Tracking stem cells: Nanoparticle tags for MRI

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  • Published: Mar 1, 2011
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Tracking stem cells: Nanoparticle tags for MRI

Magnetic cell tracker

Stem cells labelled with hollow biocompatible cobalt-platinum (CoPt) nanoparticles remain stable for months and have a strong tendency to align with a magnetic field. The discovery allows low concentrations of the particles to be detected using magnetic resonance imaging (MRI) and so might provide medical researchers with the means to locate and track stem cells in the body.

Stem cells might be described as primordial cells, they can divide without limit and have the potential to differentiate into the different cell types from which livers, hearts, bones, brains and nerves, skin, blood cells and other organs are constructed. Scientists have suggested that harnessing the power of stem cells for repairing damaged or otherwise compromised tissues will open up new therapies for a wide range of problems. Among one of the most promising area is the use of neural stem cells in treating spinal cord injury.

Neural stem cells were first cultured in the laboratory in 1992 and by 2005, researchers at the University of California Irvine's Reeve-Irvine Research Center had partially restored the ability to walk in paralyzed mice using transplanted human neural stem cells. More recently, neural stem cells have entered ongoing Phase I human clinical trials for treating, not spinal injury, but patients with another debilitating problem, ALS (amyotrophic lateral sclerosis, or Lou Gehrig's disease).

However, research into the use of neural stem cells is somewhat hindered by difficulties facing researchers in tracking and monitoring the movements of the cells once they have been injected. This would be a particularly tough obstacle to overcome in treating spinally injured people and might stymie development. Fortunately, the advent of nanotechnology could help remedy this situation.

Nguyen Thanh of The Davy-Faraday Research Laboratory, at The Royal Institution of Great Britain and University College London, Xiaoting Meng and Bing Song of Cardiff Institute of Tissue Engineering & Repair, Cardiff University, Hugh Seton of the School of Medical Sciences, University of Aberdeen, chemist Le Lu of the University of Liverpool and Ian Prior in the Physiological Laboratory at Liverpool, have now developed hollow biocompatible cobalt-platinum nanoparticles which they were able to attach to stem cells. The nanoparticles have a high magnetic moment, which means they can be detected using magnetic resonance imaging (MRI) even at low concentrations. Crucially, the particles are also stable for weeks and so might be used to track stem cells during the critical early stages treatment.

Conjugated insights

So far, the team has carried out in vitro tracking using slices of spinal cord into which the stem cell nanoparticle conjugates were injected. Initial MRI results on these spinal cord slices suggest that the particles were still trackable even two weeks after injection. The researchers point out that the presence of the nanoparticle partner did not seem to affect stem cell viability. The CoPt hollow nanoparticles are from pH 1.5 to 10 and at up to 2 molar saline for many months; earlier attempts at developing such particles suffered from low stability.

"The new method demonstrates the feasibility of reliable, non-invasive MRI imaging of nanoparticle-labelled cells," says Thanh. "This also potentially opens up many doors to optimise stem cell response post transplantation in treating other diseases," adds Song. Neurotransplantation of stem cells holds much promise for treating with acute and chronic diseases of the central nervous system of which there are many. Non-invasive cellular imaging will facilitate greatly the development of novel treatments especially given the high spatial resolution of MRI and its "in vivo modality". This approach to stem cell conjugate nanoparticles might also find utility in treatment of spinal cord injury as well as in the diagnosis and treatment of neurological diseases.

 



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

  Hollow biocompatible cobalt-platinum (CoPt) nanoparticles attached to stem cells remain stable for months and have a strong tendency to align with a magnetic field. The discovery allows low concentrations of the particles to be detected using magnetic resonance imaging (MRI) and so might provide medical researchers with the means to locate and track stem cells in the body.
CoPt-labelled stem cells by MRI
Credit: Thanh et al, Nanoscale

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