Osmotically shrunken LIPOCEST agents: an innovative class of magnetic resonance imaging contrast media based on chemical exchange saturation transfer.
The peculiar properties of osmotically shrunken liposomes acting as magnetic resonance imaging-chemical exchange saturation transfer (MRI-CEST) contrast agents have been investigated. Attention has been primarily devoted to assessing the contribution arising from encapsulated and incorporated paramagnetic lanthanide(III)-based shift reagents in determining the chemical shift of the intraliposomal water protons, which is a relevant factor for generating the CEST contrast. It is demonstrated that a highly shifted resonance for the encapsulated water can be attained by increasing the percentage of the amphiphilic shift reagent incorporated in the liposome bilayer. It is also demonstrated that the shift contribution arising from the bulk magnetic susceptibility can be optimized through the modulation of the osmotic shrinkage. In terms of sensitivity, it is shown that the saturation transfer efficiency can be significantly improved by increasing the size of the vesicle, thus allowing a high number of exchangeable protons to be saturated. In addition, the role played by the intensity of the saturating radiofrequency field has also been highlighted.
Terreno
Enzo
E
Department of Chemistry IFM and Molecular Imaging Center, University of Torino, Via P. Giuria 7, 10125 Torino, Italy.
Delli Castelli
Daniela
D
Violante
Elisabetta
E
Sanders
Honorius M H F
HM
Sommerdijk
Nico A J M
NA
Aime
Silvio
S
D003287:Contrast Media / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D046529:Microscopy, Electron, Transmission; D009995:Osmosis; D010316:Particle Size; D011522:Protons; D013696:Temperature; D014867:Water / Q000737:chemistry
D003287:Contrast Media; D028581:Lanthanoid Series Elements; D008081:Liposomes; D011522:Protons; D014867:Water