Methods
i) directly on the surface of AuNPs (non-specific immobilization), and ii) via chemical bonding using a linker (specific immobilization). Quantification of the enzyme amount adsorbed on the nanoparticle surface was determined by native-polyacrylamide gel electrophoresis (native-PAGE). Colloidal stability of AuNPs before and after the enzyme immobilization was monitored with dynamic light scattering (DLS) and UV-vis spectroscopy. The size of the metallic core was determined by scanning-transmission electron microscopy (STEM). The enzymatic activity of catalase immobilized on AuNPs was investigated by antioxidant tests and compared with free (non-immobilized) catalase. It was found that the activity of catalase immobilized on AuNPs is affected by the immobilization method. Moreover, it was found that the non-specific immobilization decreased the antioxidant activity while the specific immobilization of catalase allowed the catalase activity to remain at the same level as that of free catalase.