TAT peptide on the surface of liposomes affords their efficient intracellular delivery even at low temperature and in the presence of metabolic inhibitors

TLDR

TAT peptides derived from the HIV‑1 TAT protein facilitate intracellular delivery of proteins and small colloidal particles. To achieve efficient intracellular drug and DNA delivery, the study targeted microparticulate carriers into the cytoplasm while bypassing the endocytic pathway. Liposomes were fluorescently labeled with rhodamine‑phosphatidylethanolamine or FITC‑dextran to monitor their uptake. TAT‑functionalized 200‑nm liposomes entered mouse Lewis lung carcinoma, human BT20 breast tumor, and rat H9C2 cardiac myocyte cells independent of temperature or metabolic activity, but steric hindrance of TAT contact prevented uptake, demonstrating an energy‑independent, direct cytoplasmic delivery mechanism with potential therapeutic relevance.

Abstract

To achieve an efficient intracellular drug and DNA delivery, attempts were made to target microparticulate drug carriers into cytoplasm bypassing the endocytotic pathway. TAT peptides derived from the HIV-1 TAT protein facilitate intracellular delivery of proteins and small colloidal particles. We demonstrated that relatively large drug carriers, such as 200-nm liposomes, can also be delivered into cells by TAT peptide attached to the liposome surface. Liposomes were fluorescently labeled with membranotropic rhodamine-phosphatidylethanolamine or by entrapping FITC-dextran. Incubation of fluorescent TAT liposomes with mouse Lewis lung carcinoma cells, human breast tumor BT20 cells, and rat cardiac myocyte H9C2 results in intracellular localization of certain liposomes. Steric hindrances for TAT peptide x cell interaction (attachment of TAT directly to the liposome surface without spacer or the presence of a high MW polyethylene glycol on the liposome surface) abolish liposome internalization, evidencing the importance of direct contact of TAT peptide with the cell surface. Low temperature or metabolic inhibitors, sodium azide or iodoacetamide, have little influence on the translocation of TAT liposomes into cells, confirming the energy-independent character of this process. The approach may have important implications for drug delivery directly into cell cytoplasm.