Incorporation of antimicrobial peptides in nanostructured lipid membrane mimetic bilayer cubosomes.

The inverse bicontinuous lipidic cubic phase offers a simple and robust membrane mimetic with the ability to encapsulate peptides, potentially increasing bioavailability, while also offering a platform from which functionalized, targeted nanoparticles can be developed. Herein we have investigated the use of a number of cubic phase nanoparticle systems with encapsulated antimicrobial peptides gramicidin A', melittin, and alamethicin. The optimal peptide loading ranges, over which cubic symmetry was retained, were determined using small angle X-ray scattering. A large variation in peptide loading capability of different cubosome formulations was confirmed using circular dichroism. Observations are supported by particle sizing using dynamic light scattering as well as by direct visualization of nanoparticle morphology using cryogenic transmission electron microscopy. The results are discussed in relation to bilayer properties such as the hydrophobic mismatch between bilayer and peptide, intrinsic surface curvature, and lateral pressure profile of each lipid system. The findings of this study should be of use in the further development of lipid-based peptide encapsulation systems, particularly in the field of drug delivery.