Abstract
The gold nanoparticle (GNP) aggregation growth induced by deoxyribonucleic acid (DNA) is studied by laser scanning confocal and environmental scanning electron microscopies. As in the investigated case the direct light scattering analysis is not suitable, we observe the behavior of the fluorescence produced by a dye and we detect the aggregation by the shift and the broadening of the fluorescence peak. Results of laser scanning confocal microscopy images and the fluorescence emission spectra from lambda scan mode suggest, in fact, that the intruding of the hydrophobic moiety of the probe within the cationic surfactants bilayer film coating GNPs results in a Förster resonance energy transfer. The environmental scanning electron microscopy images show that DNA molecules act as template to assemble GNPs into three-dimensional structures which are reminiscent of the DNA helix. This study is useful to design better nanobiotechnological devices using GNPs and DNA.
Highlights
Individual particles and assemblies of gold nanoparticles (GNPs) show different optical and electrical properties
The Surface plasmon resonance (SPR) of GNPs presents a broadening and red shift when they aggregate [22]. It seems that Nile Blue perchlorate (NB) entrapment inside the hydrophobic part of the bilayer polymeric film covering aggregated GNPs is responsible of a FRET between NB and aggregated GNPs which explains the fluorescence enhancement in the (565.59–706.59) nm range (Figure 3)
In the previous paragraph we showed that the broadening and the redshift of the fluorescence spectra of NB bound to cationic surfactants complexes was an indicator of GNPs aggregation
Summary
Individual particles and assemblies of gold nanoparticles (GNPs) show different optical and electrical properties. The development of nanobiotechnology is helped by a deep understanding of the interaction of GNPs with nucleic acids, which are used as a basic tool for nanobiotechnological devices [3,4] Examples of this approach are the organization of metal and semiconductor nanoclusters [5], several bioanalytical techniques [6], the biomolecular electronics [7] and nanomechanical systems. Confocal and two photon microscopies and single-cell plasmonically-enhanced Rayleigh-scattering imaging spectroscopy were used as imaging techniques to observe the GNPs aggregation after their accumulation within living cells through endocytosic processes [14,15,16]. These approaches take advantage of the characteristic optical properties of plasmonic. Due to the strong interaction between NB molecules and the large localized fields induced by the plasmonic coupling, a highly enhanced fluorescence is produced allowing the localization of GNPs aggregates
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