Weaponized Gold Nanotubes Image and Destroy Cancer Cells

Applications May Include Imaging and Treatment

Gold nanoparticls planned to detect and kill cancer cells.

Did you ever marvel at what happens when you press a flashlight to your hand at night? It glows like a jack-o-lantern. That’s because human cells and tissues allow certain frequencies of light to pass through. Once inside, light gets scattered this way and that, depending on what it hits.

Cells can also be quite good at absorbing visible light when it falls on certain structures within, such as packages of melanin or hemoglobin, for instance.

So beams of light and lasers can definitely reach cells that are beneath the skin. And this concept is at the crux of many different ideas and technologies, including the use of gold nanotubes.

Smaller Than Cells, and Adjustable

Gold nanotubes are extremely small cylinders made of gold. Professor Steve Evans at Leeds University and colleagues first reported they had had success controlling the lengths of these nanotubes. Adjustable length turns out to be very useful for medical applications. In this case, the tubes become just the right dimensions to absorb near infrared light or NIR light.

Expert at Absorbing Energy

Evans and colleagues used a laser beam to deliver energy to the gold nanotubes. When the nanotubes absorbed the NIR light, they rapidly heated up so as to become hot enough to destroy nearby cancer cells in mice. NIR light penetrates to a good depth into the tissue, so it's believed that many different types of tumors might be targeted and destroyed in this way.

Like Tuning Forks and Guitar Strings

When a metallic tuning fork vibrates at just the right frequency, the corresponding guitar string starts vibrating at the same frequency. Sound is energy, and so is light. The energy absorbed by the nanotubes can result in heat and sound.

It turns out that the laser can be dialed back a few notches to execute another useful function—diagnostic imaging.

By adjusting the brightness of the laser pulse, Evans and colleagues say that they could use the nanotubes to either destroy cancer cells or image tumors.

  • Killing the cancer cells is referred to as photothermal ablation.
  • Imaging of the cancer using nanotubes as imaging probes makes use of something called photoacoustic signaling.

Here's how photoacoustic signaling works: When a material absorbs pulsed light from a laser, sound waves form due to pressure changes. Special sensors then detect these waves. So, if the gold tubes were set up to accumulate in tumors, the extent of the tumor could then be visualized based on the signal given off by the tubes.

So far, this research group has tested this kind of application in mice. They used something called multispectral optoacoustic tomography (MSOT) to detect the gold nanotubes in colorectal cancer cells in mice. And, because the nanotubes are hollow in the center, researchers believe that they might also serve as vehicles--tiny freight cars, if you will, packed with cancer-killing medication.

A Word from Dr. Ye and Colleagues

Dr. Sunjie Ye from the Molecular and Nanoscale Physics group at the School of Physics and Astronomy at the University of Leeds notes, "This work has developed a route for synthesizing gold nanotubes with controlled length and tunable absorption in the near-infrared region. It represents the first in vitro and in vivo study of gold nanotubes and demonstrates their effectiveness as novel agents as novel agents for multispectral optoacoustic tomography and photothermal therapy with further potential for targeted drug delivery."

Dr. Ye and colleagues would also like to acknowledge Dr. Louise Coletta's Group in the Leeds Institute for Biomedical and Clinical Sciences, Dr. James McLaughlan (School of Electronic & Electrical Engineering) and Dr. Tim Devling (Ithera Medical, German) for their role in this ongoing endeavor.

Bottom Line

These techniques are just beginning to be explored in laboratories, using animals. But there is hope that such work and other emerging innovative techniques might be developed further for use against cancers that fail to respond to currently available therapies.

Sources and Background on Gold Nanotubes in Cancer Research

Ye S, Evans SD et al. Engineering gold nanotubes with controlled length and near-infrared absorption for theranostic applications. Adv. Funct. Mater. 2015;

Sandell JL, Zhu TC. A review of in-vivo optical properties of human tissues and its impact on PDT. Journal of Biophotonics. 2011;4(11-12):773-787.

Gold nanotubes launch a three-pronged attack on cancer cells. http://www.leeds.ac.uk/news/article/3662/gold_nanotubes_launch_a_three-pronged_attack_on_cancer_cells Accessed March 2015.

CNN. Will nanotechnology soon allow you to 'swallow the doctor'? http://www.cnn.com/2015/01/29/tech/mci-nanobots-eth/ Accessed March 2015.

Huang Z, Xu H, Meyers AD, et al. Photodynamic therapy for treatment of solid tumors – potential and technical challenges. Technology in cancer research & treatment. 2008;7(4):309-320.

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