Aug 12, 2009
Magnetic nanomaterials gear up for multimodal cancer therapy
Multimodal cancer therapy – simultaneous chemotherapy and hyperthermia (raising the tumor temperature to 41–48 °C) provides a synergistic effect and enhances the efficacy of cancer treatment compared with sequential application. Potent anti-cancer drugs exist, but with conventional delivery methods their power is not fully utilized. Due to systemic distribution, large doses are required, which can result in severe damage to healthy cells as well as insufficient drug concentration in the tumor. Existing hyperthermia techniques are hampered by invasiveness, poor temperature distribution and insufficient temperature rise in the tumor.
Composite nanoparticles consisting of a magnetic iron oxide core and a special thermoresponsive polymeric shell are promising materials for multimodal cancer therapy, negating many of the drawbacks of conventional therapies. Drug targeting is achieved by loading these tiny particles with potent anti-cancer drugs, injecting them into the bloodstream and using an external magnetic field gradient to accurately guide them to the tumor. This minimizes systemic distribution and toxicity, and ensures sufficient drug concentration in the tumor.
After the particles are localized in the tumor, an external alternating magnetic field is applied to generate heat in the magnetic nanoparticles. This heat raises the temperature of the surrounding polymer shell, resulting in thermoresponsive behaviour that causes the polymer to shrink and release the anti-cancer drug. Thus, simultaneous hyperthermia and chemotherapy can be achieved, thereby utilizing the synergistic effect. An on-off controlled drug release can also be achieved.
Particles with a purpose
Researchers at Nanyang Technological University, Singapore, and Singapore General Hospital have developed composite magnetic nanoparticles for this purpose. The particles consist of a magnetic core of iron oxide and a shell of the thermoresponsive polymer poly-n-isopropylacrylamide loaded with the anti-cancer drug doxorubicin.
In vivo magnetic targeting of drug-loaded nanoparticles to a liver tumor in a rat model was demonstrated and visualized by MRI. Histology confirmed the localization of the particles to the liver tumor with no occurrence in other organs. In vitro experiments showed that the particles simultaneously generate heat as well as release therapeutically relevant quantities of drugs when exposed to an alternating magnetic field, making them promising materials for multimodal cancer therapy.
The researchers presented their work in Nanotechnology.
About the author
The work was performed at the Nanyang Technological University (NTU) and the Singapore General Hospital (SGH), Singapore. S Purushotham is a graduate student, under the supervision of Prof. R V Ramanujan, at the School of Materials Science and Engineering, NTU. P E J Chang and C K Tan are oncologists at the Department of Gastroenterology and Hepatology, SGH. H Rumpel is at the Department of Diagnostic Radiology, SGH. I H C Kee and R T H Ng are at the Department of Experimental Surgery, SGH. P K H Chow is affiliated with the Department of Experimental Surgery, SGH.