Gold Branched Nanoparticles for Cellular Treatments

Abstract

Under the action of near-infrared radiation, shape anisotropic gold nanoparticles emit two-photon luminescence and release heat. Accordingly, they have been proposed for imaging, photothermal therapies and thermo-controlled drug delivery. In all these applications particular care must be given to control the nanoparticle − cell interaction and the thermal efficiency of the nanoparticles, while minimizing their intrinsic cytotoxicity. We present here the characterization of the cell interaction of newly developed branched gold nanostars, obtained by laurylsulfobetaine-driven seed-growth synthesis. The study provides information on the size distribution, the shape anisotropy, the cellular uptake and cytotoxicity of the gold nanostars as well as their intracellular dynamic behavior by means of two-photon luminescence imaging, fluorescence correlation spectroscopy and particle tracking. The results show that the gold nanostars are internalized as well as the widely used gold nanorods and are less toxic under prolonged treatments. At the same time they display remarkable twophoton luminescence and large extinction under polarized light in the near-infrared region of the spectrum, 800−950 nm. Gold nanostars appear then a valuable alternative to other elongated or in-homogeneous nanoparticles for cell imaging.

Thermal and Chemical Stability of Thiol Bonding on Gold Nanostars

“…The faster component can be ascribed to the heat exchange within the irradiated suspension. 59 The overall increase in the suspension temperature has a linear dependence on the irradiation intensity <I>; however, we observed a reduced dependence of the temperature increase in the GNS concentration ( Figure 4B): the slope ∂ΔT/∂<I> changes from 5 ± 0.2 [°C·cm 2 /W] for C = 0.39 mg/mL to 15 ± 2 [°C·cm 2 /W] for C = 0.78 mg/mL and does not substantially increase upon raising the concentration to C = 1.95 mg/mL (∂ΔT/∂<I> = 17 ± 0.2 [°C·cm 2 /W]). This is likely due to the overall extinction (scattering and absorption) of the NIR radiation by the nanoparticles with a reduction of the effective radiation that can be absorbed by the GNSs.…”

Gold nanostars coated with neutral and charged polyethylene glycols: A comparative study of in-vitro biocompatibility and of their interaction with SH-SY5Y neuroblastoma cells

“…Irradiating GNS at 800 nm with a pulsed laser source results in a wide range emission with a large maximum spanning from 550 nm to 700 nm [11]. We treated cells with GNS/PEG5000 and PAH@GNS/PEGCOOH, as representatives of biocompatible and cytotoxic coated GNS, with 48 h contact time using the same concentrations as in the experiments of the preceding section.…”

“…GNS can be thus laser-irradiated through-tissues at the wavelength of their LSPR, and by exploiting their thermal relaxation [6] noninvasive localized hyperthermal antitumoral treatments have been proposed [7][8][9][10]. Finally, the emitting properties of GNS with the TPL (twophoton luminescence) technique, once excited with pulsed laser sources on their NIR LSPR, suggest their use also for in-vitro and invivo through-tissue imaging, as the emitted luminescence also falls in the biotransparent range [11]. However, as all nanoparticles, GNS cannot be sent in-vivo or in-vitro without a proper coating.…”

Gold Nanostars for Superficial Diseases: A Promising Tool for Localized Hyperthermia?

“…The NIR plasmon resonance of GNSs can be tuned in a wide NIR range up to 1250 nm by varying the axial ratio of protruding branches [18], and multiple NIR plasmon resonances can also be obtained. The NIR plasmonic resonances are characterized by excellent transduction of their absorbed light into heat [14,16]. The estimated specific absorption rate of sea urchin GNSs can reach 200 kW/g, a value that is almost two orders of magnitude larger than that typically obtained for magnetite NPs [14].…”

“…More exotic shapes have now been developed, such as nanocages, nanoprisms and nanocrescents [4]. The interaction of these NPs with the cells [3,16], their toxicity and their fate within the human body [17] are largely affected by the chemical properties (primarily polarity and charge) of their surfaces. In addition, size and shape markedly affect the in vivo behavior of the anisotropic NPs.…”