Macromolecular cytosolic delivery: cell membranes as the primary obstacle

Fluorogenic label to quantify the cytosolic delivery of macromolecules

The delivery of a macromolecule to the cytosol of human cells is assessed by using a pendant di-O-glycosylated derivative of fluorescein. Its fluorescence is unmasked by Escherichia coliβ-galactosidase installed in the cytosol. Background is diminished by using RNAi to suppress the expression of GLB1, which encodes a lysosomal β-galactosidase. This strategy was used to quantify the cytosolic entry of a highly cationic protein, ribonuclease A.

Enhanced plasmid DNA delivery using anionic LPDII by listeriolysin O incorporation

BACKGROUND

A major obstacle to achieving effective DNA-based therapeutics is efficient delivery of the DNA to its site of action in the cell. Upon internalization by endocytosis, the endosomal membrane represents a critical physical barrier preventing access of DNA to the cell cytosol. In order to overcome the membrane barrier and facilitate cytosolic entry, the endosomolytic bacterial protein listeriolysin O (LLO) is a potentially promising agent.

METHODS

LLO was incorporated in an anionic liposome-entrapped polycation-condensed DNA delivery system (LPDII). Plasmid DNA was condensed using protamine sulfate and then complexed to anionic liposomes. LLO was incorporated into the delivery vehicle through encapsulation in anionic, pH-sensitive liposomes. Transfection levels were monitored using a model reporter plasmid encoding luciferase in P388D1 cells, a macrophage-like cell line.

RESULTS

Transfection using the anionic LPDII delivery platform was enhanced through incorporation of LLO. Additionally, the net charge of the condensate, the lipid composition, and the total amount of LLO-liposomes were all capable of modulating the transfection levels of the vehicle. Importantly, in the presence of serum, transfection levels using the LLO-containing LPDII system were comparable to established cationic lipid delivery systems.

CONCLUSIONS

LLO is capable of facilitating transfection using an anionic LPDII system. This anionic delivery vehicle represents the successful combination of the LPDII system for condensation of the DNA with the unique endosomolytic properties of LLO for improved transfection using plasmid DNA.