Gold Nanoparticles as a Photothermal Agent in Cancer Therapy: The Thermal Ablation Characteristic Length

Abstract

In cancer therapy, the thermal ablation of diseased cells by embedded nanoparticles is one of the known therapies. It is based on the absorption of the energy of the illuminating laser by nanoparticles. The resulting heating of nanoparticles kills the cell where these photothermal agents are embedded. One of the main constraints of this therapy is preserving the surrounding healthy cells. Therefore, two parameters are of interest. The first one is the thermal ablation characteristic length, which corresponds to an action distance around the nanoparticles for which the temperature exceeds the ablation threshold. This critical geometric parameter is related to the expected conservation of the body temperature in the surroundings of the diseased cell. The second parameter is the temperature that should be reached to achieve active thermal agents. The temperature depends on the power of the illuminating laser, on the size of nanoparticles and on their physical properties. The purpose of this paper is to propose behavior laws under the constraints of both the body temperature at the boundary of the cell to preserve surrounding cells and an acceptable range of temperature in the target cell. The behavior laws are deduced from the finite element method, which is able to model aggregates of nanoparticles. We deduce sensitivities to the laser power and to the particle size. We show that the tuning of the temperature elevation and of the distance of action of a single nanoparticle is not significantly affected by variations of the particle size and of the laser power. Aggregates of nanoparticles are much more efficient, but represent a potential risk to the surrounding cells. Fortunately, by tuning the laser power, the thermal ablation characteristic length can be controlled.

Liposomal IR-780 as a Highly Stable Nanotheranostic Agent for Improved Photothermal/Photodynamic Therapy of Brain Tumors by Convection-Enhanced Delivery

“…One of major concerns of PTT is the drainage of generated heat into the tumor vicinity, which could lead to unintended damage to neighboring non-tumor cells [4]. This difficulty could be overcome by using a PA for locally induced heat generation upon NIR light irradiation, where selective cancer cell killing occurs only after the intracellular uptake of the PA [5]. Other than ICG, many inorganic nanomaterials such as magnetic nanoparticles, Au nanorods and carbon-based nanomaterials are good PAs [6].…”

Gold as a Possible Alternative to Platinum-Based Chemotherapy for Colon Cancer Treatment

“…Moreover, near-infrared light can safely and deeply trespass healthy tissue and reach the tumor-embedded photothermal agents. By modifying the size and shape of GNPs, their optical properties can be controlled to maximize the absorption of near-infrared light, thus allowing their application in the novel and safer PTT approach [160,162,163]. Furthermore, the tunable size and shape of GNPs is related to a higher photothermal conversion efficiency [162,164].…”

Synthesis and In Vitro Evaluation of Gold Nanoparticles Functionalized with Thiol Ligands for Robust Radiolabeling with 99mTc

“…A multifunctional radiopharmaceutical, such as the one described herein, ([ 99m Tc]Tc-AuNP may function simultaneously as both a radiodiagnostic imaging agent and a thermal ablation system (i.e., localized heating after laser irradiation) in cancer cells [26,27]. The aim of this initial research study was to functionalize the surfaces of AuNPs of two different sizes (2 nm and 20 nm, referred to as Au (2) NPs and Au (20) NPs, respectively), with two thiol ligands (referred to as L 1 H and L 2 H), which allow direct labeling with 99m Tc-carbonyls.…”