Magnetic Field Directs Nanoparticles Within a Nanoparticle to Tumors

To improve the tumor-specific delivery of drugs to tumors, a team of investigators has devised a system of nanoparticles-within-a-nanoparticle that can be directed to and concentrated at the site of tumor utilizing a magnetic field. Once at the tumor site, radiofrequency irradiation triggers drug release from the nanoparticles, dipping the tumors in the drug and markedly reducing the growth of the tumors.

Reporting their findings online November 1, 2010, in the journal Nano Letters, researchers from the University of California, San Diego (UCSD; USA), led by Dr. Sungho Jin, described the multiple steps it uses to create the multicomponent nanoparticles that contain both magnetic nanoparticles and the drug Camptothecin trapped within a silica shell. Trapped within the silica nanoparticle, the close proximity of the hundreds of magnetic iron oxide nanoparticles increases their responsiveness to a magnetic field applied from outside the body. More significantly, at moderate magnetic field strengths the nanoparticles not only gather near a tumor but also penetrate into the tumor mass.

Based on these early results, the investigators injected the nanoparticles into laboratory mice implanted with human breast tumors. After using a magnetic field to direct the nanoparticles to tumors during a two-hour period, the researchers subjected the animals to three eight-minute exposures to radiofrequency irradiation. The treated animals experienced a marked reduction in the size of their tumors and experienced no noticeable side effects.

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