Aescin - a natural soap for the formation of lipid nanodiscs with tunable size

The saponin beta-aescin from the seed extract of the horse chestnut tree Aesculus hippocastanum has demonstrated a beneficial role in clinical therapy which is in part related to its strong interaction with biological membranes. In this context the present work investigates the self-assembly of nm-sized discoidal lipid nanoparticles composed of beta-aescin and the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The discoidal lipid nanoparticles reassemble from small discs into larger discs, ribbons and finally stacks of sheets upon heating from gel-phase to fluid phase DMPC. The morphological transition of the lipid nano-particles is mainly triggered by the phospholipid phase state change. The final morphology depends on the phospholipid-to-saponin ratio and the actual temperature. The study is conducted by small-angle X-ray scattering (SAXS) and transmission (TEM) and freeze fracture electron microscopy (FFEM) are used to cover larger length scales. Two different models, representing a disc and ribbon-like shape are applied to the SAXS data, evaluating possible geometries and molecular mixing of the nano-particles. The stacked sheets are analysed by the Caille theory.

Automated summary

The study investigates the self-assembly and morphological transition of nm-sized discoidal lipid nanoparticles composed of beta-aescin and the phospholipid DMPC. The transition of the lipid nanoparticles is mainly triggered by the phase state change of the phospholipid, resulting in different final morphologies depending on the phospholipid-to-saponin ratio and temperature. Techniques like SAXS, TEM, and FFEM are used to analyze the nano-particles at different length scales, with models applied to evaluate possible geometries and molecular mixing.