Cambridge, Mass - The problem with treating tumors using heat is that it's easy to destroy neighboring tissue as well. But MIT researchers have developed a way of keeping the heat confined to where it's needed.
Tiny gold particles, known as nanorods, can home in on tumors, and then, by absorbing energy from near-infrared light and emitting it as heat, destroy tumors with minimal side effects.
In the study, tumors in mice that received an intravenous injection of nanorods plus near-infrared laser treatment disappeared within 15 days. Those mice survived for three months with no evidence of reccurrence, while mice that received no treatment or only the nanorods or laser did not.
The nanorods could diagnose as well as treat tumors, says MIT graduate student Geoffrey von Maltzahn, who developed the tumor-homing particles with Sangeeta Bhatia, professor in the Harvard-MIT Division of Health Sciences and Technology and in the Department of Electrical Engineering and Computer Science.
While chemotherapy is a blunt-edged tool, say the researchers, the gold nanorods can specifically focus heat on the right spot. "This class of particles provides the most efficient method of specifically depositing energy in tumors," von Maltzahn claimed.
Once the nanorods are injected, they disperse uniformly throughout the bloodstream. But blood vessels located near tumors have tiny pores just large enough for the nanorods to enter, and they accumulate in the tumors. Within three days, the liver and spleen clear any that don't reach the tumor.
During a single exposure to a near-infrared laser, the nanorods heat up to 70 degree Celsius, hot enough to kill tumor cells. In addition, heating them to a lower temperature weakens tumor cells enough to enhance the effectiveness of existing chemotherapy treatments.
The nanorods could also be used to kill tumor cells left behind after surgery. The nanorods can be more than 1,000 times more precise than a surgeon's scalpel, says von Maltzahn, so they could potentially remove residual cells the surgeon can't get.
The nanorods' homing abilities also make them a promising tool for diagnosing tumors. After the particles are injected, they can be imaged using a technique known as Raman scattering. Any tissue that lights up, other than the liver or spleen, could harbor an invasive tumor.
Bhatia and von Maltzahn are looking into commercializing the technology. Before the gold nanorods can be used in humans, they must undergo clinical trials and be approved by the FDA, which von Maltzahn says will take some years.