This chapter focuses on two key areas of research in biomedical applications: the synthesis and characterization of spherical silicon dioxide nanostructures and the development of magnetic ferrite (Fe3O4) nanocomposites coated with SiO2. First, the synthesis process of silica nanospheres is described in detail, highlighting their compact and porous structure using conventional Stöber and modified Stöber methods. Structural characterization includes techniques such as, X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), while the measurement of thermal properties reveals data relevant to biomedical applications using the thermal wave resonant cavity (TWRC) technique. Second, the synthesis of Fe3O4 nanoparticles with magnetic properties and their encapsulation into a SiO2 layer, allowing the loading of therapeutic agents, is addressed. This synthesis was characterized with the same techniques previously described for the nanocomposites, adding photothermal characterization, which help to evaluate their capacity to generate targeted heat, which is crucial in hyperthermia therapies, and to regulate the release of therapeutic agents. Finally, the results obtained are discussed, highlighting the viability and potential of these materials in biomedical and therapeutic applications, as well as the importance of structural and thermal characterization in their development. The performance of the TWRC method for nanofluid thermal analysis is emphasized, as its accuracy and reliability were supported by benchmarking the obtained results against reference values reported in the literature. Overall, this chapter provides an integrated perspective on recent progress in nanomaterials for biomedical applications and identifies several promising directions for future work in this area.