Biochemical NanotubesContaining Heterocycles as ArtificialStrands for Pseudo Duplex and Triplex DNA Formation

This report presents our discoveries that include the successful hybridization of grafted single-walled carbon nanotubes (SWCNTs) with dsDNA to form pseudo triplex-DNA. These tubes are attached with distinctive five-membered N-containing heterocycles (i.e., imidazolidinone and triazolidindione) on their surface. In this study, the heterocycles play a crucial role as DNA binders. Consequently, three functionalized SWCNTs (f-SWCNTs) are synthesized, which are incorporated with multiple–phenoxy–triazole–(ethylene glycol)–(heterocycle) ligands. These f-SWCNTs are entwined with dsDNA to form “pseudo triplex”. Notably, the dsDNA disengages from the f-SWCNTs at 85 °C and then is able to revert to triplex-DNA upon temperature reduction. Additionally, these f-SWCNTs act as a complementary strand for ssDNA to form pseudo duplex-DNA, in which the base pairings therein dissociate at 55 °C. Comprehensive analysis by use of CD spectrometer, SEM, TEM, and AFM microscopy provides substantive evidence for these phenomena. The demonstrated ability to manipulate DNA liberation from pseudo duplexes and triplexes indicates the potential versatility of f-SWCNTs as effective delivery vehicles for drugs and biomaterials in gene therapy and biotechnology.