Novel non-endocytic delivery of antisense oligonucleotides

Exploitation of intracellular pH gradients in the cellular delivery of macromolecules

Most cellular components such as the cytoplasm, endosomes, lysosomes, endoplasmic reticulum, Golgi bodies, mitochondria, and nuclei are known to maintain their own characteristic pH values. These pH values range from as low as 4.5 in the lysosome to about 8.0 in the mitochondria. Given these proton gradients around a neutral pH, weak acids, and bases with a pKa between 5.0 and 8.0 can exhibit dramatic changes in physicochemical properties. These compounds can be conjugated as such to macromolecules or incorporated into polymeric or liposomal formulations to promote the efficient cellular delivery of macromolecules. Mechanistically, the carrier molecules can facilitate favorable membrane partition, membrane fusion, transient pore formation, or membrane disruption. Drug carriers equipped with such pH-sensitive triggers and switches are able to significantly enhance the cellular delivery of macromolecules in vitro. However, the successful application of these molecules for efficient delivery in vivo requires the design of noncytotoxic, nonimmunogenic, serum compatible and biochemically labile carriers, systematic analysis of their mechanisms of action, and extensive animal studies.

Shock wave-mediated molecular delivery into cells

A single shock wave generated by a shock tube is able to effectively deliver macromolecules such as fluorescein isothiocyanate-dextran into the cytoplasm of living cells without causing cytotoxicity. We report on the effect of varying the molecular weight of the dextran and the number of shock waves on the efficiency of delivery into a cancer cell line. The fraction of cells permeabilized and the total fluorescence delivered were measured by flow cytometry, and the cellular viability by a tetrazolium assay on adherent cells and these values were compared to cell permeabilization using digitonin. Shock waves can deliver molecules of up to 2000000 molecular weight into the cytoplasm of cells without toxicity and may have applications in gene therapy.