Nitroxide spin labels as NMR contrast agents: Delivery, metabolism and relaxation

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7254213

Chan, H C

The potential of nitroxides as contrast agents for magnetic resonance imaging (MRI) has been studied. The difficulties involved in using nitroxides as in vivo MRI contrast agents, such as premature metabolic convertion of nitroxides to their nonparamagnetic state, lack of tissue selectivity, and relatively low relaxivity of nitroxides, were, in part, overcome by the use of liposomes as the delivery system. A positively charged aqueous nitroxide, 2,2,6,6-tetramethyl-piperidine-N-oxyl-4-trimethylammonium (Cat1), which does not cross the cell membrane readily, was encapsulated in liposomes. The metabolic reduction of liposome-delivered Cat1 by cells was studied as a function of oxygen concentration, and the rate was found to be increased under hypoxic conditions. Liposomes with different phospholipid compositions were constructed. The physical states, fluid or solid, of these liposomal membranes were found to determine the mechanism by which the liposomes interact with cells.

• Research Organization: Illinois Univ., Urbana, IL (USA)
• OSTI ID: 7254213
• Country of Publication: United States
• Language: English

Related Subjects

550600 -- Medicine
560300* -- Chemicals Metabolism & Toxicology
62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANOXIA
CELL CONSTITUENTS
CELL MEMBRANES
CHALCOGENIDES
CHEMICAL COMPOSITION
DIAGNOSTIC TECHNIQUES
LIPOSOMES
MEMBRANES
METABOLISM
NITROGEN COMPOUNDS
NITROGEN OXIDES
NMR IMAGING
ORGANOIDS
OXIDES
OXYGEN COMPOUNDS