Chemists find new cancer treatment

By Johanna Ohm     11/30/11 6:00pm

Curing cancer has long been a lofty goal of scientific researchers and one that researchers in the Rice University Department of Chemistry have made promising strides toward achieving in recent months.

Rice chemists' success in loading nanorod particles into cancer cells promises new developing treatment options for cancer patients. Research conducted by Associate Professor of Chemistry Eugene Zubarev, graduate student Leonid Vigderman and former graduate student Pramit Manna has focused on developing ways to squeeze up to 2 million gold nanorod particles into a single cancer cell, which could allow scientists to selectively activate the particles and destruct cancer cells from within.

Their findings were published in Angewandte Chemie earlier this month.

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"Nanorod particles have interesting optical properties and are a fairly new area of research," Vigderman said. "Nanorods scatter light, so you can see them when they are collectively together, which is good for imaging, and their photothermal property of turning light into heat offers potential for cancer treatment."

Implications for cancer treatment would involve targeting low-beam laser light on cancer cells that have been injected with nanorods. The light would induce the nanorods to produce heat, generating enough thermal energy to "cook" the cancer cells, effectively killing the cells and preventing metastases.

Vigderman has been researching gold nanorods as part of his doctoral work since his arrival at Rice four years ago, and his topic of interest has proven to be a breakthrough area in nanotechnology research. His recent success in loading nanorods into cancer cells has eliminated one barrier toward the prospective use of nanorods in cancer treatment.

The biological implications of his research, however, were not in his original research plans.

"I'm a chemist," Vigderman said. "My research wasn't originally focused on biological applications. I started with nanorods right away, but the core research I do is how to functionalize the surface of the nanorod. I only saw the potential for a biological purpose later on."

Vigderman says the knowledge that nanorods could be used for eradicating cancer is not exactly a new idea, and has been tried in other labs around the country. What is new about his research is the sheer number of nanoparticles he and collaborators have been able to induce cells to uptake and the method of eliminating toxic surfactants to prevent toxic effects on surrounding cells.

Rice research into gold nanorod particles began with funding from the National Science Foundation a few years ago. After studying basic characteristics of the nanorods, Zubarev said it became important to find real-world applications for the particles.

"That's how we made this connection to cancer treatment," Zubarev said in an online video covering the research project earlier this month.

Prior to the successful uptake of nanorod particles by cancer cells, researchers were facing difficulties in how to get the gold-based particles to dissolve in solution without adding solvents that could be toxic to healthy human cells. The Rice chemists succeeded in dissolving the gold particles and forcing them into cancer cells via development of a new method using a surfactant called MTAB in replacement of the traditionally used CTAB. CTAB is commonly known for its use in hair conditioners and works like most surfactants by coating particles, allowing them to dissolve into a solution. CTAB is toxic to animals, likely because of its propensity to leak into media surrounding cells rather than remaining contained within regions of nanorod localization.

"Nanorods can't be synthesized without CTAB," Vigderman said. "They just won't grow. We knew CTAB was toxic, so we had to make a surfactant that was similar in structure but had a higher affinity for nanoparticles and would not leach into surrounding media where it could be harmful to surrounding cells."

Their solution: MTAB, a molecule chemically similar to CTAB but with a greater affinity for the nanorods and thus less likely to leak outside of the cancer cells targeted for destruction. The paper published this month reported their success in using MTAB for nanorod synthesis and effective elimination of toxic CTAB from tissues that previously scientists were unable to eliminate.

Thus far, the Rice research team has only focused on cell culture studies, which is not always indicative of how live organisms will respond to treatment with nanorods.

"We would like to try the photothermal therapy in tissues," Vigderman said, speaking of the next stages of his research.

Vigderman said that though he is excited for future experiments to test the effectiveness of nanorod cancer therapies, he remains confident that nanorods also have potential for further applications outside of biomedical uses.

"I think, in the future, nanorods could even be used in photovoltaics or for new energy sources," Vigderman said. The optical and thermal properties of nanorods offer varied opportunities of future research for Vigderman to pursue in his continued career at Rice and beyond, as he hopes to graduate and work in industry.

The original research article published in Angewandte Chemie reporting the findings of Vigderman, Manna and Zubarev can be found online at http://onlinelibrary.wiley. com/doi/10.1002/anie.201107304/suppinfo. A video posted by Rice Media containing interviews with the researchers and a view of the lab where the research is being conducted can be found at http://www.media.rice.edu/media/NewsBot.asp?MODE=VIEW&ID=16467.

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