Nanoparticle concentration dependence of photothermal therapy of cancer

Photothermal therapy (PTT) of cancer and bacterial infections is an emerging field that benefits from the light-matter interactions of targeted nanoparticles. Low concentrations of these nanoparticles are desired for low toxicity and low laser excitation power is desired for minimizing proximal tissue damage. Despite earlier experimental success in the PTT with hybrid nanoparticles, a fundamental understanding of concentration-dependence of the photothermal effect is missing. Hence, a computational/theoretical approach must account for the strength of the experimental photothermal effect. Here, we used electromagnetic FDTD simulations and effective medium theory to accurately estimate the in vitro heating behavior of PAA-SPION nanoparticles in water for 640 nm excitation. These nanoparticles were demonstrated to be highly effective in selective killing of prostate cancer cells under near-infrared irradiation (Biomater. Sci., 10, 3951 (2022)). FDTD Solver and EMT using Stack Solver were used to solve for the nanoparticle concentration dependence of their absorption within 450-1000 nm. Our results might pave the way for low-concentration, low power, targeted and drug-loaded PTT.