NONIONIC SURFACTANT BASED VESICLES (NIOSOMES) IN DRUG-DELIVERY

The self assembly of non-ionic surfactants into vesicles was first rep orted in the seventies by researchers in the cosmetic industry. Since then a number of groups world wide have studied non-ionic surfactant v esicles (niosomes) with a view to evaluating their potential as drug c arriers. This article presents a summary of the achievements in the fi eld to date. Niosomes may be formed form a diverse array of amphiphile s bearing sugar, polyoxyethylene, polyglycerol, crown ether and amino acid hydrophilic head groups and these amphiphiles typically possess o ne to two hydrophobic alkyl, perfluoroalkyl or steroidal groups. The s elf assembly of surfactants into niosomes is governed not only by the nature of the surfactant but by the presence of membrane additives, th e nature of the drug encapsulated and the actual method of preparation . Methods of niosome preparation and the number of different morpholog ies that have been identified are detailed. The influence of formulati on factors on niosome stability is also examined as are methods to opt imise drug loading. In vivo these systems have been evaluated as immun ological adjuvants, anti-cancer/anti-infective drug targeting agents a nd carriers of anti-inflammatory drugs. Niosomes have also been used i n diagnostic imaging. Efforts to achieve transdermal and ophthalmic dr ug delivery with some formulations are also discussed. (C) 1998 Elsevi er Science B.V. All rights reserved.