Glimpse of single ultrasmall gold nanorods inside cells
doi:10.1038/nindia.2014.117 Published online 26 August 2014
Researchers have gained new insights into the three-dimensional rotational dynamics and optical properties of single ultrasmall gold nanorods in chemical solutions and inside human embryonic kidney cells1. These insights will help better understand the molecular reactions that occur in intracellular environments.
Existing techniques have been used to probe small gold nanorods, but they are not suitable for exploring the properties of ultrasmall gold nanorods (average length of 30 nm and an average diameter of 10 nm). The researchers used polarized dark-field-scattering micro-spectroscopy to explore the three-dimensional rotational dynamics and optical properties of ultrasmall gold nanorods in viscous polyethylene glycol solutions and the nanorods’ interactions with biological molecules inside human embryonic kidney cells.
The researchers found that the observable rotational dynamics of the nanorods lasted from microseconds to seconds in the viscous solutions. They found that the possible adsorption of polyethylene glycol on the surface of nanorods increased surface plasmon resonance — light-induced collective oscillations of electrons on the surfaces of the nanorods.
To track the path of gold nanorods inside the cells, the researchers attached transferrin-conjugated gold nanorods to the cell membrane. This led to a sharp surface plasmon resonance at a wavelength of 600 nm, indicating the presence of single gold nanorods. They found that the nanorods moved in a constricted environment between the nucleus and the cell membrane.
In addition, they found that the nanorods fused with cellular vesicles. This fusion of vesicles and the nanorods increased the scattering of light. The nanorods took 7 minutes to bind to the cell-surface proteins and penetrate the cell membrane and less than 3 minutes to travel towards the interior of the cell and back to the cell membrane.
The researchers say that combining this technique with a real-time signal-controlled microscope will be useful for tracking intracellular components labelled with gold nanorods.
1. Chaudhuri, K. et al
. Spatiotemporal mapping of three dimensional rotational dynamics of single ultrasmall gold nanorods. Sci. Rep.
4, 5948 (2014) doi: 10.1038/srep05948