Vesicular Lipidic Systems, Liposomes, PLO, and Liposomes–PLO: Characterization by Electronic Transmission Microscopy

Abstract

Situations exist in which rapid administration of treatment, as well as maintenance of efficient concentrations for the longest possible time, turns out to be essential. In view of the previous treatment, the elaboration of liposomes, PLO (pluronic lecithin organogel), and the mixture of both is described, as well as their characterizations by electronic transmission microscopy, with the aim of finding out precisely the type of structure for both controlled release systems, its composition, size, homogeneity, and integrity. The period of study has been 90 days. Multilaminar and unilaminar vesicles smaller than 1 μm in diameter were seen in the liposomes, PLO, and liposomes–PLO formulations on transmission electron microscopic (TEM) observation. The technique of characterization reveals the progressive aggregation of the liposomas along the period of study. However, all the vesicles of PLO maintain a defined structure and only a light aggregation 60 days after the elaboration. Changes of morphology and aggregation of liposomas decreased after the incorporation of cholesterol (CH) to the liposomal matrix. The best results were obtained with the formulas liposomes–PLO, which maintain their individuality and integrity during the whole period of study. The combined formulation of liposomas and PLO showed an increase of stability of both lipid systems.

Keywords:

• liposomes
• PLO
• transdermal
• reservoir effect
• controlled release

ACKNOWLEDGMENTS

Part of this work was supported by MEC Spain and Feder founds, under Project MAT 2005-07746C02-02 02 and project of Excellence FQM 410.