TITLE:
Laser Pulse Duration Optimization for Photothermal Therapy with Gold Nanostars
AUTHORS:
Juntao Cao
KEYWORDS:
Photothermal Therapy, Photothermal Imaging, Gold Nanostars, Laser Ablation
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.7 No.3,
August
24,
2018
ABSTRACT: Photothermal
therapy (PTT), which utilizes light radiation to create localized heating
effect in the targeted areas, is a promising solution for highly specific yet
minimally invasive cancer therapy. PTT uses photothermal agents, which are
usually nanoparticles that absorb strongly in the near-infrared optical window
where minimal tissue absorption occurs. Photothermal agents are also highly
functionalized to target at specific tumor sites. Gold nanostar is an ideal
candidate for photothermal agents, because it not only has a Surface Plasmon
Resonance in the near-infrared, but also can be easily produced and purified,
and is extremely versatile in the drug delivery process. In order to achieve
maximum amount of localized heating, pulse lasers are usually used in laser
ablation processes like photothermal therapy. However, intensive laser radiation
can cause damage to regular tissues as well the nanostructures themselves.
Therefore, identifying the optimal pulse duration to effectively generate localized
heating in the tumorous tissues while keeping the normal tissues and the
nanostructures intact is important to achieving optimal photo-therapeutic results.
This manuscript provides a numerical calculation method with Comsol
Multiphysics to optimize the pulse condition of the gold nanostars under photothermal
therapy settings. Based on results, gold nanostar displays significant
temperature heterogeneity under femtosecond and picosecond laser radiation,
while nanosecond laser only induces rather uniform heating effects across the
entire gold nanostar particle. This finding indicates that femtosecond laser,
which is the most common type of laser used for ablation, is likely to melt the
tip of the gold nanostar before the nanostar body reaches a reasonably high
temperature. Picosecond and nanosecond lasers are much less likely to induce
such dramatic morphology change. This study offers important insight into
finding the optimal condition for photothermal therapy with maximal efficacy
and minimal damage.