Formation of Growth-Mediated Gold Nanoflowers: Roles of the Reducing Agent and Amine-Modified, Single-Strand DNA Sequences.

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The formation of growth-mediated structures from gold nanoparticle seeds was studied in the presence of amine-modified single-strand DNA sequences and reducing agents such as hydroxylamine and hydroquinone. In the case of hydroxylamine, spherical gold nanoparticle seeds (0.45 nM) were incubated with amine-modified single-strand DNA probes PMR (amine-5'-ACATCAGT-3') and PML (amine-5'-GATAAGCT-3'), which resulted in gold nanoflowers and nanospheres, respectively. When the concentration of the nanoparticle seeds was varied (0.15-0.45 nM), only the PMR sequence showed growth-mediated development of gold nanoflowers. The size of the gold nanoparticles obtained is independent of the seed concentration for both PMR and PML sequences. In contrast, in the presence of the reducing agent hydroquinone, the growth processes are identical in for both the sequences. At a lower seed concentrations (0.15 nM), gold nanoflowers of larger size were observed for both sequences, whereas at higher seed concentrations (0.45 nM), much smaller gold nanospheres resulted. The formation and stability of nanoflowers and nanospheres for PMR and PML with hydroxylamine-based reduction were further studied in detail with diverse controlled amine-modified (5'-, 3'- and both end-modified) and non-modified DNA sequences with other mutants of these two sequences.