Facilitating Non-Covalent Interactions: 'Nanoglue' for DNA-CNT Nanohybrid Complexes

Polyamine-terminated first and second generation Newkome dendrimers possessing a perylene core were synthesised. Interactions were probed between carbon nanotubes and the perylene core. The DNA binding ability of the dendrimers was tested. As with similar, non polyamine terminated perylene containing dendrimers reported in the literature, the first generation dendrimer was shown to solubilise carbon nanotubes. The first generation dendrimer demonstrated a particularly high DNA binding ability, presumably in part due to covalent and self-assembled multivalency. Theory and observations gave cause for concern regarding the applicability of the ethidium bromide displacement DNA binding assay to systems containing polycyclic aromatic hydrocarbons, due to the possibility of intercalation into the DNA double-helix. This alternate binding mode was investigated. The second generation dendrimer exhibited slightly reduced binding ability relative to its cationic charge, in opposition to the increase in binding strength that would be expected due to increased covalent multivalency, but in accordance with a reduction in intercalation and self-assembled multivalency. Difficulty was experienced imaging DNA by transmission electron microscopy; accordingly no direct evidence could be produced to demonstrate the existence of DNA dendrimer CNT nano-hybrids. However, the data indicating the formation of CNT-dendrimer complexes and dendrimer-DNA complexes suggest that, in solution, DNA dendrimer CNT nano-hybrids should be present. No evidence could be found to suggest that binding of the dendrimer molecules to carbon nanotubes significantly reduced their affinity for DNA, nor to suggest that binding of the dendrimers to DNA significantly inhibited their CNT binding ability.