Synthesis of biologically stable gold nanoparticles using imidazolium-based amino acid ionic liquids

A novel double-step reduction procedure for the synthesis of gold nanoparticles (AuNPs) using amino acid ionic liquids has been employed. 1-Dodecyl-3-methyl imidazolium tryptophan ([C(12)mim]Trp) and 1-ethyl-3-methyl imidazolium tryptophan ([C(2)mim]Trp) were used for this synthesis. The synthesized AuNPs were characterized by UV-vis spectroscopy, transmission electron microscopy and dynamic light scattering. The behavior of these AuNPs were also probed in a biological media. It was proven that AuNPs synthesized at [C(12)mim]Trp have more stability than AuNPs synthesized at [C(2)mim]Trp due to the longer alkyl chain of the imidazolium moiety. The solubility test shows that the resultant AuNPs have a hydrophilic nature. Finally, it was seen that due to the presence of a biomolecule, namely Trp, in the structure of AuNPs protecting shell, higher stability and biocompatibility was achieved in the biological media.