Photothermal therapy is gathering momentum. In order to assess the effects of the encapsulation of individual or clustered superparamagnetic iron oxide nanoparticles (SPIONs) on nanoparticle light-to-heat conversion, we designed and tested individual and clustered SPIONs encapsulated within a silica shell. Our study compared both photothermia and magnetic hyperthermia, and it involved individual SPIONs as well as silica-encapsulated individual and clustered SPIONs. While, as expected, SPION clustering reduced heat generation in magnetic hyperthermia, the silica shell improved SPION heating in photothermia.

Cancerous cells and the tumor microenvironment are among key elements involved in cancer development, progression, and resistance to treatment. In order to tackle the cells and the extracellular matrix, we herein propose the use of a class of silica-coated iron oxide nanochains, which have superior magnetic responsiveness and can act as efficient photothermal agents. When internalized by different cancer cell lines and normal (non-cancerous) cells, the nanochains are not toxic, as assessed on 2D and 3D cell culture models. Yet, upon irradiation with near infrared light, the nanochains become efficient cytotoxic photothermal agents. Besides, not only do they generate hyperthermia, which effectively eradicates tumor cells in vitro, but they also locally melt the collagen matrix, as we evidence in real-time, using engineered cell sheets with self-secreted extracellular matrix. By simultaneously acting as physical (magnetic and photothermal) effectors and chemical delivery systems, the nanochain-based platforms offer original multimodal possibilities for prospective cancer treatment, affecting both the cells and the extracellular matrix.