Multifunctional envelope-type nano device (MEND) for organelle targeting via a stepwise membrane fusion process

A single cell contains a variety of organelles. Included among these organelles are the nucleus that regulates the central dogma, mitochondria that function as an energy plant, the Golgi apparatus that determines the destination of endogenous protein, and others. If it were possible to prepare a nano craft that could specifically target a specific organelle, this would open a new field of research directed toward therapy for various diseases. We recently developed a new concept of "Programmed Packaging," by which we succeeded in creating a multifunctional envelope-type nano device (MEND) as a nonviral gene-delivery system. Our attempts to target certain organelles (nucleus and mitochondria) are described here, mainly focusing on the construction of a tetra-lamellar MEND (T-MEND), and on methods for screening the organelle-specific fusogenic envelope. The critical structural elements of the T-MEND include an organelle-specific membrane-fusogenic inner envelope and a cellular membrane-fusogenic outer envelope. The resulting T-MEND can be utilized to overcome intracellular membrane barriers, since it involves stepwise membrane fusion. To deliver cargos into a target organelle in our strategy, the carriers must fuse with the organelle membrane. Therefore, we screened a series of lipid envelopes that have the potential for fusing with an organelle membrane by monitoring the inhibition of fluorescence resonance energy transfer and identified the optimal lipid conditions for nuclear and mitochondrial membrane fusion. Finally, we describe the delivery of a bioactive molecule targeted to the nucleus and mitochondria in living cells, demonstrating that this system can be useful for targeting various organelles.