We report on the encapsulation of enzyme (catalase) by the controlled polymer multilayer coating of biocrystals, achieved by the sequential adsorption of oppositely charged polyelectrolytes onto enzyme crystal templates. An extremely high enzyme loading in each polymer capsule is obtained, and the activity of the encapsulated enzyme is preserved. The polymer-encapsulated enzyme is stable against protease degradation:  The polymer-coated enzyme retains 100% of its activity after incubation for 100 min with protease, whereas uncoated, solubilized catalase loses more than 90% of its initial activity within 100 min under the same conditions. This simple, general, and versatile approach can potentially be applied for the encapsulation of various crystallized substances for catalysis and drug delivery applications.

Silver nanodendrites are synthesized by a simple surfactant-free method using a suspension of zinc microparticles as a heterogeneous reducing agent. Structural characterizations suggest the preferential growth along 100 and 111 directions by oriented attachment of silver nanocrystals in the diffusion limit, leading to the formation of silver nanodendrites 20-30 nm in stem and branch diameter and 5-50 microm in length. Surface-enhanced Raman scattering studies show that the silver nanodentrites give an intensive and enhanced Raman scattering when pyridine was used as a probing molecule. We have also demonstrated that the silver nanodendrites increase the sensitivity of an electrochemical glucose biosensor by as much as 1-2 orders of magnitude.