Intracellular synthesis of gold nanoparticles with antioxidant activity by probiotic Lactobacillus kimchicus DCY51 T isolated from Korean kimchi

A straightforward synthesis of gold nanoparticles (AuNps) is achieved by novel probiotic Lactobacillus kimchicus DCY51T isolated from Korean kimchi via an intracellular membrane-bound mechanism. The bioreduction of HAuCl4 into AuNps was verified by ultraviolet-visible spectrophotometry at ∼540nm. AuNps were spherical with varying sizes of 5-30nm. AuNps maintained an average crystallite size of 13nm and demonstrated long-term stability in physiological buffer and biological media. Furthermore, the protective capping layer consisted of amino acid residues and surface-bound proteins rendered them non-toxic to murine macrophage (RAW264.7) and human colorectal adenocarcinoma (HT29) cell lines. Finally, biosynthesized AuNps served as superior free radical scavengers against 2,2-diphenyl-1-picrylhydrazyl (DPPH) in contrast to their corresponding gold salt. In short, this green synthesis is cost-effective and advantageous for the development of a new class of probiotics mediated and non-toxic carriers in targeted drug delivery systems, cancer diagnostic, photothermal therapy, biosensing, and medical imaging.