Lanthanide-activated fluoride-based nanostructures are extremely interesting multifunctional tools for many modern applications in nanomedicine, e.g., bioimaging, sensing, drug delivery, and photodynamic therapy. Importantly, environmental-friendly preparations using a green chemistry approach, as hydrothermal synthesis route, are nowadays highly desirable to obtain colloidal nanoparticles, directly dispersible in hydrophilic media, as physiological solution. The nanomaterials under investigation are new KY₃F₁₀-based citrate-capped core@shell nanostructures activated with several lanthanide ions, namely, Er³⁺, Yb³⁺, Nd³⁺, and Gd³⁺, prepared as colloidal water dispersions. A new facile microwave-assisted synthesis has been exploited for their preparation, with significant reduction of the reaction times and a fine control of the nanoparticle size. These core@shell multifunctional architectures have been investigated for use as biocompatible and efficient contrast agents for optical, magnetic resonance imaging (MRI) and computerized tomography (CT) techniques. These multifunctional nanostructures are also efficient noninvasive optical nanothermometers. In fact, the lanthanide emission intensities have shown a relevant relative variation as a function of the temperature, in the visible and near-infrared optical ranges, efficiently exploiting ratiometric intensity methods for optical thermometry. Importantly, in contrast with other fluoride hosts, chemical dissolution of KY₃F₁₀ citrate-capped nanocrystals in aqueous environment is very limited, of paramount importance for applications in biological fluids. Furthermore, due to the strong paramagnetic properties of lanthanides (e.g., Gd³⁺), and X-ray absorption of both yttrium and lanthanides, the nanostructures under investigation are extremely useful for MRI and CT imaging. Biocompatibility studies of the nanomaterials have revealed very low cytotoxicity in dfferent human cell lines. All these features point to a successful use of these fluoride-based core@shell nanoarchitectures for simultaneous diagnostics and temperature sensing, ensuring an excellent biocompatibility.

This paper reports a comprehensive investigation of a magnetic nanoparticle (MNP), named M55, which belongs to a class of innovative doped ferrite nanomaterials, characterized by a self-limiting temperature. M55 is obtained from M48, an MNP previously described by our group, by implementing an additional purification step in the synthesis. M55, after citrate and glucose coating, is named G-M55. The present study aimed to demonstrate the properties of G-M55 as a diagnostic contrast agent for MRI and magnetic particle imaging (MPI), and as an antitumoral agent in magnetic fluid hyperthermia (MFH). Similar specific absorption rate values were obtained by standard MFH and by an MPI apparatus. This result is of interest in relation to the application of localized MFH by MPI apparatus. We demonstrated the biocompatibility of G-M55 in a triple-negative human breast cancer line (MDA-MB-231), and its efficacy as an MFH agent in the same cell line. We also demonstrated the efficacy of MFH treatment with G-M55 in an experimental model of breast cancer. Overall, our results pave the way for the clinical application of G-M55 as an MFH agent in breast cancer therapy, allowing not only efficient treatment by both standard MFH apparatus and MPI but also temperature monitoring.

Purpose: This study investigates the theranostic potential of doped ferrite nanoparticles (NPs) with self-regulating temperature (SRT) properties, termed M55, coated with glucose (GM55), chitosan (CM55), and poly-ethylene glycol (PM55). The NPs were assessed for their physicochemical attributes, magnetic fluid hyperthermia (MFH) efficacy, dual-imaging capabilities in Magnetic Resonance Imaging (MRI) and Magnetic Particle Imaging (MPI), cytocompatibility, and cellular uptake. Methods: Physicochemical characterization was conducted using Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and zeta potential measurements. The biocompatibility and cellular uptake were evaluated in MDA-MB-231 breast cancer cells, and MFH performance was tested in vitro. Following intravenous administration, MRI and MPI functionalities were analyzed through phantom studies and in vivo murine models. Results: Coated M55 NPs displayed high colloidal stability in water and effective functionalization. The specific absorption rate (SAR) of 24.4 ± 1.4 W/g confirmed their suitability for MFH applications. In vitro assays indicated excellent biocompatibility and substantial cellular internalization, with GM55 showing the highest uptake and MFH efficiency, reducing cell viability to 50.62 ± 3.92% post two treatment cycles, compared to 67.71 ± 6.11% (CM55) and 71.39 ± 5.84% (PM55). MRI transverse relaxivity (r₂) values were notably high across all coatings, enhancing imaging contrast. MPI analysis demonstrated superior cell labeling sensitivity, with GM55 achieving the most pronounced detection. In vivo imaging confirmed effective NPs accumulation in the liver, underscoring their utility as dual MRI/MPI contrast agents (CAs). Conclusion: Coated M55 NPs exhibit significant promise as multifunctional theranostic agents for cancer treatment. GM55, in particular, offers superior MFH efficacy and cellular uptake, while CM55 and PM55 may present unique advantages for alternative biomedical applications. The dual-imaging capabilities of these NPs provide a robust platform for real-time monitoring of distribution and therapeutic outcomes. Future investigations will focus on optimizing NPs formulations and expanding in vivo assessments to advance clinical translation.

Metal–organic chemical vapor deposition has been applied to produce europium-doped BaF ₂ thin films on silicon and quartz substrates. A combined experimental and theoretical study has proved the downshifting properties of the film.

In the present work, an in-depth study on the sol-gel process for the fabrication of Eu-doped CaF₂ materials in the form of thin films has been addressed for the production of down-shifting layers. Fine-tuning of the operative parameters, such as the annealing temperature, substrate nature and doping ion percentage, has been finalized in order to obtain Eu(III)-doped CaF₂ thin films via a reproducible and selective solution process for down-shifting applications. An accurate balance of such parameters allows for obtaining films with high uniformity in terms of both their structural and compositional features. The starting point of the synthesis is the use of a mixture of Ca(hfa)₂•diglyme•H₂O and Eu(hfa)₃•diglyme adducts, with a suited ratio to produce 5%, 10% and 15% Eu-doped CaF₂ films, in a water/ethanol solution. A full investigation of the structural, morphological and compositional features of the films, inspected using X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX), respectively, has stated a correlation between the annealing temperature and the structural characteristics and morphology of the CaF₂ thin films. Interestingly, crystalline CaF₂ films are obtained at quite low temperatures of 350–400 °C. The down-shifting properties, validated by taking luminescence measurements under UV excitation, have allowed us to correlate the local environment in terms of the degree of symmetry around the europium ions with the relative doping ion percentages.