MRI monitors anticancer nanotubes

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  • Published: Aug 1, 2010
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: MRI monitors anticancer nanotubes

Magnetic resonance imaging can now be used to monitor carbon nanotubes aimed at destroying tumour cells by near-infra-red laser induced heating, according to US researchers.

An experimental technique for destroying tumours, known as laser-induced thermal therapy (LITT), uses nanoparticles to absorb energy from a laser and so heat and destroy cancerous tissue. However, while a tumour may be clearly visible in a medical scan, the nanoparticles, multiwalled carbon nanotubes, are not. The nanotubes cannot be tracked once injected into a patient, which means that if they have not homed in on the tumour they could cause laser heating of healthy tissue.

The research is part of Xuanfeng "Leo" Ding's ongoing Ph.D. work at Wake Forest University Baptist Medical Center in North Carolina, USA, which is a multi-disciplinary project supervised by Suzy Torti, professor of biochemistry at Wake Forest Baptist, and David Carroll, director of the Wake Forest University Center for Nanotechnology and Molecular Materials. In a previous component of the work, the same group demonstrated how laser-induced thermal therapy with another nanoparticle system increased the long-term survival of mice with tumours. The team demonstrated that use of MWCNTs enabled ablation of renal tumours in mice with a low laser power of just 3 Watts per square centimetre and very short single treatment time of only 30 seconds. The therapy had minimal local toxicity and no evident systemic toxicity, the team reported previously. (PNAS, 2009, 106, 12897-12902; http://dx.doi.org/10.1073/pnas.0905195106)

Now, Ding, Torti, Carroll, and their colleagues, have shown for the first time that it is possible to make the particles visible in MRI by loading them up with iron particle so that tumour imaging and laser ablation can be carried out at the same time. The team has demonstrated proof of principle using experimental tissue containing mouse tumours. They reported more details of the technique at the 52nd Annual Meeting of the American Association of Physicists in Medicine (AAPM) in Philadelphia, Pennsylvania, in July.

"To find the exact location of the nanoparticle in the human body is very important to the treatment," explains Ding. "It is really exciting to watch the tumour labelled with the nanotubes begin to shrink after the treatment."

"MWCNT R2 (or 1/T2) measurements, shows that the R2 of the 600mg Fe MWCNT is about five times higher than R2 for a commercial MR contrast agent (Feridex I.V. (ferumoxides))," the researchers reported, " Furthermore, the in vivo MR study shows that 600mg Fe MWCNTs effectively change the tumour T2 relaxation from 61 to 22 ms and create a void signal in the implanted target area, enabling tumour localization for MR-guided LITT."

The researchers tested the MRI relaxation properties of three different iron-containing MWCNT solutions (containing 600, 200, and 60 milligrams of ferrocene during manufacture as the source of iron) using a 1.5T MRI scanner with a multi-echo pulse sequence. Experimental mice with breast tumours were then injected with 600mg Fe MWCNTs and N-Doped MWCNTs (almost iron free) directly into their tumours.

The next step in this project is to see if the iron-loaded nanoparticles can do the same thing. "Iron-containing MWCNTs have favourable magnetic resonance relaxation values and biological stability, and show great potential as a dual-modality agent for T2 MR contrast imaging and NIR laser absorption for MR-guided LITT," the team reported to the AAPM meeting. If successful at the next stage, there would then be several years of clinical trials before the approach would be made available to oncologists and their patients.

 



The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

 

 

Credit: Xuanfeng Ding

Laser ablation improved by iron-loaded anticancer nanotubes

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