Mesoporous ZnS nanorattles: programmed size selected access to encapsulated enzymes

A size selective nanorattle was formed by encapsulating soybean peroxidase (SBP) within a ZnS mesoporous hollow sphere. Once encapsulated within the mesoporous hollow sphere, the SBP remained active against molecules smaller than the 3 nm diameter of the mesopores in the shell wall, while molecules larger than the mesopores, which could not pass into the hollow sphere, did not interact with the SBP. Specifically, encapsulated SBP catalyzed the oxidation of Amplex Ultra-Red, a small fluorogen, in the presence of hydrogen peroxide, encapsulated SBP was deactivated by sodium azide, and no reaction was observed between encapsulated SBP and a greater than 3 nm diameter protease.