Formation of ssDNA nanotubes from spherical micelles and their use as a delivery vehicle for chemotherapeutics and senolytics to triple negative breast cancer cells

With its lack of commonly targeted receptors, triple negative breast cancer (TNBC) is aggressive and difficult to treat. To address this problem, nanotubes self-assembled from single stranded DNA (ssDNA)-amphiphiles were used as a delivery vehicle for doxorubicin (DOX) to target TNBC cells. Since DOX and other standard of care treatments such as radiation have been documented to induce senescence, the ability of the nanotubes to deliver the senolytic ABT-263 was also investigated. The ssDNA-amphiphiles were synthesized from a 10 nucleotide sequence attached to a dialkyl, (C₁₆)₂, tail via a C₁₂ alkyl spacer, and have been previously shown to self-assemble into hollow nanotubes and spherical micelles. Here, we demontrate that these ssDNA spherical micelles could transition into long nanotubes in the presence of excess tails. The nanotubes could then be shortened via probe sonication. The ssDNA nanotubes internalized into three different TNBC cell lines: Sum159, MDA-MB-231, and BT549, with minimal internalization in healthy Hs578Bst cells, suggesting an inherent targeting ability. Inhibition of different internalization mechanisms showed that the nanotubes internalized in the TNBC cells primarily through macropinocytosis and scavenger receptor-mediated endocytosis, both of which are upregulated pathways in TNBC. DOX was intercalated into the ssDNA nanotubes and delivered to TNBC cells. Compared to free DOX, DOX-intercalated nanotubes proved equally cytotoxic to TNBC cells. In order to demonstrate the potential for delivery of different therapeutics, ABT-263 was incorporated into the hydrophobic bilayer wall of the nanotubes and was delivered to a DOX-induced in vitro model of senescence. The ABT-263 encapsulating nanotubes demonstrated cytotoxicity to senescent TNBC cells as well as sensitization to further DOX treatment. Thus, our ssDNA nanotubes are a promising delivery vehicle that could be used for targeted delivery of therapeutics to TNBC cells.