Visualizing nanoparticle mobility in liquid at atomic resolution

bDepartment of Biology, Indiana University at Bloomington, Bloomington, IN 47405, USA
cVirginia Tech Carilion Research Institute, Roanoke, VA 24016, USA. E-mail: debkelly@vt.edu; Fax: +1 540 985 3373; Tel: +1 540 526 2031

Received 11th February 2013, Accepted 28th February 2013
First published on the web 28th February 2013

Gold nanorods are widely known for their photothermal properties to treat solid tumors. Our work demonstrates the unrealized capacity to image these reagents in liquid at high resolution using Transmission Electron Microscopy (TEM). Here we perform the first atomic measurements of functionalized nanorods in solution while visualizing their dynamic behaviour with TEM.

The use of microfluidic-based devices has spurred new opportunities to visualize dynamic mobility at the molecular level.1,2 Using these tools scientists have recently watched, for the first time, the growth of nanocrystals into materials and the engulfment of nanoparticles into cells.3–6 These recent technological advancements in conjunction with high-resolution imaging provide a new opportunity to view nanoscale processes as they occur in solution.

A new mode of therapeutic intervention in cancer research employs the use of rod-shaped gold nanoparticles, appropriately termed “nanorods”. Nanorods injected into the circulation can be engineered to target, infiltrate and accumulate in solid tumors.7,8 Upon applying infrared radiation at the tumor site, the high photothermal conversion rate of the nanorods increase the temperature of the surrounding region to kill off cancerous cells.9,10 Although this application for the therapeutic use of nanorods is gaining popularity, the molecular behavior of these nanoparticles has never been observed. Here we present the first high-resolution view of how polyvinyl pyridine (PVP)-encapsulated gold nanorods migrate in liquid using in situ molecular microscopy. In doing so, we also introduce a novel system to view short-range diffusion properties of nanogold-based therapeutic reagents in a native environment.