Mark Christopher Spoerl, Presenter: Nothing to Disclose

Konstanze Aurich PhD, Abstract Co-Author: Nothing to Disclose

Birgitt Fürll, Abstract Co-Author: Nothing to Disclose

Andreas Greinacher MD, PhD, Abstract Co-Author: Nothing to Disclose

Werner Weitschies PhD, Abstract Co-Author: Nothing to Disclose

Norbert Hosten MD, Abstract Co-Author: Nothing to Disclose

Different cells have been successfully labelled for MR Imaging. We evaluated, whether human platelets could be labeled with iron oxide nanoparticles. Studies of cells in moving blood would be the ultimate aim of this technique.

At first, a suitable particle size and MRI settings were ascertained. MRI measurements were realized at a 7 Tesla Small animal device in different media. After labeling human platelets with Resovist® (Bayer Schering Pharma AG, Germany) by phagocytosis the particle location within cells was determined by transmission electron microscopy and confocal laser scanning microscopy (CLSM). Iron content per cell was determined by atomic absorption spectroscopy (AAS). To avoid an unrequested immune response, particles at the exterior cell membrane were eliminated by enzymatic digestion, which was demonstrated also by CLSM. Furthermore, blood flow conditions for MRI measurements were simulated.

Data describing signals from largest particles (95 nm) exhibit highest contrasts. Incubation time of 30 min and an iron concentration of 10 mM resulted in adequate cell labelling as determined by flow cytometry and AAS. MRI measurements of labeled cells resulted in considerably distinguishable images. Enzymatic degradation of carboxydextran shell of particles located at the exterior cell membrane resulted in loss of these particles as demonstrated by CLSM. Finally, labeled platelets are also visible in MRI under blood flow conditions.

Platelets can be labeled with superparamagnetic nanoparticles only by phagocytosis for detection in MRI allowing accurate tracking of their biodistribution following retransfusion. Labeled platelets offer sufficient iron concentration for being detected in MRI. Particles located at the exterior cell membrane could successfully be removed by enzymatic degradation of particle shell. A flow model is currently employed for determining the influences of blood flow on labeled platelets in MRI. Finally, positive results from cell tests and flow model will be transferred into animal models for MR imaging.

There are many platelet affecting diseases, where MRI tracking could provide information about homing and fate of these cells.

Spoerl, M, Aurich, K, Fürll, B, Greinacher, A, Weitschies, W, Hosten, N, Magnetically Labeled Platelets for Magnetic Resonance Tracking.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8004617.html