Imaging islets labeled with magnetic nanoparticles at 1.5 Tesla.
We have developed a magnetic resonance imaging (MRI) technique for imaging Feridex (superparamagnetic iron oxide [SPIO])-labeled islets of Langerhans using a standard clinical 1.5-Tesla (T) scanner and employing steady-state acquisition imaging sequence (3DFIESTA). Both porcine and rat islets were labeled with SPIO by a transfection technique using a combination of poly-l-lysine and electroporation. Electron microscopy demonstrated presence of SPIO particles within the individual islet cells, including beta-cells and particles trapped between cell membranes. Our labeling method produced a transfection rate of 860 pg to 3.4 ng iron per islet, dependent on the size of the islet. The labeling procedure did not disrupt either the function or viability of the islets. In vitro 3DFIESTA magnetic resonance images of single-labeled islets corresponded with their optical images. In vivo T2*-weighted scan using 1.5 T detected as few as 200 SPIO-labeled islets transplanted under rat kidney capsule, which correlated with immunohistochemistry of the transplant for insulin and iron. Ex vivo 3DFIESTA images of kidneys containing 200, 800 or 2,000 SPIO-labeled islet isografts showed good correlation between signal loss and increasing numbers of islets. These data provide evidence that islets can be labeled with SPIO and imaged using clinically available 1.5- T MRI.
Tai
Joo Ho
JH
FRCPath, Novartis/Stiller Professor of Xenotransplantation, Robarts Research Institute, Room 200, SDRI Building, University of Western Ontario, 1400 Western Rd., London, Ontario, Canada.
Foster
Paula
P
Rosales
Alma
A
Feng
Biao
B
Hasilo
Craig
C
Martinez
Violetta
V
Ramadan
Soha
S
Snir
Jonatan
J
Melling
C W James
CW
Dhanvantari
Savita
S
Rutt
Brian
B
White
David J G
DJ
D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival; D018274:Electroporation; D007505:Iron-Dextran Complex; D007515:Islets of Langerhans / Q000166:cytology* / Q000648:ultrastructure; D016381:Islets of Langerhans Transplantation / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D023421:Models, Animal; D051381:Rats; D011917:Rats, Inbred Lew; D012680:Sensitivity and Specificity; D013370:Subrenal Capsule Assay; D013552:Swine; D014182:Transplantation, Autologous
D007505:Iron-Dextran Complex