In this study, we report the synthesis and characterization of nitroxide-functionalized silica nanoparticles incorporating a TEMPO-based spin label. These nanoparticles were prepared through a reverse microemulsion method, and the nitroxide moiety was introduced via a TEMPO-modified silane, synthesized by coupling 4-amino-TEMPO with 3-(triethoxysilyl)propylsuccinic anhydride. By adjusting experimental parameters, we successfully modulated the radical surface density, obtaining values ranging from 0.36 to 2.83 radicals/nm2, as determined by UV spectroscopy. Relaxometric measurements showed that both longitudinal (r1) and transverse (r2) relaxivities were strongly influenced by radical density, reaching maximum values of 5.42 and 11.94 s-1·mM-1, respectively, corresponding to enhancements of up to 489% (r1) and 712% (r2) compared to free 4-amino-TEMPO (at 20 MHz). Interestingly, high surface loading led to a decrease in relaxivity, highlighting the role of spin-spin interactions in modulating the relaxation process. Phantom electron paramagnetic resonance imaging (EPRI) demonstrated improved contrast and resolution for formulations with low radical densities, highlighting the importance of surface engineering to optimize the nanoparticle performance for EPRI applications.

Visible fiber laser have attained significant attention initially employing fluoride glass (ZBLAN) fibers, and lately achieving 5W output power at 635 nm from a praseodymium (Pr)-doped fiber lasers [1]. Recently, also dysprosium (Dy)-doped silica fiber lasers have been first demonstrated [2]. This is important because the oxide-based fibres are typically superior to ZBLAN based on their mechanical and thermal properties.

The glass-powder-nanocrystals (NCs) method was investigated as a powerful technique to develop new optical fibers in the context of fiber lasers and amplifiers applications. The advantage of this method is the independent preparation of NCs and matrix glass, which gives full control of the crystal phase and active ion concentration of the NCs as well as the refractive index of the glass, resulting in index matching. We demonstrated the survival of YPO4:Yb3+ and Al2O3:Cr3+ NCs in defect-free short optical fibers, pointing out essential key issues like optimization of the NCs content in the core and their mixing procedure as well as densification (pressing and pre-sintering) of the core material and effective route to lower scattering losses using smaller NCs size (150 nm). The importance of avoiding secondary crystallization has been discussed in the example of embedding two different NCs in the commercial Ohara glass matrix. In developed YPO4:Yb3+ doped optical fiber, we achieved a relatively large on/off gain coefficient of about 1 dB/cm. This result makes glass-powder-doped fibers interesting for fiber sensors and promising for fiber lasers and amplifier applications after further optical quality improvement.

The two sites water exchange model (2SWEM) and the three sites exchange model (3SEM) were properly used to describe proton (1H) magnetic relaxation dispersion (1HMRD) in human serum albumin (HSA) solutions at 310 K. Lyophilized HSA was obtained from Sigma-Aldrich and diluted in phosphate buffered saline (PBS, pH 7.4) to obtain 10 samples with a concentration of 50 g/l. The 1HMRD profiles (20–60 MHz) were obtained using a fast field cycling nuclear magnetic resonance relaxometry facility (Stelar FFC 2000 Spinmaster) and two Minispec (Mq20, Mq60) relaxometry facilities from Bruker. The longitudinal 1H magnetic relaxation time (T1) was measured employing the inversion recovery pulse sequence and the 1/T1 was plotted as a function of the frequency of resonance to create the 1HMRD profiles. The 2 sites water exchange model considering ellipsoidal geometry is the best option to fit the 1HMRD profiles in diluted HSA solutions, which allows to update the physical model previously presented to describe the theoretical dependence between the transverse proton magnetic relaxation rate and the protein dynamic viscosity in blood plasma and blood serum solutions. The physical parameters obtained from the fit, using this model, describe properly the diluted HSA solutions in comparison with previous experimental reports and theoretical estimations. This result can be improved taking into consideration all the proton–proton dipolar interactions of the protons belonging to the bound water molecules.

Bacterial flocculation is a process in which bacteria aggregate to form cloudy, flake-like clusters known as flocs. While this phenomenon is commonly associated with water treatment, it also has interesting industrial applications, particularly as a method for cell immobilisation. Escherichia coli, extensively employed in industrial processes, typically does not possess inherent flocculation ability. In this study, we found that certain bisbenzimidazole derivatives can rapidly induce flocculation in E. coli (K-12 MG1655) in a structure-dependent manner. Among others, high-resolution microscopy (SEM, fluid AFM) revealed a dense fibrillar network within the flocs, initially suggestive of an extracellular matrix. Mechanistic investigations demonstrated that this phenomenon cannot be linked to the secretion of extracellular polymeric substances (EPS). Our findings suggest that flocculation arises from the self-assembly of bisbenzimidazole derivatives into supramolecular fibres that anchor to bacterial membranes. These results uncover an atypical flocculation process distinct from charge neutralisation or EPS-mediated pathways, broadening the potential applications of bisbenzimidazole derivatives in bacterial immobilisation.

Electron paramagnetic resonance (EPR) spectroscopy is a tool that provides sensitive detection of uncoupled electron spins for a variety of applications. This technique enables the specific detection and quantification of radical species while also being able of generating high-contrast, background-free images. However, the EPR labeling and imaging techniques encounter limitations mainly due to the instability of organic radicals from organic probes, which can influence the reliability and scope of the experiment. In that context, the use of nanodiamonds (NDs) in EPR may be a promising route for understanding their unique properties and potential biomedical applications. The ability to perform EPR imaging in combination with the stable intrinsic properties of paramagnetic centers within these particles raises the possibility of extending nanodiamond-based imaging capabilities. Herein, we present a preliminary demonstration of a practical spectroscopy and imaging application using nanosized diamond particles (<18 nm) for electron paramagnetic resonance imaging (EPRI). The discretization of two different nanodiamond production sources among the most studied NDs (HPHT or detonation) allows further characterization of their physicochemical properties. In addition, we have investigated variations in the physicochemical properties of nanodiamonds, including size effects and surface treatments. Finally, we provide experimental evidence of the conditions required for optimal spectroscopic and imaging resolution (R < 1 mm) as well as achievable EPR sensitivity.

Experimental results on optical properties of Tm-doped oxide glass fibres based on different technologies and host materials are presented. Silica fibres and crystal-derived fibres (CDF) are compared. Crystal-derived fibres offer potentially higher doping levels than those made by Modified Chemical Vapor Deposition technology providing the ability to tune optical properties towards new applications. A detailed analysis of absorption and fluorescence properties of the 3F4 and 3H4 levels within a concentration range from 0.08 up to 1.52 mol% Tm2O3 is provided resulting in an extensive and specific energy level scheme for 789nm core-pumping.

We will report on recent advances in fabrication of large volume silica based, doped fiber preform materials synthesized via powder-based processes. Recently, there has been increased interest for power scaling in fiber based laser applications that requires large core volumes with excellent homogeneity in refractive indices, but also chemical variety (in terms of high dopant concentrations, different dopants). A structural fiber variety requires dedicated large volume core material of reproducible and tailorable chemical composition. Established technologies such as modified chemical vapor deposition (MCVD) or crucible melting rely on complex thermal processing, and are limited in accessible chemistries, dopant concentration, achievable functionalities, and in case of MCVD in achievable core sizes. The current process development thus targets to overcome such draw-backs by including novel approaches to enable extreme material combinations, enhanced reactivity, or novel functions.

Optical fiber with YPO4:Pr3+ nanocrystals (NCs) is presented for the first time using the glass powder—NCs doping method. The method’s advantage is separate preparation of NCs and glass to preserve luminescent and optical properties of NCs once they are incorporated into optical fiber. The YPO4:Pr3+ nanocrystals were synthesized by the co-precipitation and hydrothermal methods, optimized for size (< 100 nm), shape, Pr3+ ions concentration (0.2 mol%), and emission lifetime. The core glass was selected from the non-silica P2O5-containing system with refractive index (n = 1.788) close to the NCs (no = 1.657, ne = 1.838). Optical fiber was drawn by modified powder-in-tube method after pre-sintering of glass powder—YPO4:Pr3+ (wt 3%) mixture to form optical fiber preform. Luminescent properties of YPO4:Pr3+ and optical fiber showed their excellent agreement, including sharp Pr3+ emission at 600 nm (1D2–3H4) and 1D2 level lifetime (τ = 156 ± 5 µs) under 488 nm excitation. The distribution of the YPO4:Pr3+ NCs in optical fiber were analyzed by TEM-EDS in the core region (FIB-SEM-prepared). The successful usage of glass powder—NCs doping method was discussed in the aspect of promising properties of the first YPO4:Pr3+ doped optical fiber as a new way to develop active materials for lasing applications, among others.

Using well-established measurement techniques like transmission electron microscopy (TEM), dynamic light scattering (DLS), small and wide angle X-ray scattering (SAXS, WAXS), susceptometry, and magnetorelaxometry, the distribution of the physical and magnetic size (magnetic moments) and magnetic anisotropy of a variety of structurally different magnetic nanoparticle samples (MNPs) is analyzed and compared. A term which accounts for the presence of weak magnetic areas (WMAs) within the MNPs was introduced to the widespread analysis model for M(H) data, enabling a consistent interpretation of the data in most of the systems. A comparison of the size distributions as obtained for the physical and the magnetic diameter suggests a multidomain structure for three single core systems under investigation, in all probability evoked by the presence of a wustite phase, as identified by WAXS.Analyzing the relationship d < dm < dc between the average single core diameter d, the effective magnetic (domain) size dm and the cluster diameter dc quantitatively, two qualitatively different magnetic structures in multicore MNP (MCMNP) systems were identified: (i) The magnetic moments of single cores within the MCMNP of fluidMAG tend to build flux closure structures, driven by dipole-dipole interaction. (ii) The magnetic behavior of Resovist & REG; was attributed to the presence of domain sizes of about 12 nm within MCMNP, exceeding the single core diameters of 5 nm. Thereby, WAXS revealed a bimodal crystallite size distribution suggesting a crystallite merging process within the MCMNP. The value of the effective magnetic moment of these MCMNP could be explained within the presented "random moment cluster model" (RMCM).We conclude that the combination of physical and magnetic structure parameters obtained from complementary measurement methods allows a reliable assessment of the magnetic structure of single and multicore MNPs.

Rare-earth-doped optical fibres had a tremendous impact on the telecom as well as the laser market.

Among the plethora of nanosystems used in the field of theranostics, iron oxide nanoparticles (IONPs) occupy a central place because of their biocompatibility and magnetic properties. In this study, we highlight the radiosensitizing effect of two IONPs formulations (namely 7 nm carboxylated IONPs and PEG5000-IONPs) on A549 lung carcinoma cells when exposed to 225 kV X-rays after 6 h, 24 h and 48 h incubation. The hypothesis that nanoparticles exhibit their radiosensitizing effect by weakening cells through the inhibition of detoxification enzymes was evidenced by thioredoxin reductase activity monitoring. In particular, a good correlation between the amplification effect at 2 Gy and the residual activity of thioredoxin reductase was observed, which is consistent with previous observations made for gold nanoparticles (NPs). This emphasizes that NP-induced radiosensitization does not result solely from physical phenomena but also results from biological events.

As an emerging technology, molecular imaging combines advanced imaging technology with cellular and molecular biology to highlight physiological or pathological processes in living organisms at the cellular level. The main advantage of in vivo molecular imaging is its ability to characterize pathologies of diseased tissues without invasive biopsies or surgical procedures. Such technology provides great hope for personalized medicine and drug development, as it can potentially detect diseases in early stages (screening), identify the extent of a disease/anomaly, help to apply directed therapy, or measure the molecular-specific effects of a given treatment. Molecular imaging requires the combination of high-resolution/sensitive instruments with targeted imaging agents that correlate the signal with a given molecular event. In ongoing preclinical studies, new molecular targets, which are characteristic of given diseases, have been identified, and as a consequence, sophisticated multifunctional probes are in perpetual development. In this context, the discovery of new emerging chemical technologies and nanotechnology has stimulated the discovery of innovative compounds, such as multimodal molecular imaging probes, which are multiplex systems that combine targeting moieties with molecules detectable by different imaging modalities.

Despite significant advances in cancer therapy over the years, its complex pathological process still represents a major health challenge when seeking effective treatment and improved healthcare. With the advent of nanotechnologies, nanomedicine-based cancer therapy has been widely explored as a promising technology able to handle the requirements of the clinical sector. Superparamagnetic iron oxide nanoparticles (SPION) have been at the forefront of nanotechnology development since the mid-1990s, thanks to their former role as contrast agents for magnetic resonance imaging. Though their use as MRI probes has been discontinued due to an unfavorable cost/benefit ratio, several innovative applications as therapeutic tools have prompted a renewal of interest. The unique characteristics of SPION, i.e., their magnetic properties enabling specific response when submitted to high frequency (magnetic hyperthermia) or low frequency (magneto-mechanical therapy) alternating magnetic field, and their ability to generate reactive oxygen species (either intrinsically or when activated using various stimuli), make them particularly adapted for cancer therapy. This review provides a comprehensive description of the fundamental aspects of SPION formulation and highlights various recent approaches regarding in vivo applications in the field of cancer therapy.

We investigate Tm-doped double-clad fibers drawn from fused silica preforms with inserted Tm:YAG laser crystal rods. Based on the Molten-Core-Method the drawn crystal-derived fibers show typical amorphous properties covering a Tm concentration range from 0.2 to 0.84 mol% Tm2O3. They are studied in terms of their suitability of for multi-Watt level fiber lasers and compared to a Tm-laser fiber conventionally fabricated by Modified Chemical Vapor Deposition and solution doping. For the crystal-derived fibers, we demonstrate up to 4 W output power around 2 μm emission wavelength and a slope efficiency of 47 %, which are to date the highest achieved values for 790 nm pumping.

Optical properties of Tm-doped fibres based on two different host glasses, silica-based and Yttrium-Aluminium-Garnet (YAG) derived, are compared. Crystal-derived fibres (CDF) offer a wider range of core compositions than those made by Modified Chemical Vapor Deposition (MCVD) and offer the ability to tune optical properties towards new applications. Absorption and emission behaviour, including absorption cross-sections, fluorescence intensities and lifetimes of the ${{}^{3}\mathrm{F}}_{4}$ and ${{}^{3}\mathrm{H}}_{4}$ level, are investigated in the wavelength range from 200 to 2100 nm and in a concentration range from 0.08 up to 1.52 mol% $\text{Tm}_{2}\mathrm{O}_{3}$ .

Background:Alzheimer's disease (AD) is a neurodegenerative disorder lacking any curative treatment up to now. Indeed, actual medication given to the patients alleviates only symptoms. The cytosolic phospholipase A2 (cPLA2-IVA) appears as a pivotal player situated at the center of pathological pathways leading to AD and its inhibition could be a promising therapeutic approach. Objective:A cPLA2-IVA inhibiting peptide was identified in the present work, aiming to develop an original therapeutic strategy. Methods:We targeted the cPLA2-IVA using the phage display technology. The hit peptide PLP25 was first validated in vitro (arachidonic acid dosage [AA], cPLA2-IVA cellular translocation) before being tested in vivo. We evaluated spatial memory using the Barnes maze, amyloid deposits by MRI and immunohistochemistry (IHC), and other important biomarkers such as the cPLA2-IVA itself, the NMDA receptor, AβPP and tau by IHC after i.v. injection in APP/PS1 mice. Results:Showing a high affinity for the C2 domain of this enzyme, the peptide PLP25 exhibited an inhibitory effect on cPLA2-IVA activity by blocking its binding to its substrate, resulting in a decreased release of AA. Coupled to a vector peptide (LRPep2) in order to optimize brain access, we showed an improvement of cognitive abilities of APP/PS1 mice, which also exhibited a decreased number of amyloid plaques, a restored expression of cPLA2-IVA, and a favorable effect on NMDA receptor expression and tau protein phosphorylation. Conclusions:cPLA2-IVA inhibition through PLP25 peptide could be a promising therapeutic strategy for AD.

In the present work, we report on the preparation of silicate glass containing crystals by means of melting a mixture of YbPO4 xenotime structured crystals and SiO2 nanoparticles. This nanoparticle mixture is used for preparation of large volume core preforms for laser active optical fiber. Temperature dependent sintering and fiber drawing experiments at temperatures up to about 2000 °C were conducted in order to assess the integrity of the crystals in the preform and fiber, respectively. The survival of YbPO4 crystalline particles in silica was investigated by X-ray diffraction (XRD), electron probe microanalysis (EPMA), Raman spectroscopy as well as static and time resolved fluorescence measurements. It was found that the particles withstand the high-temperature steps during the fiber fabrication process. XRD and spectroscopic measurements suggest that the Yb ions are located in a crystalline but also in an amorphous silica-dominated surrounding in the fiber, suggesting the partial decomposition of the crystals during the fiber fabrication.

Magnetic nanocomposites are a class of smart materials that have attracted recent interest as drug delivery systems or as medical implants. A new approach toward the biocompatible nanocomposites suitable for remote melting is presented. It is shown that magnetite nanoparticles (MNPs) can be embedded into a matrix of biocompatible thermoplastic dextran esters. For that purpose, fatty acid esters of dextran with adjustable melting points in the range of 30-140 & DEG;C were synthesized. Esterification of the polysaccharide by activation of the acid as iminium chlorides guaranteed mild reaction conditions leading to high-quality products as confirmed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy as well as by gel permeation chromatography (GPC). A method for the preparation of magnetically responsive bionanocomposites (BNCs) was developed consisting of combined dissolution/suspension of the dextran ester and hydrophobized MNPs in an organic solvent followed by homogenization with ultrasonication, casting of the solution, drying and melting of the composite for a defined shaping. This process leads to a uniform distribution of MNPs in BNC as revealed by scanning electron microscope (SEM). Samples of different geometries were exposed to high-frequency alternating magnetic field (AMF). It could be shown that defined remote melting of such biocompatible nanocomposites is possible for the first time. This may lead to a new class of magnetic remote-control systems, which are suitable for controlled release applications or self-healing materials. BNCs containing biocompatible dextran fatty acid ester melting close to human body temperature were prepared and loaded with Rhodamine B (RhB) or green fluorescent protein (GFP) as model drugs to evaluate their potential use as drug delivery system. The release of the model drugs from the magnetic BNC investigated under the influence of a high-frequency AMF (20 kA/m at 400 kHz) showed that on-demand release is realized by applying the external AMF. The BNC possessed a long-term stability (28 d) of the incorporated iron oxide particles after incubation in artificial body fluids. Temperature-dependent mobility investigations of MNP in the molten BNC were carried out by optical microscopy, magnetometry, alternating current (AC) susceptibility, and Mossbauer spectroscopy measurements. Optical microscopy shows a movement of agglomerates and texturing in the micrometer scale, whereas AC susceptometry and Mossbauer spectroscopy investigations reveal that the particles perform diffusive Brownian motion in the liquid polymer melt as separated particles rather than as large agglomerates. Furthermore, a texturing of MNP in the polymer matrix by a static magnetic field gradient was investigated. First results on the preparation of cross-linkable dextran esters are shown. Cross-linking after irradiation of the BNC prevents melting that can be used to influence texturing procedures.

Incorporating new optical materials as nanocrystals into glass fibres for new functionalities has recently become a hot research topic. Our team (funded by the European FET Open project NCLAS) investigates the introduction of nanoscale laser crystallites into the core of optical fibres using the glass powder doping method. Active Y2O3:Pr3+ nanocrystals (NCs) were prepared via different synthesis methods, and structurally and spectroscopically characterized. After modification of technological parameters, the optimised NCs have been proposed as a luminescence centres to embed into germanate and silicate glass hosts. Glasses were analysed in terms of optical (transmission, refractive index matching to NCs) and thermal (thermal stability, viscosity, thermal expansion coefficient) parameters. Crystallisation issues during fibre drawing were particularly investigated. In a first step, glass powder-NCs mixing techniques and fibre preform preparation were developed. It was shown that temperature cycle profiles including dwell time and heating/cooling ramp rates influenced the glass-NCs properties and can lead to glass crystallisation or NCs dissolution. The sintering investigations pointed out the melting temperature limits to preserve active NCs in the glasses. In germanate glasses, Y2O3:Pr3+ dissolution was noticed at 800°C. In the case of the silicate glass compositions these regions vary from 700°C to 1050°C. The results allowed to select optical fibre drawing conditions performed by the powder-in-tube method. Their distribution uniformity is not yet sufficient, requiring further optimisation of the drawing kinetics.