Monitoring Photothermally Excited Nanoparticles via Multimodal Microscopy

Generation of heat using optically excited nanoparticles can be beneficial or detrimental depending on the application. Therefore, clinically applicable studies are being pursued in an effort to identify safe practices of nanoparticle-induced hyperthermia for the treatment of cancerous tissues using optical radiation. The imaging and characterization of localized heat production resulting from optically excited nanoparticles on both cellular and tissue levels is important for determination of nanoparticle dosage and optimal conditions for the radiation. In this report, we present a multimodal imaging method to monitor the local temperature change induced by photothermally excited, biologically relevant gold nanoshell clusters on the micrometer scale using two types of temperature-sensitive fluorescent reporters: Indo-1 or semiconductor quantum dots. The photoinduced heat flux from gold nanoshells is observed to be dependent on the dynamic motion of nanoparticles in the induced thermal gradient, with phenomena such as nanoparticle focusing strongly influencing the local temperature elevation.