Lipid Composition-Driven Colloidal Transformation from Hexosomes to Nanoparticles with Highly Disordered Internal...

Nonlamellar liquid crystalline nanodispersions produced from single monoacylglycerols or from their combinations with fatty acids or other amphiphiles have attracted interest owing to their structural versatility and tunability. In this study, we investigated the effect of dilinolein (DLO) incorporation on the structural features of Pluronic F127-stabilized monolinolein (MLO) nanodispersions using small-angle X-ray scattering (SAXS), cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS). We report a lipid composition-dependent direct colloidal transformation from hexosomes, defined as nanoparticles with an ordered internal inverse hexagonal (H₂) phase, toward nanoparticles with highly disordered internal nanostructures upon the partial replacement of MLO by DLO. Small-angle X-ray scattering (SAXS) measurements showed that, at relatively low DLO content, the MLO-rich MLO:DLO 90:10 (w/w) nanodispersion retained an ordered internal H₂ phase, with three well-defined characteristic Bragg peaks, whereas the SAXS patterns recorded for nanodispersions containing ≥20 wt% DLO displayed loss of the characteristic H₂ Bragg reflections and broad correlation maxima, indicating loss of long-range internal periodicity and the emergence of highly disordered internal nanostructures. Similarly, the control nanodispersion prepared from DLO alone displayed a broad, low-intensity correlation maximum rather than distinct Bragg peaks, consistent with a highly disordered internal nanostructure. For the nanodispersions displaying broad SAXS correlation maxima, the SAXS-derived characteristic distance decreased monotonically from 4.53 to 2.87 nm as the DLO fraction increased. Additional cryo-TEM observations of two nanodispersions containing relatively high DLO contents revealed predominantly spherical nanoparticles characterized by an intense lipid core and discernible internal nanoscale features. However, these internal features were not sufficiently resolved to allow full characterization and unambiguous assignment of the internal phase, consistent with a highly disordered inverse nanostructure that may include an L₂-like inverse-micellar organization alongside other possible arrangements such as nanoemulsion droplets. Taken together, the SAXS and cryo-TEM observations indicate a composition-driven colloidal transformation from hexosomes with a well-defined internal H₂ phase toward nanoparticles with a highly disordered internal phase as the DLO content increases. The experimental findings suggest that DLO modifies lipid packing at the MLO-water interface and promotes more negative spontaneous curvature, favoring the observed structural transformation. The ability to tune the internal nanostructure by lipid composition while maintaining nanoscale particle size and low dispersity makes these nanodispersions attractive platforms for drug nanocarrier development.