Stem cell tracker: MRI nano tags

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  • Published: Jul 1, 2012
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Stem cell tracker: MRI nano tags

Tracking device

Lara Bogart uses a photothermal microscope to examine live stem cells. (Credit: Image courtesy of University of Liverpool)
Lara Bogart, University of Liverpool

It is now possible to track stem cells using magnetic resonance imaging by tagging them with superparamagnetic iron oxide nanoparticles (SPIONs). The tags could enable researchers and medics to follow the path taken by therapeutic stem cells and to ensure that they reach their target site. Researchers at the University of Liverpool in the UK realised that in order for the technology to be developed further - and to increase the timescale on which stem cells might be tracked - more information is needed regarding the structure of such tags and how they interact with stem cells.

Stem cells have emerged as a fascinating area of therapeutics and have been used with some success to treat conditions such as leukaemia. They have the potential to be used in addressing the problem of many more diseases and disorders where patient survival is otherwise dependent on the donation of human organs or other tissues. Unfortunately, it is hard to determine whether or not stem cells survive transplantation from source to the patient's body and whether or not the cells reach their therapeutic target site or migrate elsewhere.

The Liverpool team has turned to photothermal microscopy to study how SPIONs interact with stem cells. They explain that SPIONs can be used to "label" stem cells prior to being administered to the patient, which then improve contrast in magnetic resonance imaging. Current approaches allow SPIONs to be used only for short-timescale studies as the particles degrade fairly rapidly under physiological conditions; timescales which are shorter than those at which adverse effects may occur. Advances in the lifetime of such contrast agents can only be gained by improvements in our knowledge of how these tags interact with cells. However, progress in understanding the cellular fate of SPIONs is currently limited by the lack of techniques suitable for both imaging and magnetic characterisation in live cells.

Lara Bogart in the University's Institute of Integrative Biology and colleagues, Arthur Taylor, Yann Cesbron, Patricia Murray, and Raphaël Lévy, have found a way to directly image the iron oxide core of the SPIONs."This offers two important advantages when compared with current strategies employed to image magnetic cores," the team says, "first, it is non-destructive and is therefore suitable for studies of live cells and, second, it offers a higher sensitivity and resolution, thus allowing for the identification of low levels of SPIONs within a precise subcellular location." This approach side-steps the issue of fluorescent tags, and so can be used to study clinically approved SPIONs.

Targeting disease

"Stem cells have the potential to replace and repair damaged tissue to preclude the need for a patient to wait for an organ or tissue transplant," Bogart explains. "Research is ongoing into how it could be used to treat a wide variety of diseases such as Alzheimer's, Parkinson's disease, and Type I diabetes."In order to fully explore this potential, however, more technological developments are needed to understand how stem cells behave in the body after transplantation. If we cannot monitor stem cells effectively, it could have serious implications for patient health. Studies have already shown that if cells migrate to the circulatory system, beyond their target organ or tissue site, then it can cause inflammation in the body."

The team further explains that their technique can produce images of mock histological slices. "We have been able to identify cells labelled with SPIONs from a mixed population containing predominantly unlabelled cells," the team says. "The identification of SPION-labelled cells within large populations of cells will provide information on the long-term fate of SPIONs, and will enable us to determine if SPION-labelled cells have migrated to organs other than their intended site," Bogart says.

Related Links

ACS Nano, 2012; 120607110419005: "Photothermal Microscopy of the Core of Dextran-Coated Iron Oxide Nanoparticles During Cell Uptake"

Article by David Bradley

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

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