Articles | 2006

Advanced Functional Materials, 2006, 16(14): 1839-1846

Luminescence of functionalized carbon nanotubes as a tool to monitor bundle formation and dissociation in water: the effect of plasmid-DNA (pDNA) complexation

L. Lacerda, G. Pastorin, W. Wu, M. Prato, A. Bianco, K. Kostarelos

Functionalized carbon nanotubes (f-CNTs) are explored as novel nanomaterials for biomedical applications. UV-vis luminescence of aqueous dispersions of CNT–NH3 + and CNT–NH–Ac (NH–Ac: acetamido) is observed using standard laboratory spectrophotometric instrumentation, and the measured fluorescence intensity is correlated with the aggregation state of the f-CNTs: a high intensity indicates improved f-CNT individualization and dispersion, while a decrease in fluorescence intensity indicates a higher degree of nanotube aggregation and bundling as a result of varying the sodium dodecyl sulfate (SDS) concentrations and pH in the aqueous phase. Moreover, utilization of this relationship between fluorescence intensity and the state of f-CNT aggregation is carried out to elucidate the interactions between f-CNTs and gene-encoding plasmid DNA (pDNA). pDNA is shown to interact with CNT–NH3 + primarily through electrostatic interactions that lead concomitantly to a higher degree of f-CNT bundling.  The CNT–NH3+/pDNA interactions are successfully competed by SDS/f-CNT surface interactions, resulting in the displacement of pDNA. These studies provide exemplification of the use of fluorescence spectrophotometry to accurately describe the aggregation state of water-soluble f-CNTs. Characterization of the complexes between pDNA and f-CNTs elucidates the opportunities and limitations of such supramolecular systems as potential vectors for gene transfer.

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