Quantitative MR imaging of targeted SPIO particles on the cell surface and comparison to flow cytometry.
OBJECTIVE
To detect anti-CEACAM5 targeted superparamagnetic iron oxide (SPIO) particles in vitro on the cell surface by quantitative magnetic resonance (MR) imaging and to compare with flow cytometry.


METHODS
The monoclonal mouse antibody T84.1 and an appropriate IgG isotype antibody were conjugated to dextran-coated SPIO particles. HT29 cells expressing carcinoembryonic antigen (CEACAM5) were treated with antibody-conjugated SPIO particles. Purified cell samples were examined on a 3.0-T MR scanner using a multi-echo spin-echo sequence for MR relaxometry. Aliquots of the cell samples were further treated with a fluorescein isothiocyanate (FITC) anti-dextran antibody and an Alexa Fluor 488 anti-mouse antibody for the corresponding flow cytometry.


RESULTS
MR relaxometry revealed a dose-dependent binding of T84.1-conjugated SPIO particles with a positive correlation between R(2) relaxation rate of cell samples and SPIO particle concentration during incubation (r=0.993, P<.01). Positive correlations were also observed between R(2) relaxation rate and flow cytometry (geometric mean) with both fluorescent antibodies (r=0.972 and r=0.953, both P<.01), respectively.


CONCLUSIONS
The study revealed the feasibility of quantitative MR imaging of targeted SPIO particles on the cell surface comparable to flow cytometry.
Peldschus
Kersten
K
Department of Diagnostic and Interventional Radiology, University Cancer Center Hamburg-Eppendorf, 20246 Hamburg, Germany. k.peldschus@uke.uni-hamburg.de
Schultze
Alexander
A
Nollau
Peter
P
Kaul
Michael
M
Schumacher
Udo
U
Wagener
Christoph
C
Adam
Gerhard
G
Ittrich
Harald
H
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002272:Carcinoembryonic Antigen / Q000737:chemistry; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism / Q000473:pathology*; D003287:Contrast Media / Q000494:pharmacology*; D052203:Ferrosoferric Oxide / Q000494:pharmacology*; D005434:Flow Cytometry / Q000379:methods*; D016650:Fluorescein-5-isothiocyanate / Q000494:pharmacology; D058851:GPI-Linked Proteins; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice
C417561:Alexa 488 hydrazide; D000911:Antibodies, Monoclonal; C527875:CEACAM5 protein, human; D002272:Carcinoembryonic Antigen; D003287:Contrast Media; D058851:GPI-Linked Proteins; D006834:Hydrazines; D016650:Fluorescein-5-isothiocyanate; D052203:Ferrosoferric Oxide