Gold nanoparticles carrying diatomic molecules (O2 and CO) in aqueous solution

Gold nanoparticles (AuNPs) prepared by citrate reduction of aurochloric acid (HAuCl(4)) were functionalized by tris(4-sulfonatophenyl)porphinatoiron(III) (Fe(III)P2) and poly(ethylene glycol) with thiolated arms (PEG-SH). Fe(III)P2 on the AuNP surface existed as its μ-oxo dimer, which was reduced by Na(2)S(2)O(4) to yield monomeric Fe(II)P2. Fe(II)P2-bearing AuNPs were further functionalized through inclusion of two sulfonatophenyl groups of Fe(II)P2 by a per-O-methylated β-cyclodextrin dimer with a pyridine linker (Py3CD) to obtain AuNPs capable of carrying diatomic molecules in the body. The resulting AuNPs (hemoCD-AuNPs) bound O(2) as well as CO in an aqueous solution. Although a noncolloidal 1:1 complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(II) and Py3CD injected into the femoral vein of a rat was rapidly excreted in the urine, no excretion was observed with ferric hemoCD-AuNPs, which were gradually accumulated in the spleen and liver of a rat. These results suggest that hemoCD-AuNPs can be used as a carrier of diatomic molecules such as O(2) and CO in vivo.