The study shows that in principle, gold nanoparticles can intensify the killing power of radiation on cancer cells.
Writing in the Proceedings of the National Academy of Sciences, a team from Brown University in Providence and the University of Rhode Island in Kingston, RI, says their proof-of-concept study could lead to improved cancer treatments.
Treatments could be improved in two ways: either by using less radiation, thus reducing adverse effects to patients, or by boosting the ability of current doses to kill more cancer.
Nanotechnology is a relatively new and growing field where scientists can manipulate nanometer-sized materials (nanoparticles) and tools that operate at the scale of individual cells.
Previous studies have already shown that because of their unique properties, gold nanoparticles can increase the effectiveness of radiation in killing cancer cells.
The gold nanoparticles act like tiny antennas that concentrate the radiation in the area around them.
pHLIPs deliver gold nanoparticles right up to cancer cells
In this study, the team showed that using acid-seeking compounds called pH low-insertion peptides (pHLIPs) to deliver the gold nanoparticles right up to cancer cells, they substantially increased the power of radiation to kill them.
The pHLIPs are important because they seek out the slightly more acidic malignant cells and take the gold nanoparticles right up to them and tether them to their cell membranes. The nanoparticles can only intensify radiation at a close range.
The study extends previous work by others from URI and Yale who invented pHLIP technology. One of these was senior author of the new study Yana Reshetnyak, URI professor in biological and medical physics, who explains the point of the further work:
"We previously demonstrated that pHLIP-nanogold particles could find and accumulate in tumors established in mice. Now our task is to test if we can treat cancer by irradiating tumors with nanogold particles more efficiently in comparison with traditional radiation treatment."
Studies based on theory and experiments show that gold nanoparticles absorb around 100 times more radiation than tissue. Because of gold's unique properties, the radiation causes the particles to release a stream of electrons into their immediate surroundings. If this could happen in and very near cancer cells, they could suffer serious damage.
Irradiated cancer cells had 24% lower survival rate in presence of pHLIP-delivered gold
So in this new study, Prof. Reshetnyak and colleagues decided to bring together the ability of pHLIPs to target cancer cells with the unique properties of gold nanoparticles.
After crunching masses of complex calculations and running experiments, they showed that cancer cells irradiated in the presence of pHLIP-delivered gold had a 24% lower survival rate compared to those treated with radiation alone.
They also found that the pHLIP samples had a 21% lower survival compared to irradiation with just gold but no pHLIPs.
The authors say these findings suggest the pHLIPs were effective in getting the gold close enough to the cancer cells to do damage.
Lead author Michael Antosh, assistant professor of brain and neural systems research at Brown, says:
"This study was a good proof of concept. We're encouraged by our initial results and we're excited to take the next step and test this in mice."
In December 2014, Medical News Today reported a study that suggests most elderly breast cancer patients receive unnecessary radiation. In the journal Nature Methods, the authors say that despite evidence supporting the omission of radiation treatment for elderly female patients with early-stage breast cancer, nearly two thirds of them are still receiving it.