A simple and versatile method for the preparation of functional enzyme-gold nanoparticle conjugates using "click" chemistry has been developed. In a copper-catalyzed 1,2,3-triazole cycloaddition, an acetylene-functionalized Thermomyces lanuginosus lipase has been attached to azide-functionalized water-soluble gold nanoparticles under retention of enzymatic activity. The products have been characterized by gel electrophoresis and a fluorometric lipase activity assay. It is estimated that the equivalent of approximately seven fully active lipase molecules are attached to each nanoparticle.

A rationally designed peptide and a thioalkylated poly(ethylene glycol) are used to stabilize Ag nanoparticles in water. Particle aggregation and oxidation are prevented to such a degree that nanoparticle solutions are stable in the presence of high concentrations of NaCl and over a wide pH range. This opens the door for the use of Ag nanoparticles in biological applications.

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