Cationic vesicles from novel bolaamphiphilic compounds

Abstract

Effective targeted drug delivery by cationic liposomes is difficult to achieve because of their rapid clearance from the blood circulation. Bolaamphiphiles that form monolayer membrane may provide vesicles with improved stability, as shown for archaeosomes. We investigated a series of bolaamphiphiles with acetylcholine head groups and systematic structural changes in their hydrophobic domain for their ability to form stable nanovesicles. Bolaamphiphiles with two aliphatic chains separated by a short amide midsection produced spherical nanovesicles ranging in diameter from 80 to 120 nm. These vesicles lost their encapsulated material within 24 hours of incubation in phosphate-buffered saline (PBS). Similar bolaamphiphiles with a longer midsection produced a mixture of fibers and more stable nanovesicles. Bolaamphiphiles with ester amide midsection produced only spherical nanovesicles that were stable during incubation in PBS for several days. Vesicles made from bolaamphiphiles with acetylcholine head groups conjugated to the aliphatic chain via the amine were less stable than vesicles made from bolaamphiphiles with head groups conjugated to the aliphatic chain via the acetyl group. Vesicles that were stable in vitro showed good stability in the blood circulation after intravenous administration to mice. These results help in elucidating the bolaamphiphile structures needed to form stable cationic vesicles for targeted drug delivery.