Scientists in the U.K. say their research provides evidence that gold nanotubes have a number of important applications in fighting cancer. These include their use in high-resolution imaging, as cancer drug delivery vehicles, and as therapeutics for destroying cancer cells.

The team reports that their study (“Engineering Gold Nanotubes with Controlled Length and Near-Infrared Absorption for Theranostic Applications”), published in Advanced Functional Materials, details the first successful demonstration of the biomedical use of gold nanotubes in a mouse model of human cancer.

According to lead author Sunjie Ye, Ph.D., who is based in both the school of physics and astronomy and the Leeds Institute for Biomedical and Clinical Sciences at the University of Leeds, “High recurrence rates of tumors after surgical removal remain a formidable challenge in cancer therapy. Chemo- or radiotherapy is often given following surgery to prevent this, but these treatments cause serious side effects.”

Gold nanotubes, that is, gold nanoparticles with tubular structures that resemble tiny drinking straws, have the potential to enhance the efficacy of these conventional treatments by integrating diagnosis and therapy in one single system, added Dr. Ye.

The scientists explain that a new technique to control the length of nanotubes underpins the research. By controlling the length, the researchers were able to produce gold nanotubes with the right dimensions to absorb near infrared light.

The study's corresponding author Professor Steve Evans, from the School of Physics and Astronomy at the University of Leeds, said: “Human tissue is transparent for certain frequencies of light – in the red/infrared region. This is why parts of your hand appear red when a torch is shone through it.

“When the gold nanotubes travel through the body, if light of the right frequency is shone on them they absorb the light,” notes Steve Evans, Ph.D., from the school of physics and astronomy.” This light energy is converted to heat, rather like the warmth generated by the sun on skin. Using a pulsed laser beam, we were able to rapidly raise the temperature in the vicinity of the nanotubes so that it was high enough to destroy cancer cells.”

In cell-based studies, by adjusting the brightness of the laser pulse, the researchers were able to control whether the gold nanotubes were in cancer-destruction mode, or ready to image tumors.

In order to see the gold nanotubes in the body, the researchers used a new type of imaging technique called multispectral optoacoustic tomography to detect the gold nanotubes in mice, in which gold nanotubes had been injected intravenously. It was also shown that gold nanotubes were excreted from the body and therefore are unlikely to cause problems in terms of toxicity, an important consideration when developing nanoparticles for clinical use.

“[Our results] demonstrate that these [gold nanotubes] have the ideal attributes to develop their potential as effective and safe in vivo imaging nanoprobes, photothermal conversion agents, and drug delivery vehicles,” wrote the investigators. “To the best of knowledge, this is the first in vitro and in vivo study of gold nanotubes.”

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