Structural studies of lipid-based nanosystems for drug delivery: X-ray diffraction (XRD) and cryogenic transmission electron microscopy (Cryo-TEM)

Lipid-based nanosystems have gained interest as matrixes able to dissolve and to control delivery of active, thereby improving their bioavailability and reducing side-effects. In particular, nanoparticles based on lipids have been widely proposed as novel drug carrier systems. For instance, solid lipid nanoparticles (SLN) add up the benefit of colloidal lipid emulsions and those of solid matrix particles. Nanostructured lipid carriers (NLC), the second generation of SLN, are a blend of a solid lipid matrix and a liquid lipid phase. Among lipid dispersion providing matrixes for the sustained release of drugs monooleine aqueous dispersions (MAD) can be mentioned. MAD are heterogeneous systems generated by the dispersion of an amphiphilic lipid, such as monoolein, in water. MAD are made by a complex lyotropic liquid crystalline nanostructures such as micelles and lamellar, hexagonal, and cubic phases. In order to characterize nanosystems, it is important to carry out detailed systematic investigations. X-ray diffraction and microscopy give information about shape, inner structure and dimensions of powders, and dispersions that could not otherwise be identified. This chapter provides an overview about the use of x-ray diffraction and cryogenic transmission electron microscopy as techniques for characterizing lipid nanosystems recently developed by our research group.