Novel Small Multilamellar Liposomes Containing Large Quantities of Peptide Nucleic Acid Selectively Kill Breast Cancer Cells

Abstract

Peptide nucleic acid (PNA) may be used in various biomedical applications; however, these are currently limited, due to its low solubility in aqueous solutions. In this study, a methodology to overcome this limitation is demonstrated, as well as the effect of PNA on cell viability. We show that extruding a mixture of natural phospholipids and short (6–22 bases), cytosine-rich PNA through a 100 nm pore size membrane under mild acidic conditions resulted in the formation of small (60–90 nm in diameter) multilamellar vesicles (SMVs) comprising several (3–5) concentric lipid membranes. The PNA molecules, being positively charged under acidic conditions (due to protonation of cytosine bases in the sequence), bind electrostatically to negatively charged phospholipid membranes. The large membrane surface area allowed the encapsulation of thousands of PNA molecules in the vesicle. SMVs were conjugated with the designed ankyrin repeat protein (DARPin_9-29), which interacts with human epidermal growth factor receptor 2 (HER2), overexpressed in human breast cancer. The conjugate was shown to enter HER2-overexpressing cells by receptor-mediated endocytosis. PNA molecules, released from lysosomes, aggregate in the cytoplasm into micron-sized particles, which interfere with normal cell functioning, causing cell death. The ability of DARPin-functionalized SMVs to specifically deliver large quantities of PNA to cancer cells opens a new promising avenue for cancer therapy.

Ultrasmall ATP-Coated Gold Nanoparticles Specifically Bind to Non-Hybridized Regions in DNA

“…To reduce viability, the particles should be specifically delivered into the pathological cells. This can be done, in particular, by encapsulation of the particles in receptor-targeted liposomes, followed by delivery of the cargo vesicles into the cell, an experimental strategy that we have used before for delivering various bio-active compounds into cancer cells [57,58]. ATP-NPs are small enough to enter the cell nucleus from the cytoplasm by passive diffusion.…”

Cationic Calix[4]arene Vectors to Efficiently Deliver AntimiRNA Peptide Nucleic Acids (PNAs) and miRNA Mimics

“…PNAs are particularly suited for this purpose thanks to their neutral, pseudopeptide backbone that imparts them with inertness towards nuclease and peptidase enzymes, and a remarkable affinity and selectivity for complementary targets [ 22 , 23 ]. These features have been exploited in cancer cellular models (i.e., colorectal cancer, glioma, glioblastoma, breast cancer, leukemia) [ 24 , 25 , 26 , 27 , 28 , 29 ] and genetic diseases (i.e., cystic fibrosis) [ 30 ]. PNAs were even found to be effective for some in vivo application [ 31 , 32 ].…”