Solid lipid nanoparticles made of self-emulsifying lipids for efficient encapsulation of hydrophilic substances

In the last decades, most attention has been paid to solid lipid nanoparticles (SLN) as nanocarriers for pharmaceutical purposes due to their low toxicity, possible production on large scale and delivery of active principles by several administration routes. For example, lung delivery will necessitate direct administration, e.g. by aerosolisation, to maximize deposition into the airways and minimize systemic side effects. However, SLN based on common solid lipids preferentially incorporate lipophilic drugs, while the hydrophilic ones are loaded in low amount. To overcome this drawback, it seemed interesting to evaluate SLN based on self-emulsifying (SE) lipids, which are mixtures of lipids, surfactant and cosurfactants able to form emulsions in contact with aqueous media. Thus, we evaluated the preparation of SLN based on Gelucire® 50/13, selected as a SE lipid model, encapsulating glutathione (GSH) or proanthocyanidins occurring in grape seed extract (GSE), as hydrophilic model substances according to the melt-emulsification method. The encapsulation efficiency of such GSH- or GSE-SLN resulted satisfactory for both the hydrophilic compounds examined. However, to draw definitive conclusions on the scope and limitations of this approach based on SE lipids, further studies are necessary. Moreover, GSH- SLN were investigated for their performance in delivering the antioxidant peptide to immunocompetent fish cells, while GSE-SLN were evaluated for their possible application in the treatment of pulmonary diseases. It was found that GSH-SLN were not internalized by fish cells, while GSE-SLN showed favorable properties for lung delivery.