Topology and internal structure of PEGylated lipid nanocarriers for neuronal transfection: synchrotron radiation SAXS and cryo-TEM studies

Towards potential treatment of neurodegenerative disorders by nanomedicine gene therapy, a nonviral gene delivery system is created by complexation of novel PEGylated cationic lipid assemblies and a plasmid DNA encoding for the protein brain-derived neurotrophic factor (BDNF). The generated monoolein-based liquid crystalline nanocarriers for BDNF gene transfer are characterized by means of small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) techniques. The complexation of the BDNF plasmids (pBDNF) to the positively charged lipid nanocarriers, is directly detected by turbidity measurements. Morphologically variable populations of sterically stabilized, PEGylated multicompartment nanoobjects, with confined supercoiled DNA, are established by cryo-TEM imaging. Synchrotron radiation SAXS measurements, performed with diluted nanoparticulate dispersions, evidence the inner multilamelar structure of pear-type vesicles and flexible onion-like objects functionalized by pBDNF. The experimental SAXS intensity curves are fitted with a scattering model for multilamellar vesicles involving five lamellas. As the monoolein-based multicompartment nanocarriers can strongly affect the organization of targeted membranes, the obtained structural data are of fundamental interest for improvement of brain-targeted gene delivery and understanding of cellular internalization mechanisms of nanocarriers in neuronal transfection studies.