Menezes, Paula Cristina da Silva2026-01-082026-01-082025http://hdl.handle.net/10400.5/116529Tese de Mestrado, Engenharia Biomédica e Biofísica, 2025, Universidade de Lisboa, Faculdade de CiênciasGold nanoparticles (AuNPs) have attracted significant interest over the past two decades due to their unique optical and physicochemical properties, making them promising tools for biomedical applications, particularly photothermal therapy (PTT). Their ability to absorb electromagnetic radiation and convert it into heat through surface plasmon resonance (SPR) underlies their potential to selectively ablate tumor tissue while sparing surrounding healthy structures, provided that irradiation parameters are carefully optimized. However, the efficiency of AuNP-mediated PTT depends not only on nanoparticle properties but also on external factors, such as the irradiation wavelength, laser mode, suspension medium, and experimental model. This dissertation systematically investigated how these variables influence AuNP photothermal behavior with the aim of evaluating their translational potential for biomedical use. A range of experimental setups was employed, including cuvettes (liquid or agar-based), multiwell plates of varying geometries, and AuNPs suspended in different medium (Milli-Q water, PBS, and cell culture medium). Lasers of distinct wavelengths (520, 808, and 1064 nm) and laser modes (continuous vs. pulsed) were compared to assess their capacity to induce controlled heating under conditions relevant to PTT. Appropriate controls, including medium-only and black plasticine, validated the reproducibility and sensitivity of the setup. Findings confirmed that AuNP photothermal efficiency is strongly context dependent. Continuous-wave lasers enabled gradual and sustained hyperthermia, whereas pulsed lasers generated abrupt, localized heating with potential for nonlinear effects. Medium composition and experimental geometry also significantly modulated heat dissipation. Visible lasers were effective for superficial or in vitro applications, while near-infrared irradiation—particularly within the NIR-II window—emerged as the most promising approach for deeper tissue treatment. Overall, this study highlights the critical importance of systematically adapting irradiation conditions, experimental models, and nanoparticle environments to optimize PTT outcomes and bring AuNP-based therapies closer to clinical translation.application/pdfengGold nanoparticlesPhotothermal therapyNear-infraredLaser irradiationNanomedicinemaster thesis204175720