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Phototherapy holds great promise in the treatment of bacterial infections, especially the multidrug resistant bacterial infections. However, most therapeutic agents are based on the integration of individual photothermal agents and photosensitizers, always in the activated state, and generally lack bacterial specificity, resulting in uncertain pharmacokinetics and serious nonspecific damage to normal tissues. Herein, we report a pH-responsive nanoplatform with synergistic chemo-phototherapy function for smart fluorescence imaging-guided precision sterilization. pH reversible activated symmetric cyanine was designed and prepared as a bacterial-specific imaging unit and PTT/PDT-in-one agent. Meanwhile, a guanidinium-based covalent organic framework (COF) was employed as a nanocarrier and chemotherapy agent to build the intelligent nanoplatform via electrostatic self-assembly. The self-assembly of the PTT/PDT-in-one agent and the COF greatly improves the stability and blood circulation of the PTT/PDT-in-one agent and provides charge-reversed intelligent targeting ability. The developed smart nanoplatform not only enables bacterial-targeted imaging but also possesses chemo/PTT/PDT synergetic high-efficiency bactericidal effects with little side effects, showing great potential in practical applications.

Radiotherapy is the main treatment for cancer patients. A major concern in radiotherapy is the radiation resistance of some tumors, such as human nonsmall cell lung cancer. However, the radiation dose delivered to the tumors is often limited by the possibility of collateral damage to surrounding healthy tissues. A new and efficient gadolinium-based nanoparticle, AGuIX, has recently been developed for magnetic resonance imaging-guided radiotherapy and has been proven to act as an efficient radiosensitizer. The amplified radiation effects of AGuIX nanoparticles appear to be due to the emission of low-energy photoelectrons and Auger electron interactions. We demonstrated that AGuIX nanoparticles exacerbated radiation-induced DNA double-strand break damage and reduced DNA repair in the H1299 nonsmall cell lung cancer cell line. Furthermore, we observed a significant improvement in tumor cell damage and growth suppression, under radiation therapy, with the AGuIX nanoparticles in a H1299 mouse xenograft model. This study paves the way for research into the radiosensitization mechanism of AGuIX nanoparticles and provides a scientific basis for the use of AGuIX nanoparticles as radiosensitizing drugs.

In spite of the rapid emergence of numerous nanoparticles (NPs) for biomedical applications, it is often challenging to precisely control, or effectively tame, the bioactivity/toxicity of NPs, thereby exhibiting limited applications in biomedical areas. Herein, we report the construction of hyaluronic acid (HA)-laminated, otherwise toxic methylviologen (MV), NPs via ternary host-guest complexation among cucurbit[8]uril, trans -azobenzene-conjugated HA, and MV-functionalized polylactic acid NPs (MV-NPs). The high, nonspecific toxicity of MV-NPs was effectively shielded (turned off) by HA lamination, as demonstrated in cells, zebrafish, and mouse models. The supramolecular host-guest interaction-mediated HA coating offered several HA-MV-NP modalities, including hyaluronidase locally and photoirradiation remotely, to precisely remove HA lamination on demand, thereby endowing materials with the capability of selective decoating-induced activation (DIA) for applications as a user-friendly herbicide, a selective antibacterial agent, or an anticancer nanomedicine. This work offers facile supramolecular coating and DIA strategies to effectively tame and precisely control the bioactivity and toxicity of functional nanomaterials for diverse applications.

As a newly emerging treatment strategy for many diseases, hydrogen therapy has attracted a lot of attention because of its excellent biosafety. However, the high diffusivity and low solubility of hydrogen make it difficult to accumulate in local lesions. Herein, we develop a H 2 self-generation nanoplatform by in situ water splitting driven by near-infrared (NIR) laser. In this work, core-shell nanoparticles (CSNPs) of NaGdF 4 :Yb,Tm/g-C 3 N 4 /Cu 3 P (UCC) nanocomposites as core encapsulated with zeolitic imidazolate framework-8 (ZIF-8) modified with folic acid as shell are designed and synthesized. Due to the acid-responsive ZIF-8 shell, enhanced permeability and retention (EPR) effect, and folate receptor-mediated endocytosis, CSNPs are selectively captured by tumor cells. Upon 980 nm laser irradiation, CSNPs exhibit a high production capacity of H 2 and active oxygen species (ROS), as well as an appropriate photothermal conversion temperature. Furthermore, rising temperature increases the Fenton reaction rate of Cu(I) with H 2 O 2 and strengthens the curative effect of chemodynamic therapy (CDT). The excess glutathione (GSH) in tumor microenvironment (TME) can deplete positive holes produced in the valence band of g-C 3 N 4 in the g-C 3 N 4 /Cu 3 P Z-scheme heterojunction. GSH also can reduce Cu(II) to Cu(I), ensuring a continuous Fenton reaction. Thus, a NIR-driven H 2 production nanoplatform is constructed for H 2 -mediated cascade-amplifying multimodal synergetic therapy.

The effect of novel silver nanowire encapsulated NaGdF 4 :Yb,Er hybrid nanocomposite on the upconversion emission and bioimaging properties has been investigated. The upconvension nanomaterials were synthesised by polyol method in the presence of ethylene glycol, PVP and ethylenediamine. The NaGdF 4 :Yb,Er-Ag hybrid was formed with upconverting NaGdF 4 :Yb,Er nanoparticles of size ~ 80 nm and silver nanowires of thickness ~ 30 nm. The surface plasmon induced by the silver ion in the NaGdF 4 :Yb,Er-Ag nanocomposite resulted an intense upconversion green emission at 520 nm and red emission at 660 nm by NIR diode laser excitation at 980 nm wavelength. The UV-Vis-NIR spectral absorption at 440 nm and 980 nm, the intense Raman vibrational modes and the strong upconversion emission results altogether confirm the localised surface plasmon resonance effect of silver ion in the hybrid nanocomposite. MRI study of both NaGdF 4 :Yb,Er nanoparticle and NaGdF 4 :Yb,Er-Ag nanocomposite revealed the T1 relaxivities of 22.13 and 10.39 mM -1  s -1 , which are larger than the commercial Gd-DOTA contrast agent of 3.08 mM -1  s -1 . CT imaging NaGdF 4 :Yb,Er-Ag and NaGdF 4 :Yb,Er respectively showed the values of 53.29 HU L/g and 39.51 HU L/g, which are higher than 25.78 HU L/g of the CT contrast agent Iobitridol. The NaGdF 4 :Yb,Er and NaGdF 4 :Yb,Er-Ag respectively demonstrated a negative zeta potential of 54 mV and 55 mV, that could be useful for biological application. The in vitro cytotoxicity of the NaGdF 4 :Yb,Er tested in HeLa and MCF-7 cancer cell line by MTT assay demonstrated a cell viability of 90 and 80 %, respectively. But, the cell viability of NaGdF 4 :Yb,Er-Ag slightly decreased to 80 and 78%. The confocal microscopy imaging showed that the UCNPs are effectively up-taken inside the nucleolus of the cancer cells, and it might be useful for NIR laser-assisted phototherapy for cancer treatment. Graphical abstract.

Photodynamic therapy (PDT) is commonly employed in clinics to treat the cancer, but because of the hypoxic tumor microenvironment prevalent inside tumors, PDT therapeutic efficiency is not adequate hence limiting the effectiveness of PDT. Therefore, we designed a nanocomposite consisting of reduced nanographene oxide (rGO) modified with polyethylene glycol (PEG), manganese dioxide (MnO 2 ), upconversion nanoparticles (UCNPs), and Chlorin e6 (Ce6) to spark oxygen production from H 2 O 2 with the aim of relieving the tumor hypoxic microenvironments. For in vivo tumor PDT and photothermal therapy (PTT), UCNPs-Ce6-labeled rGO-MnO 2 -PEG nanocomposites were used as a therapeutic agent, augmenting the therapeutic efficiency of PDT via redox progression through the catalytic H 2 O 2 decomposition pathway and further achieving excellent tumor inhibition. It is important to mention that degradation of MnO 2 in an acidic cellular microenvironment leads to the creation of a massive volume of Mn 2+ which was employed as a contrast mediator for magnetic resonance imaging (MRI). Our research postulates an approach to spark O 2 formation through an internal stimulus to augment the efficiency of MRI- and computerized tomography (CT)-imaging-guided PDT and PTT.

The use of nanoparticles (NP) as dose enhancers in radiotherapy (RT) is a growing research field. Recently, the use of NP has been extended to charged particle therapy in order to improve the performance in radioresistant tumors. However, the biological mechanisms underlying the synergistic effects involved in NP-RT approaches are not clearly understood. Here, we used the capabilities of synchrotron-based Fourier Transform Infrared Microspectroscopy (SR-FTIRM) as a bio-analytical tool to elucidate the NP-induced cellular damage at the molecular level and at a single-cell scale. F98 glioma cells doped with AuNP and GdNP were irradiated using several types of medical ion beams (proton, helium, carbon and oxygen). Differences in cell composition were analyzed in the nucleic acids, protein and lipid spectral regions using multivariate methods (Principal Component Analysis, PCA). Several NP-induced cellular modifications were detected, such as conformational changes in secondary protein structures, intensity variations in the lipid CHx stretching bands, as well as complex DNA rearrangements following charged particle therapy irradiations. These spectral features seem to be correlated with the already shown enhancement both in the DNA damage response and in the reactive oxygen species (ROS) production by the NP, which causes cell damage in the form of protein, lipid, and/or DNA oxidations. Vibrational features were NP-dependent due to the NP heterogeneous radiosensitization capability. Our results provided new insights into the molecular changes in response to NP-based RT treatments using ion beams, and highlighted the relevance of SR-FTIRM as a useful and precise technique for assessing cell response to innovative radiotherapy approaches.

Ferrous ion (Fe 2+ ) is an important component of hemoglobin and plays a role in transporting O 2 to human tissues. If iron deficiency is present, iron deficiency anemia may occur, so it is critical to develop sensitive and accurate methods to detect Fe 2+ . Herein, a novel luminescence energy transfer (ET) system has been designed for the sensitive detection of Fe 2+ by a single-particle enumeration (SPE) method in the near-infrared (NIR) region through combining NIR-to-NIR β-NaGdF 4 :Yb,Tm@NaYF 4 upconversion nanoparticles (UCNPs) and IR-808 dye. IR-808 dye can quench the luminescence of the UCNPs because of the efficient overlap between the absorption spectrum of IR-808 and the emission spectrum of the UCNPs. When Fe 2+ and H 2 O 2 are added to the system, the Fenton reaction produces hydroxyl radicals (˙OH). The generated ˙OH reacts with IR-808 and the structure of IR-808 is destroyed. As a result, the ET process is suppressed, causing recovery of the luminescence of the UCNPs, which is reflected as an increase in the number of luminescent particles. Accurate quantification of Fe 2+ is achieved by statistically counting the target concentration-dependent luminescent particles. Under the optimal conditions, the linear detection range of Fe 2+ is 5-10 000 nM, which is much wider than the ensemble luminescence spectra measurements in bulk solution. Moreover, this strategy can be applied to detection in serum samples with satisfactory results.

Detection of dopamine, an important neurotransmitter, is vital for understanding its roles in mammals and disease diagnosis. However, commonly available methods for dopamine detection typically rely on a single signal readout, which can be susceptible to interference by internal or external factors. Here, we report a dual-signal detection of dopamine based on label-free luminescent NaGdF 4 :Tb nanoparticles. In the presence of dopamine, the NaGdF 4 :Tb nanoparticles exhibit luminescence quenching under the excitation of 272 nm, while they give enhanced luminescence under 297 nm excitation, realizing both turn off and turn on detection of dopamine. The nanoparticle-based dual-signal sensors exhibit high sensitivity, with a detection limit of ∼30 nM, and good selectivity, which offers the possibility to identify potential interferents in the samples. We further demonstrate that the dual-signal response results from different energy-transfer processes within the nanoparticles under the excitation of different light. The new strategy demonstrated here should pave the way for the development of multiresponse nanosensors based on lanthanide-doped luminescent nanomaterials.

Cerium (IV) oxide (CeO 2 ), samarium (Sm) and gadolinium (Gd) doped CeO 2 nanoparticles were prepared using microwave technique. The effect of microwave irradiation time, microwave power and pH of the starting solution on the structure and crystallite size were investigated. The prepared nanoparticles were characterized using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscope. The photocatalytic activity of the as-prepared CeO 2 , Sm and Gd doped CeO 2 toward degradation of methylene blue (MB) dye was investigated under UV light irradiation. The effect of pH, the amount of catalyst and the dye concentration on the degradation extent were studied. The photocatalytic activity of CeO 2 was kinetically enhanced by trivalent cation (Gd and Sm) doping. The results revealed that Gd doped CeO 2 nanoparticles exhibit the best catalytic degradation activity on MB under UV irradiation. For clarifying the environmental safety of the by products produced from the degradation process, the pathways of MB degradation were followed using liquid chromatography/mass spectroscopy (LC/MS). The total organic carbon content measurements confirmed the results obtained by LC/MS. Compared to the same nanoparticles prepared by another method, it was found that Gd doped CeO 2 prepared by hydrothermal process was able to mineralize MB dye completely under UV light irradiation.

Since the 1980s, the broad application of gadolinium(Gd)-based contrast agents for magnetic resonance imaging (MRI) has led to significantly increased concentrations of Gd in the aqueous environment. Little is known about the stability of these highly polar xenobiotics under environmental conditions, in wastewater and in drinking water treatment. Therefore, the stability of frequently applied Gd-based MRI contrast agents towards UV radiation was investigated. The hyphenation of hydrophilic interaction liquid chromatography (HILIC) with inductively coupled plasma mass spectrometry (ICP-MS) and of HILIC with electrospray ionization mass spectrometry (ESI-MS) provided quantitative elemental information as well as structural information. The contrast agents Gd-DTPA, Gd-DOTA and Gd-BT-DO3A showed a high stability in irradiation experiments applying a wavelength range from 220 nm to 500 nm. Nevertheless, the degradation of Gd-BOPTA as well as the formation of Gd-containing transformation products was observed by means of HILIC-ICP-MS. Matrix-dependent irradiation experiments showed a degradation of Gd-BOPTA down to 3% of the initial amount in purified water after 300 min, whereas the degradation was slowed down in drinking water and surface water. Furthermore, it was observed that the sum of species continuously decreased with proceeding irradiation in all matrices. After irradiation in purified water for 300 min only 16% of the sum of species was left. This indicates a release of Gd(III) ions from the complex in course of irradiation. HILIC-ESI-MS measurements revealed that the transformation products mostly resulted from O-dealkylation and N-dealkylation reactions. In good correlation with retention times, the majority of transformation products were found to be more polar than Gd-BOPTA itself. Based on accurate masses, sum formulas were obtained and structures could be proposed., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Core-inner-valence ionization of high-Z nanoparticle atomic clusters can de-excite electrons through various interatomic de-excitation processes, thereby leading to the ionization of both directly exposed atoms and adjacent neutral atoms within the nanoparticles, and to an enhancement in photon-electron emission, which is termed the nanoradiator effect. To investigate the nanoradiator-mediated dose enhancement in the radio-sensitizing of high-Z nanoparticles, the production of reactive oxygen species (ROS) was measured in a gadolinium oxide nanoparticle (Gd-oxide NP) solution under core-inner-valence excitation of Gd with either 50 keV monochromatic synchrotron X-rays or 45 MeV protons. This measurement was compared with either a radiation-only control or a gadolinium-chelate magnetic resonance imaging contrast agent solution containing equal amounts of gadolinium as the separate atomic species in which Gd-Gd interatomic de-excitations are absent. Ionization excitations followed by ROS measurements were performed on nanoparticle-loaded cells or aqueous solutions. Both photoexcitation and proton impact produced a dose-dependent enhancement in the production of ROS by a range of factors from 1.6 to 1.94 compared with the radiation-only control. Enhanced production of ROS, by a factor of 1.83, was observed from Gd-oxide NP atomic clusters compared with the Gd-chelate molecule, with a Gd concentration of 48 μg/mL in the core-level photon excitation, or by a factor of 1.82 under a Gd concentration of 12 μg/mL for the proton impact at 10 Gy (p < 0.02). The enhanced production of ROS in the irradiated nanoparticles suggests the potential for additional therapeutic dose enhancements in radiation treatment via the potent Gd-Gd interatomic de-excitation-driven nanoradiator effect.

Purpose: To describe and quantify the different relaxation mechanisms operating in suspensions of liposomes that encapsulate paramagnetic lanthanide(III) complexes., Theory and Methods: The transverse relaxation rate of lanthanide-loaded liposomes receives contribution from the exchange between intraliposomal and bulk water protons, and from magnetic susceptibility effects. Phospholipids vesicles encapsulating different Ln(III)-HPDO3A complexes (Ln = Eu, Gd, or Dy) were prepared using the conventional thin film rehydration method. Relaxation times (T1 , T2 , and T2*) were measured at 14 Tesla (T) and 25 °C. The effect of compartmentalization of the paramagnetic agent inside the liposomal cavity was evaluated by means of an IRON-modified MRI sequence., Results: NMR measurements demonstrated that Curie spin relaxation is the dominant contribution (> 90%) to the observed transverse relaxation rate of paramagnetic liposomes. This was further confirmed by MRI that showed the ability of the liposome entrapped lanthanide complexes to generate IRON-MRI positive contrast in a size dependent manner., Conclusion: The Curie spin relaxation mechanism is by far the principal mechanism involved in the T2 shortening of the water protons in suspension of paramagnetic liposomes at 14T. The access to IRON contrast extends the potential of such nanosystems as MRI contrast agents., (© 2014 Wiley Periodicals, Inc.)

The goal of the present study was to evaluate and compare the radiosensitizing properties of gadolinium nanoparticles (NPs) with the gadolinium contrast agent (GdCA) Magnevist(®) in order to better understand the mechanisms by which they act as radiation sensitizers. This was determined following either low energy synchrotron irradiation or high energy gamma irradiation of F98 rat glioma cells exposed to ultrasmall gadolinium NPs (GdNPs, hydrodynamic diameter of 3 nm) or GdCA. Clonogenic assays were used to quantify cell survival after irradiation in the presence of Gd using monochromatic x-rays with energies in the 25 keV-80 keV range from a synchrotron and 1.25 MeV gamma photons from a cobalt-60 source. Radiosensitization was demonstrated with both agents in combination with X-irradiation. At the same concentration (2.1 mg mL(-1)), GdNPS had a greater effect than GdCA. The maximum sensitization-enhancement ratio at 4 Gy (SER4Gy) was observed at an energy of 65 keV for both the nanoparticles and the contrast agent (2.44   ±   0.33 and 1.50   ±   0.20, for GdNPs and GdCA, respectively). At a higher energy (1.25 MeV), radiosensitization only was observed with GdNPs (1.66   ±   0.17 and 1.01   ±   0.11, for GdNPs and GdCA, respectively). The radiation dose enhancements were highly 'energy dependent' for both agents. Secondary-electron-emission generated after photoelectric events appeared to be the primary mechanism by which Gd contrast agents functioned as radiosensitizers. On the other hand, other biological mechanisms, such as alterations in the cell cycle may explain the enhanced radiosensitizing properties of GdNPs.

Purpose: Accurate characterization of contrast reagent (CR) longitudinal relaxivity in whole blood is required to predict arterial signal intensity in contrast-enhanced MR angiography (CE-MRA). This study measured the longitudinal relaxation rate constants (R1 ) over a concentration range for non-protein-binding and protein-binding CRs in ex vivo whole blood and plasma at 1.5 and 3.0 Tesla (T) under physiologic arterial conditions., Methods: Relaxivities of gadoteridol, gadobutrol, gadobenate, and gadofosveset were measured for [CR] from 0 to 18 mM [mmol(CR)/L(blood)]: the latter being the upper limit of what may be expected in CE-MRA., Results: In plasma, the (1) H2 O R1 [CR]-dependence was nonlinear for gadobenate and gadofosveset secondary to CR interactions with the serum macromolecule albumin, and was well described by an analytical expression for effective 1:1 binding stoichiometry. In whole blood, the (1) H2 O R1 [CR]-dependence was markedly non-linear for all CRs, and was well-predicted by an expression for equilibrium exchange of water molecules between plasma and intracellular spaces using a priori parameter values only., Conclusion: In whole blood, (1) H2 O R1 exhibits a nonlinear relationship with [CR] over 0 to 18 mM CR. The nonlinearity is well described by exchange of water between erythrocyte and plasma compartments, and is particularly evident for high relaxivity CRs., (© 2013 Wiley Periodicals, Inc.)

This paper continues analyses on organic compounds for application in neutron dosimetry performed through electron spin resonance (ESR). Here, the authors present the results obtained by ESR measurements of a blend of ammonium tartrate dosemeters and gadolinium oxide (5 % by weight). The choice of low amount of Gd is due to the need of improving neutron sensitivity while not significantly influencing tissue equivalence. A study of the effect of gadolinium presence on tissue equivalence was carried out. The experiments show that the neutron sensitivity is enhanced by more than an order of magnitude even with this small additive content. Monte Carlo simulations on the increment of energy release due to gadolinium presence were carried, and the results were in good agreement with the experimental data., (© The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Photodynamic therapy for deep-lying lesions needs an appropriate imaging modality, precise evaluation of tissue oxygen and an effective photosensitizer. Gadolinium based metalloporphyrins Gd(III)-HMME is proposed in this study as a potential multifunctional theranostic agent, as photosensitizer, ratiometric oxygen sensor and MRI contrast agent. The time resolved spectroscopy revealed the luminescence peak of Gd(III)-HMME at 710 and 779 nm with a lifetime of 64 μs in oxygen-free methanol to be phosphorescent. This phosphorescence is strongly dependent on dissolved oxygen concentration. Its intensity in oxygen saturated methanol solution is 21% of that in deoxygenated solution. The singlet oxygen quantum yields ΦΔ of HMME and Gd(III)-HMME in air saturated methanol solution were determined to be 0.79 and 0.40 respectively using comparative spectra method. These phenomena indicate that the oxygen sensibility and production of singlet oxygen of Gd(III)-HMME can fulfill the requirement of PDT treatment.

Medical radiation imaging systems employ phosphors such as CaWO4 as X-ray receptor materials. Unfortunately, the conversion efficiencies of these materials are rather low (approx. 5%). Alternatives that comprise a bulk structure have been fabricated from rare earth metals, but they are not efficient enough to produce high quality images. Nano-phosphors do not suffer from the limitations inherent to the bulk structures of conventional phosphors. We examined the effects of sensitizer doping conditions on the optical characteristics and morphology of the rare earth phosphor Gd2O3:Eu to fabricate a novel type of nano-phosphor. We optimized a temperature solution-combustion procedure for producing phosphors doped with 5 wt% Eu. Scanning electron microscopy images showed that the phosphors were 20-30 nm in diameter and X-ray diffraction analysis revealed that they underwent polycrystalline growth upon the addition of a sensitizer, similar to the polycrystalline growth of bulk phosphors. In addition, the phosphors exhibited a strong peak at 613 nm and luminescence similar to conventional phosphors. Phosphors that were produced using citric acid as a sensitizer showed more than double the level of luminescence and could be used to produce higher quality images compared to non-sensitized phosphors. The phosphors also exhibited a high degree of luminescence stability.

The aim of this study was to quantify the dose enhancement by gadolinium and gold nanoparticles in brachytherapy. MCNPX Monte Carlo code was used to simulate four brachytherapy sources: (60)Co, (198)Au, (192)Ir, (169)Yb. To verify the accuracy of our simulations, the obtained values of dose rate constants and radial dose functions were compared with corresponding published values for these sources. To study dose enhancements, a spherical soft tissue phantom with 15 cm in radius was simulated. Gadolinium and gold nanoparticles at 10, 20 and 30 mg/ml concentrations were separately assumed in a 1 × 1 × 1 cm(3) volume simulating tumour. The simulated dose to the tumour with the impurity was compared to the dose without impurity, as a function of radial distance and concentration of the impurity, to determine the enhancement of dose due to the presence of the impurity. Dose enhancements in the tumour obtained in the presence of gadolinium and gold nanoparticles with concentration of 30 mg/ml, were found to be in the range of -0.5-106.1 and 0.4-153.1 % respectively. In addition, at higher radial distances from the source center, higher dose enhancements were observed. GdNPs can be used as a high atomic number material to enhance dose in tumour volume with dose enhancements up to 106.1 % when used in brachytherapy. Regardless considering the clinical limitations of the here-in presented model, for a similar source and concentration of nanoparticles, gold nanoparticles show higher dose enhancement than gadolinium nanoparticles and can have more clinical usefulness as dose enhancer material.

We investigate the effects of radiation on aqueous solutions of two common MRI contrast agents based on paramagnetic gadolinium chelates. Aqueous solutions of Gd-DTPA (gadolinium diethylenetriaminepentaacetic acid) and Gd-HP-DO3A (gadoteridol), as well as Gd-DTPA in the presence of concentrations of several common metabolites (N-acetylaspartate, Choline, Creatine and myo-inositol) typical of conditions in vivo, were irradiated at dose levels up to 30 Gy using a 6 MV linear accelerator and imaged using a 1.5 T MRI system. In addition, the effects of radiation dose on solution relaxation rates were compared with the effects of temperature by subjecting the same samples to varying temperatures over a range of 4 K using the same experimental conditions and imaging sequences. Radiation caused small increases (1% or less at a dose of 20 Gy) in the relaxivity of solutions. The effects of radiation on relaxivities were orders of magnitude smaller than the effects of temperature over the range in this study., (Copyright 2008 John Wiley & Sons, Ltd.)

This study has measured the longitudinal and transverse (T2* relaxivity curves for ProHance (Gadoteridol), Vasovist (Gadofosveset) and deoxyhemoglobin at 1.5, 3.0, and 7.0 Tesla. The plots of R(1) versus both contrast agent and deoxyhemoglobin concentration were linear. The plots of R2* versus deoxyhemoglobin concentration showed a quadratic dependence. R2* versus contrast agent concentration showed a parabolic dependence with a minimum occurring at contrast agent concentrations of approximately 1.5 mM, corresponding to an accessible concentration in vivo. Monte Carlo simulations were performed to support the hypothesis that the minimum results from the susceptibility of the red blood cells being matched to the susceptibility of the plasma. Relaxivity values (s(-1)mM(-1)) for R2* and R1 for all agents and all three field strengths are given., ((c) 2008 Wiley-Liss, Inc.)

Many efforts have been made to develop neutron capture therapy (NCT) for cancer treatment. Among the challenges in using NCT is the characterization of the features of the mixed radiation field and of its components. In this study, we examined the enhancement of the ESR response of pellets of alanine and ammonium tartrate with gadolinium oxide exposed to a thermal neutron beam. In particular, the ESR response of these dosimeters as a function of the gadolinium content inside the dosimeter was analyzed. We found that the addition of gadolinium improves the sensitivity of both alanine and ammonium tartrate. However, the use of gadolinium reduces or abolishes tissue equivalence because of its high atomic number (Z(Gd) = 64). Therefore, it is necessary to find the optimum compromise between the sensitivity to thermal neutrons and the reduction of tissue equivalence. Our analysis showed that a low concentration of gadolinium oxide (of the order of 5% of the total mass of the dosimeter) can enhance the thermal neutron sensitivity more than 13 times with an insignificant reduction of tissue equivalence.

In this paper, the addition of gadolinium is proposed as a useful tool to enhance the electron spin resonance (ESR) sensitivity of organic compounds to thermal neutrons. The target of this work is the detection, through the ESR technique, of the thermal neutron fluence in a mixed field of photons and neutrons. Gadolinium was chosen because it has a very high capture cross section to thermal neutrons; its nuclear reaction with thermal neutrons induces complex inner shell transitions that generate, besides other particles, Auger electrons, which in turn release their energy in the neighborhood (only several nanometers) of the place of reaction. Gadolinium was added to two organic molecules: alanine and ammonium tartrate. The main result obtained was a greater neutron sensitivity for dosimeters with gadolinium than for those without gadolinium for both organic molecules used. Since a dosimeter pair is required to discriminate between the two components of a mixed field, we studied the response of each dosimeter pair irradiated in a mixed field. Through a blind test we verified the usefulness of this dosimetric system and we obtained an estimate of the fluence in the mixed field with a relative uncertainty of 3%, when the pair composed of an alanine dosimeter and a dosimeter with alanine and gadolinium is used.

ESR response to gamma-irradiation (1-50 Gy) of blends containing alanine and either B(OH)(3) or Gd(2)O(3) is reported. The sensitivity of the alanine--B(OH)(3) blend is comparable to the sensitivity of pure alanine, although its lowest detectable dose, LDD, is smaller ( approximately 1.3 Gy) than that of pure alanine ( approximately 2.9 Gy). Alanine with Gd(2)O(3) is about two times more sensitive than pure alanine, and its LDD is 0.8 Gy. The better sensitivity and LDD are probably due to the high atomic number (Z=64) of gadolinium, which enhances the interaction probability with photons and, consequently, the radical yield. This study suggests that other high-Z atoms may be useful for increasing the sensitivity of the response of alanine to gamma-radiation.

Uniform Gd2O3 : Eu3+ nanowires were fabricated by using anodic aluminum oxide template (AAO). The spectral measurements indicate that with the increasing annealing temperature the excitation band of Eu3+ in Gd2O3 : Eu3+ nanowires/AAO shifted blue, the intensity ratio of 5D0-7F2 to 5D0-7F1, decreased, and the lifetime became longer. In the sample annealed at 1000 degrees C two spectral components, the sharper and broader lines were identified, corresponding to two different local environments, the Eu3+ ions in cubic phase and in amorphous phase, respectively. The 5D0-7F1 transitions of Eu3+ ions in cubic phase had longer lifetime than that in amorphous phase. In contrast to the lifetime of the 5D0-7F(j) transitions in the bulk, that in Gd2O3 : Eu3+/AAO composite films increased due to influence of the surrounding media (AAO).

Nanocrystalline GdPO4 : Eu3+ phosphor layers were coated on non-aggregated, monodisperse and spherical SiO2 particles by Pechini sol-gel method, resulting in the formation of core-shell structured SiO2 @ GdPO4 : Eu3+ particles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), time-resolved PL spectra and lifetimes were used to characterize the core-shell structured materials. Both XRD and FT-IR results indicate that GdPO4 layers have been successfully coated on the SiO2 particles, which can be further verified by the images of FESEM and TEM. Under UV light excitation, the SiO2 @ GdPO4 : Eu3+ phosphors show orange-red luminescence with Eu3+ 5D0-7F1 (593 nm) as the most prominent group. The PL excitation and emission spectra suggest that an energy transfer occurs from Gd3+ to Eu3+ in SiO2 @ GdPO4 : Eu3+ phosphors. The obtained core-shell phosphors have potential applications in FED and PDP devices.

Lithium-gadolinium-borate (LGB) dispersed as microcrystals within the plastic scintillator BC-490 is a promising material for accurate neutron dosimetry in mixed n/gamma fields. Spectral information > 1 MeV is obtained by capture gating proton recoil events in the plastic scintillator to subsequent capture in (6)Li. Below 1 MeV, isolated capture events in either gadolinium or (6)Li give energy information in this region. Discrimination based on capture gating is used to reject false coincidences due to gamma rays or incorrectly gated neutron events. A detailed Monte Carlo model has been created in MCNPX that predicts the energy response of the LGB spectrometer in the capture-gated mode of operation. X-ray microtomography has been performed on the detector in order to obtain the LGB microcrystal distribution within the plastic scintillator, and this is incorporated into the model. The way in which the calculated response functions can be included in an unfolding procedure is outlined.

A uniform nanolayer of europium-doped Gd2O3 was coated on the surface of preformed submicron silica spheres by a Pechini sol-gel process. The resulted SiO2 @ Gd2O3:Eu3+ core-shell structured phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays. The XRD results show that the Gd2O3:Eu3+ layers start to crystallize on the SiO2 spheres after annealing at 400 degrees C and the crystallinity increases with raising the annealing temperature. The core-shell phosphors possess perfect spherical shape with narrow size distribution (average size: 640 nm) and non-agglomeration. The thickness of the Gd2O3:Eu3+ shells on the SiO2 cores can be adjusted by changing the deposition cycles (70 nm for three deposition cycles). Under short UV excitation, the obtained SiO2@Gd2O3:Eu3+ particles show a strong red emission with 5D0-7F2 (610 nm) of Eu3+ as the most prominent group. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

Some selected materials with small sizes in the nanometer region are reviewed. Different methods for synthesis of nanoscale materials are classified and discussed. Basic prerequisites for successful use of the materials for nanotechnology application are their synthesis with specific and homogeneous composition and geometry. This review summarizes recent results on nanoscale materials containing optically active lanthanide ion especially focused on Y2O3 and Gd2O3 oxide.

The luminescence properties of a Pr3+-doped gadolinium gallium garnet (GGG, Gd3Ga5O12) nanocrystalline host were investigated. Dominant blue/green emission was observed emanating from the 3P0 --> 3H4 transition after excitation using a wavelength of 457.9 nm. Continuous wave excitation into the 1D2 level of the Pr3+ ion at 606.9 nm transition produced blue upconversion luminescence spectra, ascribed to emission from the 3P1 --> 3H4 and 3P0 --> 3H4 transitions. The increase in the decay times of the observed transitions following excitation with 606.9 nm is indicative of the dominance of an energy transfer upconversion (ETU) mechanism relative to excited state absorption (ESA). Furthermore, blue, green and red upconversion emission was observed from the 3P0, 3P1 and 1D2 states following excitation into the 1G4 energy level with 980 nm. No change in the decay times of the emitting states was observed following excitation with a wavelength of 980 or 457.9 nm; hence, upconversion was determined to primarily occur through ESA. The luminescence properties of the nanocrystals are compared to a single crystal of GGG:Pr3+ (bulk) with an identical Pr3+ concentration (1%).

A pMOSFET having a 10 microm thick Gadolinium (Gd) layer has been invented as a slow neutron sensor. When slow neutrons are incident to the Gd layer, conversion electrons, which generate electron-hole pairs in the SiO2 layer of the pMOSFET, are generated by a neutron capture process. The holes are easily trapped in the oxide and act as positive-charge centres in the oxide. Due to the induced charges, the threshold turn-on voltage of the pMOSFET is changed. The developed sensors were tested at a neutron beam port of the HANARO research reactor and a 60Co irradiation facility to investigate slow neutron response and gamma ray contamination, respectively. The resultant voltage change was proportional to the accumulated neutron dose and it was very sensitive to slow neutrons. Moreover, ionising radiation contamination was negligible. It can also be used in a mixed radiation field by subtracting the voltage change of a pMOSFET without Gd from that of the Gd-pMOSFET.

Accurate estimation of neutron dose requires knowledge of the neutron energy distribution in the working environment. Existing neutron spectrometry systems, Bonner spheres for example, are large and bulky, and require long data acquisition times. A portable system that could indicate the approximate neutron energy spectrum in a short time would be extremely useful in radiation protection. A composite scintillator, consisting of lithium gadolinium borate crystals in a plastic scintillator matrix, produced by Photogenics is being tested for this purpose. A prototype device based on this scintillator and digital pulse processing electronics has been calibrated using quasi-monoenergetic neutron fields at the low-scatter facility of the UK National Physical Laboratory (NPL). Energies selected were 144, 250, 565, 1400, 2500 and 5000 keV, with correction for scattered neutrons being made using the shadow cone technique. Measurements were also made in the NPL thermal neutron field. Pulse distributions collected with the digitiser in capture-gated mode are presented, and detection efficiency and energy resolution derived. For comparison, neutron spectra were also collected using the commercially available Microspec N-Probe from Bubble Technology Industries, which consists of an NE213 scintillator and a 3He proportional counter.

Optical and dosimetric properties of nominally pure CsGd2F7 crystals and of CsGd2F7 crystals doped with various concentrations of Pr3+ ions were investigated. Effects of X, beta and UV irradiation on these crystals were studied. Methods of optical absorption, X and UV excited luminescence, thermoluminescence (TL), phototransferred thermoluminescence and optically stimulated luminescence were used in these investigations. The dependence of the TL efficiency on the radiation dose was found to be linear up to 6 kGy for the 3 at.% Pr3+ doped samples. The crystals containing from 0.3 at.% to 1.0 at.% of Pr3+ ions were found to have the best TL sensitivity and the intensity of the main TL peak in these samples was more than two orders of magnitude higher than that of the pure crystals. The TL sensitivity of the CsGd,F7:Pr3+ crystals was also compared with that of other commonly used TLD materials.

The phosphor GdO2S:Tb is widely used in camera-based electronic portal imaging devices (EPIDs). There is considerable interest in the application of EPIDs to dosimetry and the verification of intensity modulated radiation therapy produced by dynamic multileaf collimation (DMLC). This paper presents direct measurement of Gd2O2S:Tb phosphor luminescence under 6 MV x-ray irradiation from a linear accelerator using a photomultiplier tube. The luminescence following each radiation pulse (3 micros duration) was observed to decay with a dominant lifetime of 558 micros. Using a specialized electrometer, the temporal variation of the optical signal has been compared with the dose rate incident on the phosphor measured using a semiconductor diode detector. Under dose rates typical of those used in the clinic (1.2 Gy min(-1) to the phosphor), measurements at beam-start confirmed that the optical signal is linear with dose per radiation pulse. Measurements at beam termination following phosphor doses up to 4.4 Gy showed no residual signal associated with long-lived luminescence (afterglow) from the phosphor above the noise level of the optical signal (0.17% standard deviation). This measurement demonstrates that afterglow from Gd2O2S:Tb is not of significance for its application to DMLC verification. Additionally, it was confirmed that the accelerator pulse repetition frequency has no effect on the optical signal from the phosphor in the range 25-400 Hz.

In gadolinium-neutron capture reactions, prompt gamma rays with an energy spectrum of up to 7 MeV, X-rays and electrons are released. We measured the effect of radiation as a result of capture reactions on cultured Chinese hamster cells. Cells in the medium containing 5000 ppm gadolinium were exposed to thermal neutrons from a nuclear reactor. The survival curve for those cells exhibited a shoulder in the low neutron fluence region. The survival curve for cells exposed to thermal neutrons in the absence of gadolinium was a simple exponential function. To obtain 10% survival levels, 5.4 x 10(12) neutrons/cm2 were required for cells irradiated in the absence of gadolinium, and 1.55 x 10(12) neutrons/cm2 for those irradiated in the presence of gadolinium. The therapeutic ratio in gadolinium-neutron capture therapy depends on the difference in 157Gd concentrations between the tumor and normal tissues. Thus, our current effort has been to develop a method of selectively delivering 157Gd to tumors.

Irradiation of plasmid DNA/Gd3+ mixtures with thermal neutrons induces DNA double-strand breaks (dsb). However, the extent of breakage is markedly reduced by sequestering the Gd3+ from DNA by addition of EDTA. Since the 157Gd neutron capture event involves some internal conversion, we suggest that the DNA dsb induction results from Auger electron emission.