Nanocomposite can be used to destroy cancerous tumours

Ian Baker of Dartmouth College in New Hampshire and colleagues have found that iron particles have a large "specific absorption rate" and so produce lots of heat. The iron particles are then coated with iron oxide, which allows the nanoparticles to be observed using magnetic resonance imaging (MRI).

Scientists have known for 50 years that magnetic nanoparticles can heat up in an alternating magnetic field. However, the nanoparticles need to have a high specific absorption rate (SAR) if they are to be used for destroying tumours. A large SAR not only reduces the dose of nanoparticles required but also minimizes the region treated, so that the heat from the nanoparticles does not affect surrounding healthy tissue.

Iron oxide particles have been used to induce hyperthermia because of their excellent biocompatibility and their good SAR, which results in efficient heating. For clinical applications, scientists also need to be able to observe the nanoparticles in vivo before starting treatment. Superparamagnetic iron nanoparticles typically 4?nm across are used for imaging using MRI but the problem is that these particles are not very efficient for magnetic heating.

Baker and co-workers may now have overcome this dilemma – by using iron particles coated with iron oxide nanoparticles. The saturation magnetisation of iron is more than twice that of an iron oxide particle so the SAR also doubles. But, since pure iron cannot be imaged using MRI, the researchers decided to coat it with a thin shell of iron oxide nanoparticles. They therefore have the best of both worlds: the high SAR of iron for heating and the iron oxide film for imaging.

The iron oxide coating also passivates the core iron particles, which are unstable and would otherwise oxidise.

The nanocomposite particles could be used to treat cancer in two ways. The first is to antibody-tag the nanoparticles and inject them into the bloodstream, where they will then find their way to the tumour. The second, which is more suitable for near-surface tumours (like neck tumours), is to directly inject the nanocomposites into the tumour.

Baker told nanotechweb.org that the production method is relatively simple and cheap, and that the nanoparticles produced are fairly uniform in size.

The team now plans to vary the particle size and work on developing different coatings for the particles. Next, the researchers hope to perform in vivo studies by directly injecting the nanoparticles into mice with tumours, as they have already done with iron oxide particles.