The researchers found that the amplification also worked when they used liposomes–tiny liquid-filled spheres made of fat molecules–instead of iron-oxide nanoparticles. That means the self-amplifying process depends on the peptide, and the researchers could use different nanoparticles for various functions. For instance, the magnetic iron-oxide nanoparticles that they use could be employed for diagnosing cancer in humans, because they are popular MRI image-enhancing agents. Liposomes, on the other hand, could be used to carry cancer drugs. “The novelty here is the self-amplification,” Farokhzad says. “The technology would be applicable to just about any other nanoplatform that we use for tumor targeting, whether for imaging or therapeutic purposes.”
Ruoslahti also plans to test other similar peptides that could cause clotting in much more than 20 percent of the blood vessels to choke off the tumor’s oxygen supply.Making the technique safe and effective will take a lot more work. When injected into mice, the peptide-coated nanoparticles trigger an immune response, and the liver tries to get rid of them. The researchers currently avoid this by injecting a decoy particle to take the immune system’s attention away from the peptide particles. But to be efficient, “we should be able to engineer a nanoparticle that does what we need it to do without the help of other nanoparticles,” Farokhzad says.
Hayat Onyuksel, a pharmaceutics and bioengineering professor at the University of Illinois at Chicago, says that the main safety challenge would arise from precisely what makes this new work exciting: self-amplification. It would be crucial to localize the nanoparticles inside tumors so that they do not cause clots in the liver, lungs, and other organs, and so that drug-carrying nanoparticles do not accumulate in the organs, she says.
It would also be important to control the clotting that the peptides induce inside tumor blood vessels, Amiji says, because the clots could dislodge from the vessels and enter into the brain, heart, or other areas. “As long as you can keep the clots in the tumor, this is a very elegant concept.”