Colorimetric Detection of Sarcosine Based on Peroxidase-like Activity of Fe-based 7-Cyclodextrin Nanoparticles

Fe-based y-cyclodextrin nanoparticles (Fe-y-CD) with peroxidase-like activity were successfully synthesized through a solvothermal approach for establishing a simple and sensitive sarcosine (SAR) assay method. Fe-y-CD could catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) in the presence of H2O2, accompanied by a characteristic absorption peak centered at 652 nm. The effects of reaction conditions were investigated, and the catalytic mechanism as well as the steady-state kinetics were analyzed. Fe-y-CD could catalyze H2O2 2 O 2 to generate hydroxyl radical, singlet oxygen and superoxide radical, these reactive oxygen species with robust oxidizability further oxidized TMB. This process followed a typical MichaelisMenten kinetic model. With the assistance of sarcosine oxidase (SOx), SAR was hydrolyzed into H2O2 to trigger Fe-y-CD catalyzed chromogenic reaction, resulting in deepened color and increased absorbance. The degree of colorimetric signal change was related to SAR concentration and thus SAR could be quantitatively detected. The linear range and detection limit were 1.0-70.0 mu mol/L and 0.46 mu mol/L, respectively. Typical amino acids and metal ions had no obvious interference on SAR detection, indicating a good selectivity. The method was to determination of SAR level in serum with results.