Catalase-modified gold nanoparticles: Determination of the degree of protein adsorption by gel electrophoresis

[Display omitted] •Gold nanoparticles (AuNPs) with the size of about 13nm modified with catalase.•Stable catalase modified-AuNPs colloids obtained.•Surface coverage of AuNPs with catalase determined.•Gel electrophoresis presented as a fast and versatile method for determination of surface coverage of NPs with protein. In this study we present a method to determine the degree to which catalase (CAT) is adsorbed onto gold nanoparticles (AuNPs) using polyacrylamide gel electrophoresis (PAGE) with silver staining. AuNPs (13nm) were synthesized in water by the chemical reduction method and modified with CAT (AuNPs-CAT). The colloidal stability and NP size before and after the modification were investigated by dynamic light scattering and scanning transmission electron microscopy. Electrophoresis was performed under different conditions (native, with and without SDS, and with and without β-mercaptoethanol) to find the optimal conditions for determining the surface coverage of AuNPs with CAT protein. The results clearly indicate that PAGE can be used to determine the amount of protein adsorbed on the NP surface and the use of native PAGE does not alter the colloidal stability of the NPs. These features allowed us to monitor the state of NPs and protein-NP interactions during the electrophoretic process.