Fig. 3. Schematic representations of drug-loaded lipid vesicles (left) and nucleic acid-loaded lipid nanoparticles (LNPs)/lipoplexes (right). For drug-loaded vesicles, different types of drug molecules can be loaded through different mechanisms. For active targeting and controlled release, ligands can be attached. The dashed line indicates that vesicle surfaces can be modified to be neutral, negative, or positive; not a mix of charges on the same vesicle. For the delivery of nucleic acids, LNPs (left half) are inverted micelles whose inner cores are occupied by cationic or ionizable lipids, which are usually formed by passive loading, while lipoplexes (right half) retain the continuous bilayer structure of their precursor liposomes, which are usually formed by active loading.