Polyhedral non-ionic surfactant vesicles.
Large polyhedral (2-10 microns) non-ionic surfactant vesicles (niosomes) formed from mixtures of a hexadecyl diglycerol ether (C16G2), a cholesteryl poly-24-oxyethylene ether (solulan C24) and a low level of cholesterol are being investigated as slow-release systems for ophthalmic, subcutaneous or intramuscular administration. The phase-diagram of this three-component system has been constructed and these polyhedral vesicles are found to be in the gel (L beta) phase. Confocal laser-scanning microscopy was used to confirm the complex morphology of these vesicles. The thermo-responsive nature of release of entrapped carboxyfluorescein and nicotinamide adenine dinucleotide has been studied; release is increased with increase in temperature (37 degrees C) even though the polyhedral vesicles still maintain their polyhedral shape at this temperature. The results indicate that the thermo-responsive features of the niosomes are a result of reversible changes in bi-layer permeability caused by temperature-mediated alteration in the membrane-packing characteristics of the polyethoxylated cholesterol ether.
Uchegbu
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IF
Centre for Drug Delivery Research, School of Pharmacy, University of London, UK.
Schätzlein
A
A
Vanlerberghe
G
G
Morgatini
N
N
Florence
A T
AT
D002784:Cholesterol / Q000737:chemistry; D004987:Ethers / Q000737:chemistry; D018613:Microscopy, Confocal; D013501:Surface-Active Agents / Q000737:chemistry*
D004987:Ethers; D013501:Surface-Active Agents; D002784:Cholesterol