Non-invasive evaluation of the location, the functional integrity and the oxygen supply of implants: 19F nuclear magnetic resonance imaging of perfluorocarbon-loaded Ba2+-alginate beads.
19F nuclear magnetic resonance imaging (MRI) can be used as a non-invasive tool to simultaneously determine the location, the integrity and the oxygen supply of Ba2+-alginate implants. This requires that the beads (implants) are pre-loaded with the perfluorocarbon compound F-44E. Implantation of solid 19F-labelled beads into the peritoneum, below the kidney capsule or into the muscle of Wistar WU rats demonstrated that these beads could be detected by 19F-MRI for up to 18 months after implantation. This indicated that F-44E is not considerably released from the beads during implantation. The signal to noise ratio of liquid-core beads was higher by a factor of 4 than the signal to noise ratio of solid beads, but liquid-core beads were more fragile and also too large for implantation under the kidney capsule and into the intramuscular tissue. Quantitative 2-dimensional 19F-T1 maps (resolution 0.5 x 0.5 mm) could be deduced from 19F-MRI measurements. These T1-maps correlated to the local pO2-values. The partial oxygen pressure estimated in F-44E-loaded Ba2+-alginate beads showed that the oxygen supply inside the beads was very poor when they were implanted below the kidney capsule or into the peritoneal cavity. These low pO2-values obtained for the renal subcapsular site and the peritoneum may explain the failure of previous immunoisolated islet transplantation studies using these locations.
Zimmermann
U
U
Lehrstuhl für Biotechnologie, Biozentrum, Am Hubland, Würzburg, Germany.
Nöth
U
U
Gröhn
P
P
Jork
A
A
Ulrichs
K
K
Lutz
J
J
Haase
A
A
D000464:Alginates / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D001464:Barium / Q000378:metabolism; D001672:Biocompatible Materials; D001785:Blood Gas Monitoring, Transcutaneous / Q000379:methods*; D002214:Capsules; D004355:Drug Stability; D005069:Evaluation Studies as Topic; D005260:Female; D005461:Fluorine; D005466:Fluorocarbons / Q000378:metabolism / Q000633:toxicity; D020007:Implants, Experimental; D007668:Kidney; D007739:L Cells; D008279:Magnetic Resonance Imaging; D051379:Mice; D018482:Muscle, Skeletal; D010529:Peritoneal Cavity; D051381:Rats; D017208:Rats, Wistar; D012680:Sensitivity and Specificity; D013997:Time Factors
D000464:Alginates; D001672:Biocompatible Materials; D002214:Capsules; D005466:Fluorocarbons; D001464:Barium; D005461:Fluorine; C057576:bis(perfluorobutyl)ethene