Enzyme catalyzed metallic nanoparticle synthesis and the electrochemical characterization of the glutathione reductase-gold nanoparticle complex

In a novel form of biomimetic nanoparticle synthesis, the mechanism of an FAD-dependent enzyme, glutathione reductase (GR), is harnessed to catalyze the NADPH-dependent reduction of AuCl4- and PtCl 62- to form nanoparticles in the active site of the enzyme. GR's relatively deep active site stabilizes very small metallic clusters and prevents them from aggregating in the absence of a capping ligand. Solid-phase glutathione reductase catalyzed synthesis of gold nanoparticles is demonstrated and proposed as a means to large-scale production of a variety of unique nanoparticle structures. Electrochemical characterization of the GR-gold nanoparticle complex reveals an improved contact between the enzyme's active site and a graphite electrode. This improvement is shown to be due to the nanoparticle in the enzyme's active site. Thioredoxin reductase and lipoamide dehydrogenase are also examined for their ability to reduce AuCl4- and PtCl62- and are compared to GR.