Colorimetric detection of uric acid based on enhanced catalytic activity of cobalt-copper bimetallic-modified molybdenum disulfide

A method for the quantification of uric acid (UA) by colorimetry using a four-in-one nanocomposite MoS2/PDA/CoCu as a novel nanozyme was proposed. The nanocomposite was prepared based on the deposition of metal cobalt and copper nanoparticles onto the surface of MoS2 nanosheets using polydopamine (PDA) as a stabilizer. The Michaelis-Menten model was used to monitor the catalytic efficiency of peroxidase-like reactions, and the results showed that the Michaelis constant Km (0.0076 mM and 0.0032 mM) values calculated by the Lineweaver-Burk equation were much lower than those of horseradish peroxidase and other reported nanozymes, demonstrating that MoS2/PDA/CoCu has excellent peroxidase-like activity. Theoretically, uric acid can produce allantoin and H2O2 in the presence of uricase and oxygen, respectively. The nanocomposite efficiently catalyzes H2O2 to produce hydroxyl radicals (•OH) that then oxidize colorless 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to the blue oxidation product (ox-TMB) which corresponds to the characteristic absorption peak at 652 nm. Using optimal conditions, we constructed a sensitive visible visual colorimetric method combined with a designed smartphone for UA detection (0.5–200 μM, R2 = 0.995) with a limit of detection (S/N = 3) of 0.13 μM. When UA was detected in serum and urine samples, good recovery rates were obtained, indicating the great potential of this method for the detection of uric acid in clinical and daily life applications.