Interactions Between Amino Acid‐Tagged Naphthalenediimide and Single Walled Carbon Nanotubes for the Design and Construction of New Bioimaging Probes

Abstract

A new synthetic route to functionalized single walled carbon nanotubes (SWNTs) via supramolecular interactions using a specifically designed naphthalenediimide (NDI) nanoreceptor is demonstrated. The tendency of the NDI to spontaneously form composites with carbon nanomaterials leads to fluorescent amino acid tagged SWNTs, which are dispersible in widely accessible organic solvents (CHCl 3 , DMSO) as well as in biocompatible cell medium (EMEM, Eagle's modified essential medium). The X-ray crystal structure of the first iodine-tagged and amino acid-functionalized NDI molecule, designed especially to facilitate the high resolution transmission electron microscopy (HR TEM) imaging whilst retaining its ability to self-assemble into a nanodimensional receptor in weakly polar solvents, is also described. A new hybrid material, NDI@SWNT, was prepared and characterized as dispersed in organic solvents and aqueous media and in the solid state by HR TEM, tapping mode atomic force microscopy (TM AFM), scanning electron microscopy (SEM), circular dichroism, Raman and fluorescence spectroscopies (steady-state single and two-photon techniques). We have been interested in the design and spectroscopic investigation of new nanomaterials with light emitting properties.[67] The NDI nanotubular receptor recently developed [55] should have the ability to bind via donor-acceptor interactions to carbon nanomaterials, in an analogous manner to that found in the exciting new hybrids containing perylenes in SWNTselectron acceptor composites for photovoltaic applications, reported by the groups of Hirsch [12][13][14] and Guldi.[14]We report our investigations at the formation of a new nanohybrid, denoted NDI@SWNT, in solution and on a preparative scale. We report here for the first time, the recognition and coating of the aromatic surface of ultra-purified SWNTs (provided by Thomas Swan Ltd, Elicarb SWNTs, and further steampuriffied to ensure they are free of catalytic impurities or carbonaceous materials from the nanotube synthesis, Supplementary Information) by a new iodine-and amino acid-derivatized NDI. Investigations into the properties of the new material synthesized (in bulk and in dispersions in CHCl 3 , EtOH, DMSO and serum free aqueous cell culture media such as EMEM) have been carried out by Raman, circular dichroism, FT IR, UV-vis-NIR and fluorescence spectroscopies and imaged at the nanoscale by HR TEM, SEM, EDS and TM AFM. The cellular translocation of the resulting NDI@SWNT complex was investigated by a combination of fluorescence microscopy techniques including fluorescence lifetime imaging and cytotoxicity assays (MTT) in cancerous and non-cancerous cell lines. Here we have used such techniques to probe the integrity of a new nanocomposite denoted NDI@SWNT in vitro. Such an approach could aid the future understanding of the mechanism of action of supramolecular materials at the cellular level and improve the synthetic design of nanohybrids for biomedical imaging and therapeutic applications. Results and Discussions Synthe...

Thermally Reduced Graphene Oxide Nanohybrids of Chiral Functional Naphthalenediimides for Prostate Cancer Cells Bioimaging

“…[ 31 ] Carbon nanostructure such as SWNTs complexed with NDIs seemed to be responsible for a low degree of nuclear membrane penetration. [ 33 ] The present data is in agreement without previous fi ndings, highlighting that the interaction of NDIs and PCS is robust enough to allow the distribution of NDI•coronene and NDI•TRGO complexes in the cytoplasm, by preventing the carbon-based material to cross the nuclear membrane. Although our studies proved that PCSs are responsible for quenching effects on the NDI fl uorescence, NDI•coronene and NDI • TRGO nanohybrids retain the ability to generate suitable fl uorescence emission in vitro.…”

“…[27][28][29][30] These aromatic molecules have demonstrated their capability to across cellular membranes [ 31,32 ] and favor the up-take of carbon based materials such as Single Walled Carbon Nanotubes (SWNTs). [ 33 ] Such behavior seems to be independent from the primary amine employed for the synthesis of NDIs and rather be driven by the planar naphthalene diimide cores. [31][32][33] The phenylalanine tagged NDIs demonstrate reasonable 2-photon cross-section areas [ 34 ] and despite their rather low quantum yields, can be successfully used as imaging probes in prostate cancer cell due to their broad fl uorescent emission.…”

“…[ 33 ] Such behavior seems to be independent from the primary amine employed for the synthesis of NDIs and rather be driven by the planar naphthalene diimide cores. [31][32][33] The phenylalanine tagged NDIs demonstrate reasonable 2-photon cross-section areas [ 34 ] and despite their rather low quantum yields, can be successfully used as imaging probes in prostate cancer cell due to their broad fl uorescent emission. [ 31 ] These optical properties combined with biocompatibility have rendered them ideal candidates for further functionalization and exploitation for fl uorescent bioimaging.…”

“…[ 31 ] These optical properties combined with biocompatibility have rendered them ideal candidates for further functionalization and exploitation for fl uorescent bioimaging. [ 30,31,33 ] The assembly process between NDIs and nanomaterials such as C 60 , C 70 , and SWNTs has been explored, by us and others. [ 33,[35][36][37] Recently, an interest in understanding their interactions with planar carbon system (denoted here PCS) has emerged and these are believed to be based on noncovalent contacts such as π-stacking coupled with hydrophobic interactions and Coulombic attractions of the electron deficient NDI core to the electron rich surface of graphene and its derivatives.…”

“…[ 30,31,33 ] The assembly process between NDIs and nanomaterials such as C 60 , C 70 , and SWNTs has been explored, by us and others. [ 33,[35][36][37] Recently, an interest in understanding their interactions with planar carbon system (denoted here PCS) has emerged and these are believed to be based on noncovalent contacts such as π-stacking coupled with hydrophobic interactions and Coulombic attractions of the electron deficient NDI core to the electron rich surface of graphene and its derivatives. [ 38 ] Zhang et al [ 39 ] demonstrated the ability of NDIs to interact with allotropes of carbon on a supramolecular level by showing the improved dispersion stability of graphene in water when complexed with N , N ′-bis-[2-(ethanoic acid sodium)]-NDI after exfoliation of sheets of graphene by sonication.…”