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Resumen del trabajo presentado a la NanoSpain Conference, celbrado en Logroño del 15 al 18 de marzo de 2016.

Resumen del trabajo presentado a la 11th International Conference on the Scientific and Clinical Applications of Magnetics Carriers, celebrada en Vancouver (Canada) del 31 de mayo al 4 de junio de 2016.-- et al., Magnetic hyperthemia has already been approved for therapy of cancer and other diseases. The treatment involves a direct injection of nanoparticles into the tumor and the application of an alternating magnetic field until temperature at the borders of the tumor is reaching 43 °C. As the heating power of magnetic nanoparticles is moderate, the amount nanoparticles to be injected for this purpose is very high and that means a long process until the nanoparticles are cleared from the body. On the other hand cell experiments indicate that cell dead can be produced without are increase of the cell temperature. This is suggesting that the development of local intracellular hyperthermia involving a smaller number of particles would be very possible. In order to make this strategy effective an adequate monitoring of the nanoheaters local temperature will be required. In order to investigate this pint we have developed a magnetic nanoplafform that incorporates a luminescent molecular thermometer. The thermometer is based on the luminescence emission of two lanthanide complexes with organic ligands that are located on the surface of the magnetic nucleus and in the interior of the hydrophobic part of an amphiphilic copolymer. One of the lanthanides emits with a constant intensity while the intensity of emission of the other decreases with the temperature, thus the ratio of emission intensities gives the absolute temperature on the surface of the nanoparticle beater. The thermometer shows a line sensitive (5.8%K at 296 K), low uncertainly (0.5K), high reproducibility (>99.5%), and fast time magnetic field reveal the existence of an important temperature gradient between nanoheaters and irreversible intracellular damage in tumor cells leading to cell death without having to increase the temperature of the whole tumor mass. A proof of concept of temperature mapping has been realized on cells that were incubated with the nanoparticles.

Resumen del trabajo presentado a la 15th International Conference on Molecule-Based Magnets, celebrada en Sendai (Japón) del 4 al 8 de septiembre de 2016., As nanotechnology progresses, new demands and new challenges arise. lndeed, the increased interest on hyperthermia therapies in nanomedicine has opened the need for an accurate control of heat transfer and heat release by a precise monitoring of the temperature. A straightforward solution to this demand would be the development of efficient and sensitive nanoparticles embedding both heaters and thermometers, something that despite intense activity in the recent years had resisted scientific efforts. Here we report the development of such device: a nanoplatforrn consisting in a magnetic nanoparticle incorporating a molecular thermometer just on the surface of the heater, thus having an unprecedented thermal contact and a quasi-instantaneous onset of temperature gradient from the heater to the medium. The heater/thermometer nanoplatform was prepared from iron oxide cores functionalized with Eu3+ and Tb3+ complexes, coated with a P4VP-b-P(PMEGAco-PEGA) copolymer and dispersed in water to obtain an aqueous ferrofluid suspension. The thermometric response results from thermally activated energy transfer between Eu3+- and Tb3+-emitting levels and triplet energy states of the ligands and of the host matrix. The beads thermometric performance is evaluated using the relative sensitivity Sr= (::/T)/:: which ranges from 0.5 to 5.8%/K, 295-315 K (maximum sensitivity of 5.8%/K at 296 K). Upon 10 consecutive temperature cycles between 297 and 310 K, the therrnometer reproducibility is 99.5%,. The time fluctuations of the therrnometric parameter :: are always below O. 7%. The uncertainty of the temperature measurement is 0.5 K. The heater/thermometer nanoplatforrn is applied to monitor local temperature changes under ac magnetic fields. A semiconductor thermometer immersed in the ferrofluid and an infrared camera focused on the container wall were used for comparative purposes. A multiple-pulse protocol is illustrated in the Figure showing differences between the fast and direct temperature reading of the molecular thermometer and those from the (indirect) semiconductor and IR ones. Such differences are related to heat flow at the nanoscale and could not be observed before using more conventional systems. In addition, we show here the temperature mapping near the nucleus of Opossum kidney cells incubated with the nanoparticles.

Understanding the influence of dipolar interactions in magnetic hyperthermia (MH) experiments is of crucial importance for a fine optimization of nanoparticle (NP) heating power. In this study, we use a kinetic Monte-Carlo algorithm to calculate hysteresis loops, so both time and temperature are correctly taken into account. It is demonstrated that this algorithm correctly reproduces the high-frequency hysteresis loop of both superparamagnetic NPs and ferromagnetic ones without any ad-hoc parameters. The algorithm is easily parallelizable so calculation on several processors decreases considerably calculation time. The specific absorption rate (SAR) of NPs dispersed inside spherical lysosomes is studied as a function of several key parameters: volume concentration, applied magnetic field, lysosome size, NP diameter and anisotropy. The influence of these parameters is illustrated and comprehensively explained. In summary, the effect of magnetic interactions is to increase the coercive field, saturation field and hysteresis area of major loops. However, for small amplitude magnetic field such as the ones used in MH, the heating power as function of concentration can increase, decrease or display a bell shape, depending of the relationship between the applied magnetic field and the coercive/saturation fields of the NPs. The hysteresis area is found to be well correlated to the parallel or antiparallel nature of the dipolar field acting on each NP. It is shown that the heating power increases or decreases sharply in the vicinity of the lysosome membrane. The amplitude of variation reaches more than one order of magnitude in certain conditions. Finally, implications of these various findings are discussed in the framework of MH optimization. It is concluded that feedbacks on specific points from biology experiments are required for further advance on the optimization of NPs for MH., 25 pages, 11 figures

Resumen del trabajo presentado a la "2nd European Event in Nanoscience & Nanotechnology" celebrado en Bilbao (España) del 23 al 26 de abril de 2013., Working machinery in life is nanometric, thus, it is no wonder tliat the development of adequate nanotools would be very helpful in biomedical science. In this direction, the idea behind this work is to build a nanoplatform that can incorporate, in an easy way, multiple physical and biological functionalities. The core of the platform is an hydrophobic polymer that may be used as a matrix for the encapsulation of inorganic nanoparticles (magnetic, luminescent, radioactive, . . .). This matrix contains a Michael acceptor (or an acceptor) on its surface for functionalization. Organic bioactive molecules are attached to one end of a hydrophilic polymer (Le. PEG) terminated on a Michael acceptor (or a donor), and then they are anchored to the hydrophobic core by Michael addition. This system has the advantages of a clean synthesis (no by-products), mild conditions, and an easy and controlled multifunctionalization. The nanoplatform has been functionalized with radiochemical tracers (In111), luminescent dyes (fluorescein, rhodamine, lanthanide compounds), and magnetic nanoparticles, and therefore it can be a powerful tool in imaging. Besides, it has also been functionalized with a therapeutical drug, an antibody, and an optical thermometer made of lanthanide complexes. Health safety of tlhe system has been tested in cellular and in vivo assays. The nanoplatform is highly stable in biological fluids, shows low cell toxicity, high capacity of cell internalization, excellent hematocompatibility, and anticoagulation properties. It is shown that magnetic properties can be tuned up in the whole superparamagnetic range. Moreover, the system has shown excellent performance in magnetic resonance imaging and liyperthermia.

By combining optical spin injection techniques with transport spectroscopy tools, we demonstrate a spin-photodetector allowing for the electrical measurement and active filtering of conduction band electron spin at room temperature in a non-magnetic GaAsN semiconductor structure. By switching the polarization of the incident light from linear to circular, we observe a Giant Spin-dependent Photoconductivity (GSP) reaching up to 40 % without the need of an external magnetic field. We show that the GSP is due to a very efficient spin filtering effect of conduction band electrons on Nitrogen-induced Ga self-interstitial deep paramagnetic centers., Comment: 4 pages, 3 figures

Flash memories based on nanoparticles (NPs) offer an attractive alternative for performance enhancement and size downscaling of non-volatile memory cells. In these devices, Coulomb blockade and quantized charging effects can be exploited at room temperature for a limited number of addressed NPs [1]. A successful exploitation of these nanoscale effects requires not only knowledge of the NPs properties (size, nature, structure and location) but also a sound understanding of the charge trapping phenomena that govern the memory behaviour of the devices. In this study, fabrication of 2D arrays pockets of Si nanocrystals (NCs) is demonstrated by implanting 1keV Si ions into thin SiO2 layer (7nm) through a stencil mask with 50nm to 2μm apertures. Upon thermal annealing, Photoluminescence spectroscopy (PL) and Energy-Filtered Transmission Electron Microscopy (EFTEM) reveal characteristics of NCs in the implanted SiO2 pockets. Then, charging dynamics examined by I(V) and I(t) measurements on nano-MOS capacitors in the 80K-300K temperature range clearly show an increasing Coulomb gap with decreasing temperature. Moreover, below a critical temperature (T=150K), N-shapes which are voltage sweep ramp dependent, appear on the I(V) curves. Comparison of the CDG capacitance extracted from QDG (charges of Dots/Gate) calculations on different I(V) ramp measurements and the CDG capacitance evaluated from structural parameters (sizes, tunnel distances…) extracted from EFTEM and PL characterizations provide relevant information regarding the kind and localization of the charge trapping centers.