Abstract:

The use of phospholipids (PL) as surfactants in micellar systems and microemulsions offers many advantages as drug delivery vehicles. PL are commonly used in combination with other non-food surfactants with cosolvents and cosurfactants to form a cascade of delivery structures. The authors incorporated phosphatidylcholine (PC) in a unique U-type water-dilutable phase diagrams exhibiting large isotropic regions of nanostructures. The nanometric liq. structures were prepd. from food-grade emulsifiers. The authors formed water-free concs. with PC that are fully dild. with water to form a variety of unusually structured nanodroplets. Due to the uniqueness of their compn., the designed concs. derived from the nature of the oil phase, type of surfactants, and cosurfactants were characterized and found to be direct micelles (rather than inverse micelles), with the surfactant headgroups convexed toward the hydrophilic phase away from the micelle's core, even in the absence of water. The concs. tend to self-assemble upon adding water to form O/W microemulsions even with small amts. of water (water-poor compns. of 0-20% water). Upon further diln. with water the swollen micelles retain the oil as the inner phase. Multi-component compns. with two types of hydrophilic surfactants were investigated. The most significant enhancement in the total isotropic region was obtained by decreasing the triacetin and PC content in the system. The authors explored, by varying the nature of the headgroups and the nature and length of the lipidic (lipophilic) tails of the PL, the diln. capabilities of each of the systems. [on SciFinder(R)]