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.
Highlights
In the last few decades, photothermal measurement techniques and applications to photothermal therapy (PTT) have been experiencing significant developments [1,2]
The parameters of Equations (1)–(4) for the electromagnetic and thermic problems are given in Table 1 [24]
To characterize the temperature elevation that is induced by illumination, we study both the influence of the laser power and of the volume of the nanoparticle
Summary
In the last few decades, photothermal measurement techniques and applications to photothermal therapy (PTT) have been experiencing significant developments [1,2]. Using near-infrared laser nanoabsorbers to generate a local heat source, inducing thermal ablation of cancer cells, has opened a new therapeutic area that provides more specificity and preserves surrounding tissues [3,4,5]. Such therapies are non-invasive, as they do not require surgery. Thermal ablation involves the delivery of nanoparticles by injection and illumination by using a laser to produce local heating, which destroys the tumoral cell [6,7,8,9,10]. The resulting temperature elevation depends on the geometrical and Molecules 2018, 23, 1316; doi:10.3390/molecules23061316 www.mdpi.com/journal/molecules
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