Therapy with Gold Nanoparticles and Lasers: What Really Kills The Cells?

Abstract

Two articles were published recently in Nanomedicine: “Enhanced imaging and acceler‐ ated photothermalysis of A549 human lung can‐ cer cells by gold nanospheres” by Liu et al. [1] and “LANTCET: elimination of solid tumor cells with photothermal bubbles generated around clusters of gold nanoparticles” by Hleb et al. [2]. These two articles were published simultaneously and share many similarities: they aim to use gold nanopar‐ ticles (GNPs) and laser radiation for the detec‐ tion and destruction of cancer cells, they use the same model cells (A549) and nanoparticles (gold spheres), and similar in vitro incubation methods of the cells with GNP and similar continuous 633‐nm laser radiation is used. Reported results are also comparable: cell damage was observed after GNP and laser treatment. However, closer examination and comparison of these two studies has yielded several significant differences in the experimental methods, models and interpretation of the results. We have presented some of these differences in Table 1 assuming that the same cells and the same GNP were studied. The key idea of photothermal therapy is that GNPs locally convert optical energy into ther‐ mal energy through their unique mechanism of plasmon resonance. This idea is the basis behind all published work on GNP‐based photothermal methods. The two articles under consideration report almost opposite approaches and results in using 633‐nm laser radiation: Liu et al. [1] employs 633 nm c.w. radiation for inducing NP‐mediated damage to the cells, while Hleb et al. [2] uses the same radiation (with possibly lower power) for noninvasive optical monitoring of the same cells and employs different wavelengths of laser radia‐ tion (532 nm) for inducing NP‐mediated dam‐ age to the cells. We later discuss this apparent contradiction hoping that such discussion may be helpful to the Nanomedicine readership for understanding and optimizing the GNP‐based diagnostic and therapeutic methods. Experimental approach & results by Lui et al. Gold nanoparticles are suggested for cancer opti‐ cal diagnostics and treatment for their excellent scattering and photothermal properties. Lung can‐ cer cells (A549) were incubated with 40‐nm gold spheres conjugated with IgG and were then treated with 633‐nm continuous laser radiation. Cell viability was monitored through laser‐induced fluorescence of a standard violet dye. The authors have already recently published approximately 20 papers related to the synthesis, modifications and biomedical applications of GNPs.