Vapor nanobubbles generated around plasmonic nanoparticles (NPs) by ultrafast laser irradiation are efficient for inducing localized damage to living cells. Killing targeted cancer cells or gene delivery can therefore be envisioned using this new technology [1,2]. The extent of the damage and its non-lethal character are linked to the size of the nanobubble. Precise understanding of the mechanisms leading to bubble formation around plasmonic nanostructures is necessary to optimize the technique. In this presentation, we present a complete model that successfully describes all interactions occurring during the irradiation of plasmonics nanostructures by an ultrafast laser of various pulse widths and fluences.
Nanoavitation is caused by the interplay between heat conduction at the NP-medium interface and non-linear plasmon-enhanced photoionization of a nanoplasma in the near-field [3-5], the former being dominant for in-resonance and the latter for off-resonance irradiation. Modeling of the whole laser-nanoparticle interaction, together with the help of the shadowgraphic imaging and scattering techniques [3-5], give valuable insight on the mechanisms of cavitation at the nanoscale, leading to possible optimization of the nanostructure for bubble-based nanomedicine applications. <p> </p>1- E. Boulais, R. Lachaine, A. Hatef, and M. Meunier, Journal of Photochemistry and Photobiology C: Photochemistry Reviews 17, 26-49 (2013). <p> </p>2- E. Bergeron, S. Patskovsky, D. Rioux, and M. Meunier, Nanoscale 7,17836-17847 (2015). <p> </p>3- E. Boulais, R. Lachaine, and M. Meunier, Nano Letters 12, 4763-4769 (2012). <p> </p>4- R. Lachaine, E. Boulais, and M. Meunier, ACS Photonics 1, 331-336 (2014). <p> </p>5- C. Boutopoulos, A. Hatef, M. Fortin-Deschênes, and M. Meunier Nanoscale 7,11758-11765 (2015).
This paper presents a complete partial differential equation based model to describe the interaction of an
ultrafast laser with a plasmonic nanostructure in water. Apart from heating the structure itself, it is shown that
this interaction also leads to the generation of a plasma in the water medium and to the production of a strong
pressure wave and a nanobubble in the vicinity of the structure. Plasma collisions and relaxation are shown
to be the main source of mechanical stress in the medium and the dominant factor for the pressure wave and
bubble creation. An all-optical technique able to detect plasmonic enhanced bubble formation and pressure wave
generation is also presented.
The gold nanoparticle (AuNP) mediated ultrashort laser cell membrane perforation has been proven as an efficient
delivery method to bring membrane impermeable molecules into the cytoplasm. Nevertheless, the underlying
mechanisms have not been fully determined yet. Different effects may occur when irradiating a AuNP with ultrashort
laser pulses and finally enable the molecule to transfer. Depending on the parameters (pulse length, laser fluence and
wavelength, particle size and shape, etc.) light absorption or an enhanced near field scattering can lead to perforation of
the cell membrane when the particle is in close vicinity. Here we present our experimental results to clarify the
perforation initiating mechanisms. The generation of cavitation and gas bubbles due to the laser induced effects were
observed via time resolved imaging. Additionally, pump-probe experiments for bubble detection was performed.
Furthermore, in our patch clamp studies a depolarization of the membrane potential and the current through the
membrane of AuNP loaded cell during laser treatment was detected. This indicates an exchange of extra- and intra
cellular ions trough the perforated cell membrane for some milliseconds. Additionally investigations by ESEM imaging
were applied to study the interaction of cells and AuNP after co incubation. The images show an attachment of AuNP at
the cell membrane after several hours of incubation. Moreover, images of irradiated and AuNP loaded cells were taken to
visualize the laser induced effects.