Atomic-scale detection of organic molecules coupled to single-walled carbon nanotubes

Single-walled carbon nanotubes (SWNTs) functionalized with organic molecules bearing high-scattering element tags have allowed direct visualization of modification on the atomic scale. The inclusion of these tags in protecting groups allowed their subsequent removal and reincorporation to allow visualization of corresponding protection and deprotection of organic molecules on the SWNT. This method, in conjunction with direct-Staudinger ligation of glycosyl azides to surface carboxylates allowed precise incorporation of glycans to the surface of SWNTs. Resulting glyco-SWNTs interacted successfully with carbohydrate-active enzymes for the first time, allowing elaboration of the carbohydrate structure on the surface of the SWNT and demonstrating utility of these glyco-SWNTs as potential probes. Moreover, the glycosyltransferase-catalyzed transfer of [6-H-3]-D-galactosyl to the surface of the SWNT allowed site-selective radiolabeling.