Optomagnetic Nanoplatforms for In Situ Controlled Hyperthermia

Magnetic nanoparticles (M:NPs) are unique agents for in vivo thermal therapies due to their multimodal capacity for efficient heat generation under optical and/or magnetic excitation. Nevertheless, their transfer from laboratory to the clinic is hampered by the absence of thermal feedback and by the influence that external conditions (e.g., agglomeration and biological matrix interactions) have on their heating efficiency. Overcoming these limitations requires, first, the implementation of strategies providing thermal sensing to M:NPs in order to obtain in situ thermal feedback during thermal therapies. At the same time, M:NPs should be modified so that their heating efficiency will be maintained independently of the environment and the added capability for thermometry. In this work, optomagnetic hybrid nanostructures (OMHSs) that simultaneously satisfy these two conditions are presented. Polymeric encapsulation of M:NPs with neodymium‐doped nanoparticles results in a hybrid structure capable of subtissue thermal feedback while making the heating efficiency of M:NPs independent of the medium. The potential application of the OMHSs herein developed for fully controlled thermal therapies is demonstrated by an ex vivo endoscope‐assisted controlled intracoronary heating experiment.     

KCI： Eu^2＋ as a solar UV-C radiation dosimeter. Optically stimulated luminescence and thermoluminescence analyses

The KCl:Eu²⁺ system response to UV-C was investigated by analyzing the optically stimulated luminescence (OSL) and thermo-luminescence (TL) signal produced by ultraviolet light exposure at room temperature. It was found that after UV-C irradiation, OSL was produced on a wide band of visible wavelengths with decay time that varied by several orders of magnitude depending on the Eu²⁺ aggregation state. In spite of the low intensity of solar UV-C reaching the Earth's surface in Madrid (40º N, 700 m a.s.l.), it was possible to measure the UV-C radiation dose at 6:48 solar time by using the TL response of the KCl:Eu²⁺ system and differentiate it from the ambient beta radiation dose.     

Unveiling Molecular Changes in Water by Small Luminescent Nanoparticles

Nowadays a large variety of applications are based on solid nanoparticles dispersed in liquids—so called nanofluids. The interaction between the fluid and the nanoparticles plays a decisive role in the physical properties of the nanofluid. A novel approach based on the nonradiative energy transfer between two small luminescent nanocrystals (GdVO₄:Nd³⁺ and GdVO₄:Yb³⁺) dispersed in water is used in this work to investigate how temperature affects both the processes of interaction between nanoparticles and the effect of the fluid on the nanoparticles. From a systematic analysis of the effect of temperature on the GdVO₄:Nd³⁺ → GdVO₄:Yb³⁺ interparticle energy transfer, it can be concluded that a dramatic increase in the energy transfer efficiency occurs for temperatures above 45 °C. This change is properly explained by taking into account a crossover existing in diverse water properties that occurs at about this temperature. The obtained results allow elucidation on the molecular arrangement of water molecules below and above this crossover temperature. In addition, it is observed that an energy transfer process is produced as a result of interparticle collisions that induce irreversible ion exchange between the interacting nanoparticles.     

Ag/Ag2S Nanocrystals for High Sensitivity Near‐Infrared Luminescence Nanothermometry

Temperature sensing in biological media (cells, tissues, and living organisms) has become essential in the development of the last generation of diagnostics and therapeutic strategies. Thermometry can be used for early detection of different diseases, such as cancer, stroke, or inflammation processes, one of whose incipient symptoms is the appearance of localized temperature singularities. Luminescence nanothermometry, as a tool to accurately provide temperature sensing in biological media, requires the rational design and development of nanothermometers operating in the second biological window. In this work, this is achieved using Ag/Ag₂S nanocrystals as multiparametric thermal sensing probes. Temperature sensing with remarkably high sensitivity (4% °C^?1) is possible through intensity‐based measurements, as their infrared emission is strongly quenched by small temperature variations within the biological range (15–50 °C). Heating also results in a remarkable redshift of the emission band, which allows for concentration‐independent temperature sensing based on infrared ratiometric measurements, with thermal sensitivity close to 2% °C^?1. These results make Ag/Ag₂S nanocrystals the most sensitive among all noncomposite nanothermometers operating in the second biological window reported so far, allowing for deep‐tissue temperature measurements with low uncertainty (0.2 °C).     

Red and green fluorescence of Mn in NaCl

The fluorescence (emission and excitation) spectrum of Mn²⁺ ion in NaCl has been investigated for freshly quenched samples (diluted Mn²⁺ ions) and as grown samples (Mn²⁺ ions forming aggregates and/or precipitates). Two main emission bands are generally observed in as grown samples, peaking at 505 nm and around 610 nm. Both emission bands are related to different manganese precipitates. Quenched samples show only the red emission but peaking at 605 nm and with a different excitation spectrum to that of the as grown crystals. Thus, this crystal is suitable to operate as a double color (red and green) emitting phosphor where the red and green relative intensities can be controlled by a thermal treatment.     

Infrared fluorescence imaging of infarcted hearts with Ag2S nanodots

Ag₂S nanodots have already been demonstrated as promising near-infrared (NIR-II, 1.0–1.45 μm) emitting nanoprobes with low toxicity, high penetration and high resolution for in vivo imaging of, for example, tumors and vasculature. In this work, we have systematically investigated the potential application of functionalized Ag₂S nanodots for accurate imaging of damaged myocardium tissues after a myocardial infarction induced by either partial or global ischemia. Ag₂S nanodots surface-functionalized with the angiotensin II peptide (ATII) have shown over 10-fold enhanced binding efficiency to damaged tissues than non-specifically (PEG) functionalized Ag₂S nanodots due to their interaction with the upregulated angiotensin II receptor type I (AT1R). It is demonstrated how the NIR-II images generated by ATII-functionalized Ag₂S nanodots contain valuable information about the location and extension of damaged tissue in the myocardium allowing for a proper identification of the occluded artery as well as an indirect evaluation of the damage level. The potential application of Ag₂S nanodots in the near future for in vivo imaging of myocardial infarction was also corroborated by performing proof of concept whole body imaging experiments.

     

Optical effects caused by high laser powers in ion-implanted Bi4Ge3O12 waveguides

Abstract

The ‘optical writing’ of permanent channel waveguides in the surface of He⁺ ion-implanted bismuth germanate, Bi₄Ge₃O₁₂, has been studied, using end-coupled argon and Ti:sapphire CW laser beams. Comparisons of the self-focusing effect in waveguides and bulk samples have been made for both Nd³⁺ doped and undoped material. The permanent ‘writing’ effect has been compared with the structural change observed earlier in ion-implanted Bi₄Ge₃O₁₂ waveguides annealed at high temperature.