Cold field emission gun-scanning electron microscopy: a new tool for morphological and ultrastructural analysis of liposomes.
Liposomes are lipid vesicles largely investigated in the past 30 years as pharmaceutical carriers. In the development of new liposome-based formulations, the study of liposome surface properties remains a crucial step. For this purpose, microscopy techniques can provide useful information, although each such technique suffers from some limitations. Here, we have used cold field emission gun-scanning electron microscopy (cFEG-SEM) to acquire detailed images of liposome surface. In particular, we observed PEGylated and non-PEGylated liposomes in different size ranges. In the case of nanosized liposomes (mean diameter about 200 nm), a morphological evaluation of the whole preparation was obtained. On the other hand, in the case of giant liposomes (mean diameter about 2 microm), it was possible to observe the different surface ultrastructures of the two formulations. In particular, a regular and only slightly wrinkled surface was observed in the case of non-PEGylated liposomes, while a very irregular surface ultrastructure was visible in the case of PEGylated liposomes. This study shows, for the first time, the potential of cFEG-SEM as a new and powerful tool to obtain information on liposome morphology and, at least in the case of giant liposomes, on ultrastructure of the liposome surface.
De Rosa
G
G
Dipartimento di Chimica Farmaceutica e Tossicologica, Facoltà di Farmacia, Università degli studi di Napoli Federico II, Via Domenico Montesano 49, 80131 Napoli, Italy. gderosa@unina.it
De Stefano
M
M
Ungaro
F
F
La Rotonda
M I
MI
D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry; D013499:Surface Properties
D008051:Lipid Bilayers; D008081:Liposomes