Self-assembly of single-stranded RNA on carbon nanotube: polyadenylic acid to form a duplex structure.

All messenger-RNA (mRNA) molecules in eukaryotic cells have a polyadenylic acid [poly(rA)] tail at the 3'-end and human poly(rA) polymerase (PAP) has been considered as a tumor-specific target. A ligand that is capable of recognizing and binding to the poly(rA) tail of mRNA might interfere with the full processing of mRNA by PAP and can be a potential therapeutic agent. We report here for the first time that single-walled carbon nanotubes (SWNTs) can cause single-stranded poly(rA) to self-structure and form a duplex structure, which is studied by UV melting, atomic force microscopy, circular dichroism spectroscopy, and NMR spectrometry. SWNTs have shown potential applications that range from nanodevices, gene therapy, and drug delivery to membrane separations. Our studies may provide new insights into the application of SWNTs under physiological conditions, possibly being used as probes that target specific gene sequences.