Colorimetric detection of urea, urease, and urease inhibitor based on the peroxidase-like activity of gold nanoparticles

Herein, we reported for the first time that gold nanoparticles-catalyzed 3,3′,5,5′-tetramethylbenzidine-H 2 O 2 system can serve as an ultrasensitive colorimetric pH indicator. Gold nanoparticles acted as a catalyst and imitated the function of horseradish peroxidase . The absorbance at 450 nm of the yellow-color product in the catalytic reaction exhibited a linear fashion over the pH range of 6.40–6.60. On the basis of this property, we constructed a novel sensing platform for the determination of urea, urease , and urease inhibitor. The limit of detection for urea and urease was 5 μM and 1.8 U/L, respectively. The half-maximal inhibition value IC 50 of acetohydroxamic acid was found to be 0.05 mM. Urea in human urine and urease in soil were detected with satisfied results.