Multilayered vesicles prepared by reverse-phase evaporation: liposome structure and optimum solute entrapment

Journal Article · Tue Jan 13 00:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00375a004· OSTI ID:6789475

Pidgeon, C; McNeely, S; Schmidt, T; Johnson, J E

Liposome structure and solute entrapment in multilayered vesicles (MLVs) prepared by reverse-phase evaporation (REV) were studied. MLV-REV vesicles prepared from ether/water emulsions have high entrapment. Entrapment depends on drug, drug concentration, lipid, lipid concentration, and the container used to prepare the vesicles. By use of 300 /sup +/L of aqueous phase and 100 mg of phosphatidylcholine (PC), vesicles prepared in a test tube 25 mm x 175 mm have higher entrapment than vesicles prepared in a 100-mL round-bottom or pear-shaped flask. By use of a test tube, 100 mg of PC, and 300 ..mu..L of aqueous phase containing sucrose (1-50 mg/mL), >90% sucrose entrapment was obtained. Increasing lipid content to 150 mg of PC decreased entrapment to approx.80%. Neutral PC MLV-REV vesicles have optimum entrapment. Mixing negatively charged lipids or cholesterol (CH) with PC to make MLV-REV vesicles results in decreased entrapment compared to using only PC. Preparing vesicles with the solid lipid dipalmitoylphosphatidylcholine (DPPC) or DPPC/CH mixtures results in 30-40% entrapment when diethyl ether is used to make the MLV-REV emulsion. The high entrapment found for MLV vesicles prepared from water/organic solvent emulsions depends on maintaining a core during the process of liposome formation. A method to calculate the fraction of water residing in the liposomes' core is presented and used to compare multilayered vesicles prepared by different processes. X-ray diffraction data demonstrate that a heterogeneous distribution of lipid may exist in multilayered vesicles prepared by the REV process.

• Research Organization: Lilly Research Lab., Indianapolis, IN
• OSTI ID: 6789475
• Journal Information: Biochemistry; (United States), Vol. 26:1
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
LIPOSOMES
MOLECULAR STRUCTURE
X-RAY DIFFRACTION
AQUEOUS SOLUTIONS
CHOLESTEROL
EVAPORATION
LIPIDS
PHOSPHOLIPIDS
SOLUTES
CELL CONSTITUENTS
COHERENT SCATTERING
DIFFRACTION
DISPERSIONS
ESTERS
HYDROXY COMPOUNDS
MIXTURES
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANOIDS
PHASE TRANSFORMATIONS
SCATTERING
SOLUTIONS
STEROIDS
STEROLS
550602* - Medicine- External Radiation in Diagnostics- (1980-)