Optimization of ultrasound heating with Pickering droplets using core-shell scattering theory

Nanoparticles find widespread application in various medical contexts, including targeted nanomedicine and enhancing therapeutic efficacy. Moreover, they are employed to stabilize emulsions, giving rise to stabilized droplets known as Pickering droplets. Among the various methods to improve anti-cancer treatment, ultrasound hyperthermia stands out as an efficient approach. This research proposes Pickering droplets as promising sonosensitizer candidates, to enhance the attenuation of ultrasound with simultaneous potential to act as drug carriers. The enhanced ultrasound energy dissipation could be, therefore, optimized by changing the parameters of Pickering droplets. The ultrasound scattering theory, based on the core-shell model, was employed to calculate theoretical ultrasound properties such as attenuation and velocity. Additionally, computer simulations, based on a bioheat transfer model, were utilized to compute heat generation in agar-based phantoms of tissues under different ultrasound wave frequencies. Two types of phantoms were simulated: a pure agar phantom and an agar phantom incorporating spherical inclusions. The spherical inclusions, with a diameter of 10 mm, were doped with various sizes of Pickering droplets, considering their core radius and shell thickness. Computer simulation of these spherical inclusions incorporated within agar phantom resulted in different enhancement of achieved temperature elevation, which depending on the core radius, shell thickness, and the material properties of the system. Notably, spherical inclusions doped with Pickering droplets stabilized by magnetite nanoparticles exhibited a higher temperature rise compared to droplets stabilized by silica nanoparticles. Moreover, nanodroplets with a core radius below 400 nm demonstrated better heating performance compared to microdroplets. Furthermore, Pickering droplets incorporated into agar phantom could allow obtaining a similar effect of local heating as sophisticated focused ultrasound devices.