RESUMEN
Organic functionalization of carbon nanotube sidewalls is a tool of primary importance in material science and nanotechnology, equally from a fundamental and an applicative point of view. Here, an efficient and versatile approach for the organic/organometallic functionalization of single-walled carbon nanotubes (SWCNTs) capable of imparting multimodality to these fundamental nanostructures, is described. Our strategy takes advantage of well-established Cu-mediated acetylene-azide coupling (CuAAC) reactions applied to phenylazido-functionalized SWCNTs for their convenient homo-/heterodecoration with a number of organic/organometallic frameworks, or mixtures thereof, bearing terminal acetylene pendant arms. Phenylazido-decorated SWCNTs were prepared by chemoselective arylation of the CNT sidewalls with diazonium salts under mild conditions, and subsequently used for the copper-mediated cycloaddition protocol in the presence of terminal acetylenes. The latter reaction was performed in one step by using either single acetylene derivatives or equimolar mixtures of terminal alkynes bearing either similar functional groups (masked with orthogonally cleavable protecting groups) or easily distinguishable functionalities (on the basis of complementary analytical/spectroscopic techniques). All materials and intermediates were characterized with respect to their most relevant aspects/properties by TEM microscopy, thermogravimetric analysis coupled with MS analysis of volatiles (TG-MS), elemental analysis, cyclic voltammetry (CV), Raman and UV/Vis spectroscopy. The functional loading and related chemical grafting of both primary amino- and ferrocene-decorated SWCNTs were spectroscopically (UV/Vis, Kaiser test) and electrochemically (CV) determined, respectively.
RESUMEN
D-(-)-Lentiginosine [(-)-4], the nonnatural enantiomer of the iminosugar indolizidine alkaloid L-(+)-lentiginosine, acts as apoptosis inducer on tumor cells of different origin, in contrast to its natural enantiomer. Although D-(-)-4 exhibited a proapoptotic activity towards tumor cells at level lower than the chemotherapeutic agent, SN38, it was less proapoptotic towards normal cells and less cytotoxic. Apoptosis induced by D-(-)-4 was caspase-dependent, as shown by the increased expression and activity of caspase-3 and -8 in treated cells, and by inhibition following treatment with the pan caspase inhibitor, ZVAD-FMK. This study highlighted how a natural iminosugar alkaloid and its synthetic enantiomer, which were simply known for their inhibition against a fungal glucoamylase, could behave in a complete different way when tested towards cell growth and death of cells of different origin.