Biotechnology

Biography

Biography: Tatsuki Kunoh

Abstract

So-called “green” synthesis of safe metal nanoparticles, especially gold nanoparticles (AuNPs), has increased in importance for medical and pharmaceutical applications; thus, a variety of ecofriendly, energy- and cost-saving techniques have been developed. Here we show that RNA prepared from Leptothrix (iron-oxidizing bacteria) cells can reduce Au(III), and spherical AuNPs eventually form when an aqueous solution of Au chloride (HAuCl₄ Soln) is added under ambient conditions. RNA and DNA of other organismal origins have the same ability. Of the nucleosides and nucleobases, only guanosine and guanine can form AuNPs. The DNA moiety, 2'-deoxyguanosine (dG) (used as a reference material), forms AuNPs when mixed with HAuCl4 Soln, but 8-hydroxy-2'-deoxyguanosine (8-OHdG) does not, indicating that AuNP-formation evidently depends on the reduction potential of the guanine moiety, not the sugar moiety. This finding is the first demonstration that spherical AuNPs of ca. 5 nm diameter can be obtained by simply adding guanine to HAuCl₄ Soln at ambient temperature; no other chemicals or physical treatments are needed.