Structural studies of lipid based nanosystems for drug delivery: X-Ray Diffraction (XRD) and Cryogenic Transmission Electron Microscopy (cryo-TEM)

Lipid based nanosystems have potential use as matrixes able to dissolve and deliver active molecules in a controlled fashion, 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) join the advantages of colloidal lipid emulsions with those of solid matrix particles. The second generation of SLN is represented by nanostructured lipid carriers (NLC), which are composed of a solid lipid matrix with a certain content of a liquid lipid phase. Another type of lipid dispersion that can provide matrixes for the sustained release of drugs is represented by monooleine aqueous dispersions (MAD). MAD are heterogeneous systems generated by the dispersion of an amphiphilic lipid, such as monoolein, in water. They are constituted of complex lyotropic liquid crystalline nanostructures like micellar, 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 informations 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.