Boosting Light Absorption of a Therapeutic Microcapsule by Means of Auxiliary Solid Nanoparticles

Abstract: Multilayer microparticles with a liquid core and a polycomposite light-absorbing shell are important components of modern bio- and medical technologies, in particular, as transport microcontainers in the system of targeted delivery of therapeutic nanodoses to the desired region of the biological tissues. For reliably opening the microcapsule shell by an optical radiation and releasing the payload, it is necessary to dramatically increase the light absorption of such a microcontainer. To this end, we propose surrounding the microcapsule with specially added auxiliary nanoparticles, which can accumulate optical energy near its surface and direct a concentrated photonic flux to the target microcapsule thus leading to its booster heating. Using numerical finite-difference time-domain (FDTD) calculations, we simulate and examine the absorption dynamics of the near-infrared optical radiation in a spherical microcapsule surrounded by solid nanoparticles of different optical properties (metal, biocompatible dielectric). We show that due to light scattering on nanoparticles, the optical field superlocalization in the "hot regions" on the microcapsule surface occurs. The three-fold light absorption enhancement can be achieved due to the addition of nanoparticles.