Controlled delivery of Gd-containing liposomes to lymph nodes: surface modification may enhance MRI contrast properties.
Surface modification of liposomes containing Gd-diethylenetriaminepentaacetyl-phosphatidylethanolamine (Gd-DTPA-PE) as an amphiphilic paramagnetic label influences their contrast properties as MRI agents. Liposomes with the mean diameter ca. 220 nm and 10% mol content of Gd-DTPA-PE were modified with dextran (molecular weight 6 kDa) or polyethyleneglycol (PEG, molecular weight 5 kDa). The preparations obtained were used for MR visualization of axillary and subscapular lymph nodes after SC injection into rabbit's paw. Dextran-modified liposomes were found to have limited or no effect on lymph node/muscle MR signal intensity ratio during the first 2 h after the administration when compared to nonmodified plain liposomes, whereas the liposomes modified with PEG demonstrated a 3-3.5-fold enhancement of lymph node signal. However, the partial biodistribution studies with the 111In-labeled liposomes revealed that PEG-modified vesicles accumulated in the axillary lymph node at half the amount comparing with nonmodified and dextran-modified liposomes. The phenomenon found might be explained by noticeably increased relaxivity of PEG-modified Gd-liposomes.
Trubetskoy
V S
VS
Center for Imaging and Pharmaceutical Research, Massachusetts General Hospital East, Charlestown 02129.
Cannillo
J A
JA
Milshtein
A
A
Wolf
G L
GL
Torchilin
V P
VP
D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage*; D003911:Dextrans; D019786:Gadolinium DTPA; D008081:Liposomes; D008198:Lymph Nodes / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D004369:Pentetic Acid / Q000031:analogs & derivatives*; D010714:Phosphatidylethanolamines; D011092:Polyethylene Glycols; D011817:Rabbits; D013499:Surface Properties
D003287:Contrast Media; D003911:Dextrans; D008081:Liposomes; D010714:Phosphatidylethanolamines; C082531:gadolinium phosphatidylethanolamine-DTPA; D011092:Polyethylene Glycols; D004369:Pentetic Acid; D019786:Gadolinium DTPA