Enzymes within Gold Nanoaggregate Cages

The integration of metals with organic compounds offers an assortment of new composite materials, denoted as dopant@metal, that merge the characteristics of the metal with those of the organic compound. Some of the composite materials exhibit synergism in their action – such as bactericidal effects in biomolecule@Ag, corrosion resistance in iron composites and more. So far, the library of entrapped dopants was mainly limited to small organic molecules and polymers. In this research, this family of materials is expanded to include enzymes. We report the successful solution to the challenge of incorporating enzymes within metals, specifically gold. The synthetic process is based on the reduction of the metal salt in presence of the enzyme, which results in a gold aggregate of nanometric crystallites, such that enzyme is physically held within open cages. The challenge has been to conduct that process under conditions which allow the enzyme to retain its catalytic activity. Preliminary results indicate that the obtained composite materials indeed maintain the ability to perform the enzyme’s catalytic reaction, while providing the enzyme with protection against non-optimal environmental conditions. Moreover, in some cases, the entrapment of the enzyme within gold brings about new properties, such as activity on non-native substrates. Specifically, L-asparaginase, collagenase, glucose oxidase and achromopeptidase were successfully entrapped within gold. Full characterization of the materials properties and of the enzymatic activity is provided.