Membrane Fusion Mediated Intracellular Delivery of Lipid Bilayer Coated Mesoporous Silica Nanoparticles.

Protein delivery into the cytosol of cells is a challenging topic in the field of nanomedicine, because cellular uptake and endosomal escape are typically inefficient, hampering clinical applications. In this contribution cuboidal mesoporous silica nanoparticles (MSNs) containing disk-shaped cavities with a large pore diameter (10 nm) are studied as a protein delivery vehicle using cytochrome-c (cytC) as a model membrane-impermeable protein. To ensure colloidal stability, the MSNs are coated with a fusogenic lipid bilayer (LB) and cellular uptake is induced by a complementary pair of coiled-coil (CC) lipopeptides. Coiled-coil induced membrane fusion leads to the efficient cytosolic delivery of cytC and triggers apoptosis of cells. Delivery of these LB coated MSNs in the presence of various endocytosis inhibitors strongly suggests that membrane fusion is the dominant mechanism of cellular uptake. This method is potentially a universal way for the efficient delivery of any type of inorganic nanoparticle or protein into cells mediated by CC induced membrane fusion.