New mechanisms for non-porative ultrasound stimulation of cargo delivery to cell cytosolwith targeted perfluorocarbon nanoparticles

Abstract

The cell membrane constitutes a major barrier for non-endocytotic intracellular delivery oftherapeutic molecules from drug delivery vehicles. Existing approaches to breaching the cellmembrane include cavitational ultrasound (with microbubbles), electroporationand cell-penetrating peptides. We report the use of diagnostic ultrasound forintracellular delivery of therapeutic bulky cargo with the use of molecularly targetedliquid perfluorocarbon (PFC) nanoparticles. To demonstrate the concept, we useda lipid with a surrogate polar head group, nanogold-DPPE, incorporated intothe nanoparticle lipid monolayer. Melanoma cells were incubated with nanogoldparticles and this was followed by insonication with continuous wave ultrasound(2.25 MHz, 5 min, 0.6 MPa). Cells not exposed to ultrasound showed gold particlespartitioned only in the outer bilayer of the cell membrane with no evidence of theintracellular transit of nanogold. However, the cells exposed to ultrasound exhibitednumerous nanogold-DPPE components inside the cell that appeared polarizedinside intracellular vesicles demonstrating cellular uptake and trafficking. Further,ultrasound-exposed cells manifested no incorporation of calcein or the release of lactatedehydrogenase. These observations are consistent with a mechanism that suggests thatultrasound is capable of stimulating the intracellular delivery of therapeutic moleculesvia non-porative mechanisms. Therefore, non-cavitational adjunctive ultrasoundoffers a novel paradigm in intracellular cargo delivery from PFC nanoparticles.