Peptide-covered iron nanoparticles home in on cancerous tumors

William Atkins
Tuesday, 30 January 2007 05:39

Science - Health

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Erkki Ruoslahti and other colleagues from the Burnham Institute for Medical Research in La Jolla, California injected iron nanoparticles covered with a peptide that recognizes clotted plasma proteins into mice infected with human breast cancer. The nanoparticles traveled inside the tumors where they bonded together to eventually block about 20% of the blood vessels inside the tumors. Using magnetic resonance imaging (MRI), Ruoslahti’s team verified that iron clumps containing fluorescent molecules had collected within the tumors.

MRI is a medical imaging technique that obtains images of the body’s soft tissues with the use of electromagnetic radiation.

The MRI scans found that the nanoparticles showed up three times brighter than when the particles were not amplified with the fluorescence. Being able to image the amount of nanoparticles delivered to the cancerous tumor is critical in diagnosing and treating cancer. In fact, Ruoslahti also sent liposomes—miniscule liquid-filled sacs consisting of fat molecules—into tumors instead of iron-oxide nanoparticles. Liposomes can be used to carry cancer drugs while iron-oxide nanoparticles are used to diagnose cancer.

The researcher’s experimental results (“Biomimetic amplification of nanoparticle homing to tumors”) were reported in the January 16, 2007 issue of The Proceedings of the National Academy of Sciences. Within the article, the collaborators state, “The self-amplifying homing is a novel function for nanoparticles. The clotting-based amplification greatly enhances tumor imaging, and the addition of a drug carrier function to the particles is envisioned.”

Because of these results, the researchers believe that better images for diagnosis can be produced and larger amounts of cancer drugs for treatment can be delivered to tumor sites. Ruoslahti states, “The more particles you get into the tumor, the better images you’re going to get, and the better therapeutic effect you’re going to get if it’s a drug-delivery system.”

In addition, by pinpointing where the cancer-fighting drugs are to be used, the treatment minimizes the drugs’ damaging affects to healthy tissues. Consequently, negative side effects are fewer and less severe when compared to those common with invasive cancer treatments such as surgery and chemotherapy.

The challenge in the future for Ruoslahti and other researchers is to make the technique safe and effective. Currently, the biomimetic amplification process of the nanoparticles can cause blood clots to travel outside the tumor and into critical organs and can cause the accumulation of drugs outside the tumor.

The home Web page of the Burnham Institute for Medical Research is: http://www.burnham.org/.

The PNAS article “Biomimetic amplification of nanoparticle homing to tumors” appears at: http://intl.pnas.org/cgi/content/short/104/3/932.