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15-03-2011 | Oncology | Article

Remote-controlled microcarriers can deliver cancer drugs directly to tumors


Free abstract

MedWire News: Canadian research results show that doxorubicin can be successfully administered to specific areas of a rabbit's liver using doxorubicin-loaded magnetic microcarriers guided by a magnetic resonance imaging (MRI) system.

These findings highlight "the potential of magnetic resonance navigation (MRN) to improve drug targeting in deep tissues," write Sylvain Martel (École Polytechnique de Montréal, Québec) and colleagues in the journal Biomaterials.

The researchers explain that magnetic targeting was proposed 30 years ago as a means to increase the concentration of cytotoxic agents in tumors.

It involves applying an external magnetic field to capture drug-loaded magnetic carriers in a targeted site, but suffers from intrinsic limitations, such as the inability to target areas within deep tissues, mainly due to a strong decrease of the magnetic field magnitude away from the magnets.

Recently MRN - the endovascular steering of therapeutic magnetic microcarriers (TMMC) - has been proposed as a clinically viable alternative to reach deep tissues.

In the present study, Martel and team tested MRN in a rabbit model.

They used an upgraded MRI system to guide the TMMC - biodegradable microparticles loaded with iron-cobalt nanoparticles and doxorubicin - through the hepatic artery to the liver.

The TMMC displayed high saturation magnetization (Ms=72 emu per g), MRI tracking compatibility (strong contrast on T2*-weighted images), appropriate size for the blood vessel embolization (approximately 50 µm), and sustained release of doxorubicin over several days, the investigators note.

They report that the TMMC were successfully steered to the left liver bifurcation and were mainly localized to the left lobes, with the right lobe apparently free from TMMC.

However, steering efficiency was affected by several different parameters including flow velocity, TMMC release site in the artery, magnetic gradient, and TMMC properties.

Martel et al believe that this is the first study to show that steering can be achieved in the hepatic artery, located at a depth of 4 cm below the skin, with moderate blood flow with an MRI scanner.

They say it "represents a significant step toward the development of tumor-targeted therapies and better control over the side effects."

"Further work will aim to target a liver tumor to evaluate MRN therapeutic efficacy," the team concludes.

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Laura Dean