Theoretical and in vivo investigations of morphology and concentration of gold nanoparticles for laser surgery

Abstract Background and Objective Precise control of the thermal damage is critical during thermal therapy with the assistance of gold nanoparticles, which depends on the laser parameters and characteristics of gold nanoparticles. However, the current understanding of the relationship between the gold nanoparticles/incident laser light and the efficiency of photothermal therapy is limited, which should be studied systematically. Materials and Methods In this study, theoretical simulations were conducted to investigate the influence of laser wavelength, the size and shape of gold nanoparticles, and the distance of the particle in complex nanostructures on the optical properties and temperature distribution after laser irradiation, aiming to achieve maximum photothermal conversion efficiency and therapeutic effect during the laser treatment of port wine stains. Thereafter, gold nanoparticles were prepared and in vivo experiments were conducted to evaluate the effect on thermal damage of blood vessels. Results For the laser wavelength at 532 nm, gold nanospheres with diameters of 20 nm are ideal in terms of temperature rise. The optimized particle distance is 5 nm and the corresponding concentration is 0.26 mg/ml. For Nd:YAG laser at 1064 nm, gold nanorods with an aspect ratio of 6.3 and an effective radius of 12.7 nm are the most effective photothermal agents. The optimized particle distance is 4 nm, yielding the optimal concentration of 0.017 mg/ml. In vivo results demonstrated that using gold nanoparticles following our simulations as photothermal agents can greatly enhance the thermal damage of diseased blood vessels, reducing the laser energy and laser pulses required for the obvious thermal response of blood vessels. Conclusion For different laser wavelengths used in clinics in the near future, theoretical models presented in this study can be employed to obtain the morphology of single gold nanoparticle and the concentration of nanoparticles solutions, thereby obtaining the optimal photothermal conversion and enhanced thermal damage assisted by gold nanoparticles.