E Unger1, T Fritz, D K Shen, G Wu. 1. Department of Radiology, University of Arizona Health Sciences Center, Tucson, AZ 85724.
Abstract
RATIONALE AND OBJECTIVES: The purpose of this study was to further develop and compare manganese-based liposomes prepared by two different approaches wherein a manganese ion was entrapped within the internal aqueous space of the vesicles or into the bilayer surface via membrane bound complexes. METHODS: Small unilamellar liposomes (SUVs) were prepared entrapping manganese chloride. Alkylated complexes of manganese were prepared and also incorporated into SUVs. The two different manganese-based liposomes were compared for in-vitro relaxivity, stability, toxicity, and in-vivo imaging in rats with liver tumors. RESULTS: Liposomes entrapping manganese had a concentration-dependent change in relaxivity that was maximal at a several-fold molar excess of phospholipid relative to manganese ion. Liposomes bearing membrane-bound complexes showed relaxivity inversely proportional to vesicle size. In-vivo imaging showed greater and more specific hepatic enhancement with manganese liposomes bearing alkylated complexes than those entrapping manganese ion. CONCLUSIONS: Correlation effects likely explain the increased relaxivity of manganese entrapped in phospholipid vesicles. Greater efficacy, however, is afforded by liposomes bearing alkylated complexes.
RATIONALE AND OBJECTIVES: The purpose of this study was to further develop and compare manganese-based liposomes prepared by two different approaches wherein a manganese ion was entrapped within the internal aqueous space of the vesicles or into the bilayer surface via membrane bound complexes. METHODS: Small unilamellar liposomes (SUVs) were prepared entrapping manganese chloride. Alkylated complexes of manganese were prepared and also incorporated into SUVs. The two different manganese-based liposomes were compared for in-vitro relaxivity, stability, toxicity, and in-vivo imaging in rats with liver tumors. RESULTS: Liposomes entrapping manganese had a concentration-dependent change in relaxivity that was maximal at a several-fold molar excess of phospholipid relative to manganese ion. Liposomes bearing membrane-bound complexes showed relaxivity inversely proportional to vesicle size. In-vivo imaging showed greater and more specific hepatic enhancement with manganese liposomes bearing alkylated complexes than those entrapping manganese ion. CONCLUSIONS: Correlation effects likely explain the increased relaxivity of manganese entrapped in phospholipid vesicles. Greater efficacy, however, is afforded by liposomes bearing alkylated complexes.
Authors: Dipanjan Pan; Shelton D Caruthers; Angana Senpan; Ann H Schmieder; Samuel A Wickline; Gregory M Lanza Journal: Wiley Interdiscip Rev Nanomed Nanobiotechnol Date: 2010-09-21