Development of rare earth tantalates doped with lanthanide ions for multimodal bioimaging and nanothermometry

• Ano de defesa: 2025
• Autor(a) principal: Ribeiro, Fernanda Hediger Borges
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Biofotônica; Biophotonics; Controle morfológico; Imageamento multimodal; Luminescence; Luminescência; Morphological control; Multimodal imaging; Nanotermometria; Nanothermometry; Rare earths; Terras raras
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/59/59138/tde-30092025-094844/

In the medical field, bioimaging has emerged as a powerful non-contact diagnostic tool, including a diverse array of imaging modalities, such as optical (OI), magnetic resonance (MR), computed tomography (CT), photoacoustic (PA), among others. These techniques provide different advantages and valuable information to biological systems and enabling advancements in both research and clinical diagnostics. To address the growing demand for more efficient and reliable image detection, multimodal imaging is an approach that combines different imaging modalities, benefiting from their respective advantages. In this context, the challenge is to develop a single material that has good contrast capabilities in the across different techniques. For that, Gd3+ -based materials have been extensively explored due to the seven unpaired electron configuration (4f7 ) of Gd3+ and its high atomic number (Z = 64), which endows it with excellent paramagnetic properties and X-ray absorption capabilities. Also, Ta possesses a high atomic number (Z=73), which gives it a strong X-ray attenuation property, making it an excellent contrast agent (CA) for CT as well. For these reasons, tantalum- and gadoliniumbased materials (tantalum oxide and rare earth (RE) tantalates) have been identified as suitable candidates for study in this application The synthetic route plays an important role in the morphology and size of the particles. Although the number of publications on these materials has grown, most of these studies have not reported on the morphology and size control of these compounds. Here, we proposed novel synthesis for Ta2O5 and RE tantalates (RE3TaO7 and RETaO4) (undoped and doped with Ln3+ ions, Ln=Eu, Er, Yb, Tm, Nd) with structural, morphological, and size control using ethylene glycol as a solvent. First, we bring the synthesis optimization and the material characterization of Er3+/Yb3+ co-doped Ta2O5, where we study the influence of the annealing temperature and of the Yb3+ ions concentration. Their thermometric properties were also investigated based on Boltzmann distribution law, from the ratio of 2H11/2 → 4 I15/2 and 4S3/2 → 4 I15/2 transitions of Er3+ ions. Second, the control of the size and morphology of these RE3TaO7 materials was achieved via polyol-mediated method, paving the way to their use in several biomedical applications. Considering the factors such as high atomic number, high density, and the optical properties of Gd3TaO7, these tantalates emerge as strong and promising candidates as a multimodal imaging probe. Therefore, the focus was to investigate their properties and evaluate the feasibility of the application of these materials as CAs in different imaging techniques (MR, CT, and OI, including time-gated luminescence - TGL). Next, we show the synthesis of RE tantalate nanoparticles (RE3TaO7, for RE=Y, Dy, and Gd), achieving ~40 nm spherical particles. The formation of pure cubic phases and their potential for multimodal imaging are explored. Special attention is given to the challenges of phase control in gadolinium tantalates. Finally, the pure phase M\'-GdTaO4 nanoparticles was obtained, overcoming the challenges of phase separation through optimization of precursor ratios. These particles exhibited promising scintillating properties, with perspectives for X-ray photodynamic therapy (X-PDT).