Lipid sponge phase nanoparticles (L 3 NPs) are emerging as versatile carriers for biomolecular delivery due to their curved flexible bilayer structures and their interconnected relatively large (>10 nm) aqueous channels. Similar structures can also be found in cell organelles. L 3 NPs are bicontinuous nanostructures that enable efficient encapsulation of large, sensitive biomolecules, including proteins. However, scalable production methods and mechanistic insights into their membrane interactions remain under explored. We use a microfluidic approach to fabricate L 3 NPs, based on mixtures of acyl glycerides and phospholipids, with and without the heme protein myoglobin (Mb). Their structural features and interfacial behavior at model lipid biomembranes were explored by using scattering, microscopy and surface-sensitive techniques. By using neutron reflectometry and different isotopic contrast, i.e., H 2 O and D 2 O buffers and deuterated lipids, we could separate between the different components, i.e., lipids and protein. Both lipids and protein cargo (Mb) from the L 3 NPs exchange with a model POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) biomembrane. Notably, while lipid exchange is evident, the overall integrity of the POPC bilayer is preserved. Electrochemical impedance spectroscopy measurement results suggest that the L 3 NPs do not induce substantial leakage of the model biomembrane. These findings provide valuable insight for optimizing protein encapsulation and controlling release mechanisms of sponge phase delivery systems.
Machingauta et al. (Sun,) studied this question.