Ferrnando López Arbeloa

Nanosystems that simultaneously contain fluorescent and magnetic modules can offer decisive advantages in the development of new biomedical approaches. A biomaterial that enables multimodal imaging and contains highly efficient nanoheaters together with an intrinsic temperature sensor would become an archetypical theranostic agent. In this work, we have designed a magneto-luminescent system based on Fe₃O₄ NPs with large heating power and thermosensitive rhodamine (Rh) fluorophores that exhibits the ability to self-monitor the hyperthermia degree. Three samples composed of highly homogeneous Fe₃O₄ NPs of ∼25 nm and different morphologies (cuboctahedrons, octahedrons, and irregular truncated-octahedrons) have been finely synthesized. These NPs have been thoroughly studied in order to choose the most efficient inorganic core for magnetic hyperthermia under clinically safe radiofrequency. Surface functionalization of selected Fe₃O₄ NPs has been carried out using fluorescent copolymers composed of PMAO, PEG and Rh. Copolymers with distinct PEG tail lengths (5-20 kDa) and different Rh percentages (5, 10, and 25%) have been synthesized, finding out that the copolymer with 20 kDa PEG and 10% Rh provides the best coating for an efficient fluorescence with minimal aggregation effects. The optimized Fe₃O₄@Rh system offers very suitable fluorescence thermosensitivity in the therapeutic hyperthermia range. Additionally, this sample presents good biocompatibility and displays an excellent heating capacity within the clinical safety limits of the AC field (≈ 1000 W/g at 142 kHz and 44 mT), which has been confirmed by both calorimetry and AC magnetometry. Thus, the current work opens up promising avenues toward next-generation medical technologies.

New organophosphonate derivatives of monovacant Keggin-type polyoxotungstates that contain naphthyl groups have been synthesized and characterized in both solid state and solution. Single-crystal structural analysis shows that two phosphonate groups occupy the vacant position of the lacunary cluster unit in the isostructural compounds [N(C₄H₉)₄]₃[H(POC₁₁H₉)₂(α-HBW₁₁O₃₉)] (TBA-1) and [N(C₄H₉)₄]₃[H(POC₁₁H₉)₂(α-SiW₁₁O₃₉)] (TBA-2). Liquid-solution UV–Vis transmittance and solid-state diffuse reflectance spectroscopy studies reveal the presence of a new absorption band in the visible region, the charge transfer character of which has been further confirmed by time-dependent density functional theory (TD-DFT) calculations. The latter evidence that the charge transfer process is dominated by transitions from the highest occupied molecular orbital (HOMO), localized in the aromatic ring of the organic group, to the lowest unoccupied molecular orbital (LUMO), localized in the Keggin anion. Photoluminescence studies show that the fluorescent properties of the 1-naphthylmethylphosphonate group are quenched upon its incorporation into the inorganic oxo-tungstate skeleton. The solution stability of the hybrid clusters has been evaluated by a combination of ¹H-, ¹³C- and ³¹P-Nuclear Magnetic Resonance spectroscopy and Electrospray Ionization-Mass Spectrometry. The hybrid polyanion [H(POC₁₁H₉)₂(α-HBW₁₁O₃₉)]³⁻ (1) herein constitutes the first structurally characterized organo-p-block containing borotungstate, and hence it confirms that this strategy for the organic functionalization of polyoxometalate clusters can be applied to new platforms belonging to the family of group-13 heteropolyoxotungstates.

In the AlPO ₄ system, 1,2,3-trimethylimidazolium fails to produce 5-membered rings (as expected) but did not produce double-4-membered ring structures either.