The encapsulation and release of peptides, proteins, nucleic acids, and drugs in nanostructured lipid carriers depend on the type of the self-assembled liquid-crystalline organization and the structural dimensions of the aqueous and membraneous compartments, which can be tuned by the multicomponent composition of the systems. In this work, small-angle X-ray scattering (SAXS) investigation is performed on the ‘melting’ transition of the bicontinuous double diamond cubic phase, formed by pure glycerol monooleate (MO), upon progressive inclusion of varying fractions of pharmaceutical-grade glycerol monooleate (GO) in the hydrated system. The self-assembled MO/GO mixtures are found to form diamond (Pn3m) inverted cubic, inverted hexagonal (H_II), and sponge (L₃) phases at ambient temperature in excess of aqueous medium without heat treatment. Mixing of the inverted-cubic-phase-forming MO and the sponge-phase-forming GO components, in equivalent proportions (50/50 w/w), yields an inverted hexagonal (H_II) phase nanostructured carrier. Scattering models are applied for fitting of the experimental SAXS patterns and identification of the structural changes in the aqueous and lipid bilayer subcompartments. The possibility of transforming, at ambient temperature (20 °C), the bicontinuous cubic nanostructures into inverted hexagonal (H_II) or sponge (L₃) mesophases may facilitate novel biomedical applications of the investigated liquid crystalline self-assemblies.

Many phytochemical antioxidant compounds, including curcumin (CU), are water-insoluble and thus require delivery carriers in order to increase their bioavailability for in vivo applications. Oxidative stress-related apoptosis is a common cause for the neuronal loss in the progression of neurodegenerative diseases. Lipid nanoparticles (NPs) with internal self-assembled liquid crystalline structures present strong interest as safe drug delivery systems for neuronal regeneration through combination therapies. Here, we report spongosome and cubosome lipid NPs, which co-encapsulate CU and fish oil (FO), rich in ω-3 polyunsaturated fatty acids. The performed structural investigation by synchrotron small-angle X-ray scattering evidenced the liquid crystalline organization of the self-assembled NPs. The encapsulation efficiency for CU in the lipid nanocarriers was found to be higher as compared to that reported for polymer-based carriers. The cytotoxicity of the blank and antioxidant-loaded nanocarriers was negligible at lipid concentrations 300 and 500 nM. Morphological changes were observed for neuronally derived human SH-SY5Y cells subjected to damage by reactive oxygen species (ROS) upon exposure to hydrogen peroxide. Using flow cytometry, we quantified the effects of CU and FO, co-encapsulated in spongosome and cubosome lipid NPs on the response of differentiated SH-SY5Y cells to H₂O₂-induced oxidative stress. Measurements of the intracellular ROS levels (using a 2′,7′-dichlorodihydrofluorescein diacetate probe) and of apoptotic cells (using an Annexin V-PE/SYTOX-green assay) were performed to compare the neuroprotective potential of the liquid crystalline spongosome and cubosome nanocarriers to that of ethanolic solutions or aqueous suspensions of the CU/FO mixtures. The results indicated that dual drug-loaded cubosomes may be suitable for combination treatments against neurodegenerative disorders.