British scientists have designed functionalized nanotubes that can act as both a contrast agent for Magnetic Resonance Imaging (MRI) and as a structure for targeted cancer treatment.

Carbon nanotubes (CNTs) have shown the potential for use in a range of biomedical applications, thanks to their outstanding mechanical, optical, and electronic properties. Magnetic functionalization of the CNTs confers additional properties which has seen their application as magnetic carriers in drug delivery and in a range of other magnetic therapies. But research from a team at Queen Mary, University of London, has shown that a single type of functionalized nanotube could find dual use, in both imaging and in cancer therapy.

There are two ways to functionalize CNTs – the central capillary of CNTs can be filled with magnetic nanostructures, or ions can be attached to the surface of the tube’s inert sidewalls. In order to provide dual functionalization, QMUL’s team, led by Mark Baxendale, did both. Using a simple wet chemical method, they filled the capillary of multiwalled CNTs with iron nanoparticles (a heating element), and functionalized the sidewalls with gadolinium (Gd) ions (which is paramagnetic).

Magnetic hyperthermia is a cancer treatment that involves injecting paramagnetic nanoparticles directly into a tumor, and applying an alternating magnetic field to produce an intense blast of heat that destroys the tumor. In the paper, which appears in the March issue of Carbon [DOI: 10.1016/j.carbon.2015.01.052], Baxendale demonstrated that their Gd-doped CNTs fulfilled the clinical requirements for hyperthermia treatment – under a magnetic field with strength 8 kA/m and frequency 696 kHz, the specific absorption rate of a gram of iron was 50W.

Gadolinium is already widely used in magnetic resonance imaging (MRI), in order to improve the visibility of internal body structures in an image. The use of the Gd-doped CNTs as an MRI contrast agent was determined by observing the room temperature electron paramagnetic resonance of the CNT, which was found to be comparable to those commercial Gd-based contrast agents.

This work has demonstrated that these hybrid structures show promise as candidate materials for use in both MRI imaging and magnetic hyperthermia cancer therapy. The authors are hopeful that their material will make their way to clinical trials.

Carbon, Volume 87, March 2015, Pages 226–232 “Iron-filled multiwalled carbon nanotubes surface-functionalized with paramagnetic Gd (III): A candidate dual-functioning MRI contrast agent and magnetic hyperthermia structure” DOI: 10.1016/j.carbon.2015.01.052