Ufasomes: A Vesicular Drug Delivery

Unsaturated fatty acid vesicles (ufasomes) are suspensions of closed lipid bilayers that are composed of fatty acids, and their ionized species (soap) which are restricted to narrow pH range from 7 to 9. In ufasomes, fatty acid molecules are oriented in such a way that their hydrocarbon tails are directed toward the membrane interior and the carboxyl groups are in contact with water. Stable ufasome formulation critically depends on proper selection of fatty acid, amount of cholesterol, buffer, pH range, amount of lipoxygenase, and the presence of divalent cations. Recent innovations can provide opportunity to formulate ufasomes with tailorable features such as extension of pH range, insensitivity toward divalent cations, and enhancement of stability. This article describes method of ufasome preparation, key issues in ufasome manufacturing, recent innovations in ufasomes, dynamicity, stability, and microscopic characterization of ufasomes. Later part of this article deals with comparison of ufasomes with thoroughly studied liposomes. However, even natural phospholipids are chemically heterogeneous, and pure synthetic phospholipids are not yet available in reasonable quantities. The advantage of ufasomes over liposomes is the ready availability of fatty acids.[3,4] Method of preparation Only unoxidized materials are preferred for preparation of ufasome. Stock solutions containing 10% of oleic and linoleic acids in chloroform are prepared and stored at 20°C. For typical preparations, 0.02 ml of the stock solution is evaporated in a test tube on a water pump and finally dried with a stream of nitrogen. The fatty acid film is then broken up completely in 0.2 ml of 0.1 M tris-hydroxymethyl aminomethane buffer, pH 8–9, by vigorous shaking on a vortex mixer. The resultant suspensions of ufasomes are stable for at least 24 h. In some experiments, an ultrasonic generator with a titanium microtip is used to prepare the particles. Air is first removed from the buffer by a stream of nitrogen and the suspension is blanketed with the gas during irradiation. Constant temperature is maintained by an ice water bath.[3] Key issues in manufacturing of ufasomes Selection of fatty acid Analysis of natural membrane phospholipids and information from the pressure area measurements on fatty acid surface films suggest that the 12 to 22 carbon fatty acids would be suitable for formulation of stable ufasomes. In fact, most of the studies were confined to the C-18 acids because they showed the greatest promise in early trials. Only oleic acid (cis-9-octadecenoic acid) and linoleic acid (cis, cis-9,12-octadecadienoic acid) formed membranes that enabled the ufasomes to fulfill these criteria. Of other fatty acids, palmitic Access this article online Website: www.sysrevpharm.org Quick Response Code: DOI: 10.4103/0975-8453.86290