Abstract
The hydration of phospholipids, electrospun into polymeric nanofibers and used as templates for liposome formation, offers pharmaceutical advantages as it avoids the storage of liposomes as aqueous dispersions. The objective of the present study was to electrospin and characterize amphiphilic nanofibers as templates for the preparation of antibiotic-loaded liposomes and compare this method with the conventional film-hydration method followed by extrusion. The comparison was based on particle size, encapsulation efficiency and drug-release behavior. Chloramphenicol (CAM) was used at different concentrations as a model antibacterial drug. Phosphatidylcoline (PC) with polyvinylpyrrolidone (PVP), using ethanol as a solvent, was found to be successful in fabricating the amphiphilic composite drug-loaded nanofibers as well as liposomes with both methods. The characterization of the nanofiber templates revealed that fiber diameter did not affect the liposome size. According to the optical microscopy results, the immediate hydration of phospholipids deposited on the amphiphilic nanofibers occurred within a few seconds, resulting in the formation of liposomes in water dispersions. The liposomes appeared to aggregate more readily in the concentrated than in the diluted solutions. The drug encapsulation efficiency for the fiber-hydrated liposomes varied between 14.9 and 28.1% and, for film-hydrated liposomes, between 22.0 and 77.1%, depending on the CAM concentrations and additional extrusion steps. The nanofiber hydration method was faster, as less steps were required for the in-situ liposome preparation than in the film-hydration method. The liposomes obtained using nanofiber hydration were smaller and more homogeneous than the conventional liposomes, but less drug was encapsulated.
Highlights
Mean fiber diameters and diameter size distributions were measured by Scanning electron microscopy (SEM), since it was hypothesized that fiber diameter may significantly affect the size of the formed liposomes during the hydration step
We varied the amounts of PC and CAM, and in order to have reproducibly successful electrospinning with different formulations, PVP
The liposomes self-assembled during the hydration phase, but the results confirmed that their liposome-formation mechanisms differ
Summary
Licensee MDPI, Basel, Switzerland.Attribution (CC BY) license (https://creativecommons.org/licenses/by/ 4.0/).Liposomes are spherical vesicles consisting of an aqueous core surrounded by one or several phospholipid bilayers. Liposomes have played a major role in drug delivery research and product development as part of nanomedicine. One of the biggest challenges in liposome preparation is obtaining a product which has a monodispersed size distribution and decent stability [1]. Increasingly important are the issues related to scaling-up for industrial production and scaling-down for point-of-care applications, which have motivated improvements to the conventional processes and have also led to the development of Pharmaceutics 2021, 13, 1742. https://doi.org/10.3390/pharmaceutics13111742 https://www.mdpi.com/journal/pharmaceutics
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