, which could be recorded by a pressure meter. The pressure changes were proportional to the concentrations of urea ranging from 1 mM to 100 mM, and the detection limit of 0.08 mM was achieved. The urea in blood samples could be conveniently measured in 10 min and the urea levels were in good agreement with the clinical results. The NIR light-responsive AuNFs could find broad applications for clinical point-of-care testing of other diseases-related indicators.