Nanozyme based on graphene oxide modified with Fe 3 O 4 , CuO, and cucurbit[6]uril for colorimetric determination of homocysteine.

A nanozyme based on graphene oxide modified with Fe ₃ O ₄ NPs, CuO NPs, and cucurbit[6]uril has been successfully fabricated by a simple sonochemical technique. By employing CB[6] as a specific binding pocket and Fe ₃ O ₄ @CuO-GO as a peroxidase mimic, this novel nanozyme (BN I) is equipped with molecular recognition ability and enhanced peroxidase-like activity. On the basis of the inhibition effect of homocysteine (Hcy) towards the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) catalyzed by BN I, a simple colorimetric method is established for the sensitive and selective determination of Hcy. This proposed method displays a good linear response in the range 5-200 μM with a detection limit of 1.8 μM. In the practical assay of human plasma samples, the relative standard deviations (RSD) are lower than 11% and the recoveries are between 98.0 and 104.9%. In the assay of human urine samples, the RSD are below 9.0% and the recoveries range from 94.0 to 103.5%. The colorimetric method presented offers a convenient and accurate way for the determination of biomarkers in point-of-care testing (POCT).