An international team of collaborators from a number of academic institutions and a couple pharmaceutical firms has been working with researchers at the National Institute of Standards and Technology (NIST) to study how special sugar coated iron oxide nanoparticles interact with each other to destroy cancer cells under laboratory conditions. The 100 nanometer wide particles, which are attracted by tumor cells, are particularly prone to magnetically induced heating.
Minuscule balls of iron oxide can be coated with sugar molecules making them particularly attractive to resource-hungry cancer cells. Once the particles are injected, cancer cells would then ingest them, and doctors would then be able to apply an alternating magnetic field that causes the iron oxide centers to heat, killing the cancer but leaving surrounding tissue unharmed.
Two biotech companies, Micromod Partikeltechnologie and Aduro BioTech, created particles that showed great potential in treating cancers in mice, and they asked NIST to help understand why it worked so well. “But they sent us particles that were much larger than what the conventional wisdom says they should be,” says NIST materials scientist Cindi Dennis. “Larger particles are more strongly magnetic and tend to clump together, which makes them large enough to attract the body’s defense systems before they can reach a tumor. The companies’ nanoparticles, however, did not have this problem.”
Neutron scattering probes at the NIST Center for Neutron Research revealed that the particles’ larger iron oxide cores attract one another, but that the sugar coating has fibers extending out, making it resemble a dandelion—and these fibers push against one another when two particles get too close together, making them spring apart and maintain an antibody-defying distance rather than clumping. Moreover, when the particles do get close, the iron oxide centers all rotate together under the influence of a magnetic field, both generating more heat and depositing this heat locally. All these factors helped the nanoparticles destroy breast tumors in three out of four mice after one treatment with no regrowth.
Side image: When tumor cells ingest them, the particles still congregate closely enough to share heat when stimulated by a magnetic field, killing the cells. White arrow indicates a red blood cell.
Press release: Therapeutic Nanoparticles Give New Meaning to Sugar-Coating Medicine…
Abstract in Nanotechnology: Nearly complete regression of tumors via collective behavior of magnetic nanoparticles in hyperthermia