29 August 2011

from NatureAsia Website

Illustration of core-shell magnetic nanoparticles generating heat

under an electromagnetic field and killing cancer cells by hyperthermia
 

The practical utility of magnetic materials was identified thousands of years ago when lodestones were first used in compasses to navigate the oceans.

Today, magnetism forms the basis for many of the technologies we take for granted, as well as some with decidedly futuristic applications.

Jinwoo Cheon and colleagues from Yonsei University, the Korea Basic Science Institution and the Yonsei University College of Medicine in Korea have now worked out how to maximize the heat produced by magnetic nanoparticles to extraordinary effect in the treatment of cancer.¹

When magnetic particles are exposed to electromagnetic waves, magnetic spin relaxation processes lead to the production of heat which, if great enough, can kill cancer cells. Hyperthermia as it is known can also be generated in nonmagnetic nanoparticles, but the advantage of the magnetic approach is that the method can be used much deeper in the body. The challenge of magnetically induced hyperthermia is how to generate enough heat.

Cheon’s team used a theoretical model to probe the effect of nanoparticle diameter, composition and magnetization on magnetic heating power.

Doing so, they found optimal ranges for heat generation.

To obtain nanoparticles with properties that allowed them to respond in these ranges, the researchers fabricated core-shell composite nanoparticles containing mutually coupled ‘soft’ and ‘hard’ magnetic components. The resultant nanoparticles had a cobalt-iron oxide core and a manganese-iron oxide shell.

The utility of the nanoparticles in attacking human cancer cells was tested by injecting a suspension of the nanoparticles into tumors xenografted onto mice.

The mice were placed in a water-cooled magnetic induction coil and exposed to an electromagnetic field for 10 minutes. In contrast to the control mice, which experienced a multifold increase in tumor size over the next three weeks, the tumors on the mice treated with the nanoparticles had completely disappeared.

Only 75 μg of nanoparticles were required for complete elimination of the tumor.

"In the continuation of our research, we intend to explore other nanoparticle candidates with enhanced heat generation capabilities. We will also test the therapeutic efficacy of the approach in other tumor models as well as in vivo toxicity assessment and mass production of the nanoparticles," says Cheon.
 

Reference

Lee, J.-H.1, Jang, J.-T.1, Choi, J.-S.1, Moon, S. H.1, Noh, S.-H.1, Kim, J.-W.1, Kim, J.-G.2, Kim, I.-S.3, Park, K. I.3, Cheon, J.1 Exchange-coupled magnetic nanoparticles for efficient heat induction. Nature Nanotechnol. 6, 418–422 (2011). | article
 

Author affiliation

1. Department of Chemistry, Yonsei University, Seoul 120-749, Korea
2. Division of Electron Microscopic Research, Korea Basic Science Institution, Daejeon 305-333, Korea
3. Department of Pediatrics and BK21, Yonsei University College of Medicine, Seoul 120-752, Korea