Analytical Sciences

Biocatalytic Formation of Gold Nanoparticles Decorated with Functional Proteins inside Recombinant Escherichia coli Cells

Yukiho HOSOMOMI,* Teppei NIIDE,** Rie WAKABAYASHI,* Masahiro GOTO,*,*** and Noriho KAMIYA*,***

*Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
**Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba, Sendai 980-8579, Japan
***Center for Future Chemistry, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan

A novel strategy for the preparation of protein-decorated gold nanoparticles (Au NPs) was developed inside Escherichia coli cells, where an artificial oxidoreductase, composed of antibody-binding protein (pG), Bacillus stearothermophilus glycerol dehydrogenase (BsGLD) and a peptide tag with gold-binding affinity (H₆C), was overexpressed in the cytoplasm. In situ formation of Au NPs was promoted by a natural electron-donating cofactor, nicotinamide adenine dinucleotide (NAD), which was regenerated to the reduced form of NADH by the catalytic activity of the fusion protein (pG-BsGLD-H₆C) overexpressed in the cytoplasm of E. coli, with the concomitant addition of exogenous glycerol to the reaction system. The fusion protein was self-immobilized on Au NPs inside the E. coli cells, which was confirmed by SDS-PAGE and western blotting analyses of the resultant Au NPs. Finally, the IgG binding ability of the pG moiety displayed on Au NPs was evaluated by an enzyme-linked immunosorbent assay.

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