Cargo and Carrier Effects of Rapamycin-Loaded Perfluorocarbon Nanoparticles

Nanoparticle-based drug delivery has been championed as a means to increase local delivery of therapeutics while decreasing systemic drug exposure. By targeting the particles, and therefore the drugs, to diseased cells of interest, healthy cells will be spared and side effects avoided. This delivery mechanism would be particularly useful for drugs that interfere with cell growth and proliferation pathways, as blocking proliferation in normal cells leads to significant patient morbidity. Rapamycin is a macrolide and a known inhibitor of mTORC1, a protein complex that plays a crucial role in protein translation and cell growth. This work demonstrates the effects of rapamycin complexed with a nanoparticle carrier on two distinct pathologies: a new triple negative breast cancer cell line and a conventional mouse model of muscular dystrophy (mdx). Rapamycin is able to alter mitochondrial function and thus metabolism in both free and nanoparticle-delivered form without killing the cells. Although nanoparticles are considered to be a benign carrier, this work shows that perfluorocarbon nanoparticles are able to induce autophagy in vitro. The benefits of autophagy induction in cancer cells is cell and stage specific, but has been reported to be useful for radiosensitization of triple negative breast cancers. Additionally, the particles are shown to induce autophagy in the mdx model of Duchenne Muscular Dystrophy and, when loaded with rapamycin, dramatically improve strength even in older animals with muscular dystrophy. Overall, this work enhances our understanding of the cellular effects of perfluorocarbon nanoparticles in two different disease models and enhances prospects for clinical translation of nanoparticle-based drug delivery.