Gold nanosponges: Green synthesis, characterization, and cytotoxicity

A simply approach for the synthesis of Au nanostructures in tea infusions at room temperature is developed. By controlling the concentrations of tea infusions, Au nanostructures in various shapes and sizes have been prepared. From 1× (original concentration) and 0.01×(100 times diluted) tea infusions, 52.2±8.1 nm Au nanosponges (T-Au NSs) and 23±2 nm spherical Au nanoparticles (T-Au NPs) were prepared. The phytochemicals present on the surface of T-Au NSs were proved by surface-assisted laser desorption/ionization mass spectrometry, Fourier transform infrared spectrometry and capillary electrophoresis coupled with UV detection. The energy-dispersive X-ray spectroscopy and powder X-ray diffraction data reveal pure crystalline structures of the T-Au NSs. The dark field scattering images observe that the T-Au NSs have significant affinity toward HeLa cells. The cytotoxicity of T-Au NSs on HeLa cells is through caspase-3 activation.