R1 Values Research Articles

Evaluating size‐dependent relaxivity of PEGylated‐USPIOs to develop gadolinium‐free T1 contrast agents for vascular imaging

Ultra-small superparamagnetic iron oxide (USPIO) nanoparticles provide a safer alternative to gadolinium-based contrast agents (GBCAs) in T1-weighted MR imaging. MRI contrast behavior of USPIOs depends on their magnetic properties, which in turn depend on their physicochemical composition. Identifying and tailoring USPIO structural characteristics that influence proton relaxation in MRI is crucial to developing effective gadolinium-free T1 contrast agents. Here, we present a systematic empirical evaluation of the relationship between USPIO size and MRI relaxivity (r1 and r2 values). Monodisperse USPIO cores, with precisely controlled core diameter (dC ) were synthesized via the thermal decomposition of iron(III)-oleate precursor. USPIOs with dC = 6.34, 7.58, 8.58, and 9.50nm, were dispersed in aqueous phase via ligand exchange with silane or dopamine-modified polyethylene glycol (PEG) polymers. Relaxivity characterization in a 1.5 T clinical MRI scanner showed the r2 /r1 ratio increased linearly with USPIO core diameter (R2 = 0.95), but varied little with both hydrodynamic diameter (dH ) and PEG molecular weight. One sample, DOPA-6-20 (6.34nm USPIO cores coated with 20 kDa dopamine-modified PEG), provided the lowest r2 /r1 value (3.44) and thus promise as a potential T1 contrast agent. In a preliminary study, we evaluated DOPA-6-20 for in vivo angiography imaging in a mouse with a 7 T scanner and observed strong T1-weighted enhancement of the mouse blood pool. Key anatomical features in the vascular network were visible even 5 min after intravenous administration. Using empirical data, we have presented the basis of a structure-property relationship that can help develop optimized USPIO-based T1 contrast agents. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2440-2447, 2018.

Impact of ligands structure on formation of hydrophilic colloids from their Gd(III) complexes with high magnetic relaxivity

The present paper introduces specific structure of thiacalix[4]arenes derivatives adopting 1,3-alternate conformation with alkyl-carboxyl substituents as ligands for conversion of their complexes with Gd(III) ions into hydrophilic colloids with longitudinal (r1) and transverse relaxivities (r2) higher than that of Gd(III)-based commercial contrast agents (r1 = 20.53 and r2 = 23.46 mM−1 s−1 at 0.47 T). pH-dependent coordination of Gd(III) ions via carboxyl substituents of the thiacalix[4]arenes is the driving force for the complex formation, while the precipitation of the complexes is the basis for the colloids formation. Tert-butyl and butyl substituents of thiacalix[4]arenes were found to be of crucial impact on the complex precipitation. The specific inner- and outer-sphere ligand environment provided by the thiacalix[4]arene ligands was revealed as the optimal for high r1 and r2 values of the colloids. High relaxivities along with negligible cytotoxicity open up the possibility of their further use as positive contrast agents in magnetic resonance imaging (MRI).

Ultra-small Albumin Templated Gd/Ru Composite Nanodots for In Vivo Dual modal MR/Thermal Imaging Guided Photothermal Therapy.

Multifunctional theranostic nanoagents which realize precise diagnosis and treatment of tumors are attracting increasing interests in recent years. However, efficient and controlled synthesis of ultra-small noble metal nanoagents remains a challenge. Here, monodisperse Gd/Ru@BSA nanodots (GRBNDs) are successfully fabricated via a totally "green", "one-pot" protocol for in situ reduction of Ru(III) and biomineralization of Gd(III) in the presence of albumin. The as-prepared nanoagent possesses the features of being ultra small in size (≈6.7 nm), having strong colloidal stability, and thermal stability as well as high photothermal conversion efficiency (η = 50.7%). As expected, the GRBNDs achieve a significant efficacy of anticancer therapy under LASER activation both in vitro and in vivo. It also exhibits superior T1 -weighted magnetic resonance (MR) imaging ability due to its high longitudinal relaxivity value (r1 = 10.98 × 10-3 m-1 s-1 ). Moreover, it is demonstrated to be renal clearable with negligible systemic toxicity. This work highlights a straightforward and repeatable approach for synthesizing highly effective and multifunctional noble metal nanoagent of great clinical promising for cancer theranostics.

Tumor-triggered transformation of chimeric peptide for dual-stage-amplified magnetic resonance imaging and precise photodynamic therapy

Despite the great success in clinical magnetic resonance imaging (MRI), Gd3+-based contrast agents still suffer from low proton relaxation efficiency, rapid metabolic clearance as well as poor sensitivity. In this work, we designed a matrix metalloproteinase-2 (MMP-2) responsive chimeric peptide for dual-stage-amplified MRI and precise photodynamic therapy. Both in vitro and in vivo studies indicated that this chimeric peptide could self-assembly into spherical nanoparticles at physiological condition with r1 value of 28.17 mM−1s−1. Meanwhile, the spherical shape endowed chimeric peptide with efficient tumor accumulation via enhanced penetration and retention (EPR) effect. Importantly, the overexpressed MMP-2 in tumor region could specifically hydrolyze chimeric peptide, leading to sphere-to-fiber transformation. This transformation enhanced both the tumor accumulation and the relaxivity of contrast agent. Consequently, the r1 value was remarkably elevated to 51.52 mM−1s−1, which guided precise photodynamic therapy. This tumor microenvironment-triggered transformable strategy should show great potential for tumor-targeted imaging and phototherapy.

Large T1 contrast enhancement using superparamagnetic nanoparticles in ultra-low field MRI

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely investigated and utilized as magnetic resonance imaging (MRI) contrast and therapy agents due to their large magnetic moments. Local field inhomogeneities caused by these high magnetic moments are used to generate T2 contrast in clinical high-field MRI, resulting in signal loss (darker contrast). Here we present strong T1 contrast enhancement (brighter contrast) from SPIONs (diameters from 11 nm to 22 nm) as observed in the ultra-low field (ULF) MRI at 0.13 mT. We have achieved a high longitudinal relaxivity for 18 nm SPION solutions, r1 = 615 s−1 mM−1, which is two orders of magnitude larger than typical commercial Gd-based T1 contrast agents operating at high fields (1.5 T and 3 T). The significantly enhanced r1 value at ultra-low fields is attributed to the coupling of proton spins with SPION magnetic fluctuations (Brownian and Néel) associated with a low frequency peak in the imaginary part of AC susceptibility (χ”). SPION-based T1-weighted ULF MRI has the advantages of enhanced signal, shorter imaging times, and iron-oxide-based nontoxic biocompatible agents. This approach shows promise to become a functional imaging technique, similar to PET, where low spatial resolution is compensated for by important functional information.

Climate and size correction in European Union's Waste Framework Directive and R1 energy efficiency criteria.

This article presents an analysis on the use of the R1 formula to determine the recovery status of some energy from waste plants. Detailed R1 computations are provided to demonstrate the application of R1 guidelines in incineration and gasification facilities. Climate and size correction methods are proposed in consideration of the disadvantage faced by smaller-sized energy from waste plants or those located in warmer regions in meeting the set threshold. A key highlight is the case-based application of climate and size correction factors to three case study plants in scaling the R1 value in consideration of external variants. The proposed size and climate correction factors are compared with the climate correction factor defined in the Waste Framework Directive of the European Union. The application of the proposed correction factors lead to conservative R1 scaling when compared with the application of the Waste Framework Directive climate correction factor. The introduction of the size correction factor addresses an important gap in the current Waste Framework Directive.

Keratin-Templated Synthesis of Metallic Oxide Nanoparticles as MRI Contrast Agents and Drug Carriers.

Keratin is a family of cysteine-rich structural fibrous proteins abundantly present in skin and skin appendages. Inspired by the template synthesis strategy, in this work, keratin was utilized for the first time as a platform template to synthesize metallic oxide nanoparticles, such as MnO2 (MnNPs@Keratin) and Gd2O3 (GdNPs@Keratin), in a simple and environment-benign fashion. These nanoparticles possess good colloid stability and biocompatibility, high T1 relaxivity ( r1 value = 6.8 mM-1s-1 for MnNPs@Keratin and 7.8 mM-1s-1 for GdNPs@Keratin), and superior in vivo magnetic resonance imaging performance of tumor. Moreover, these keratin-templated nanoparticles have great potential as drug carriers with the capacity of redox-responsive drug release due to the existence of disulfide cross-linking in keratin coating. These results suggest that keratin can be a promising platform template for the development of metal-based nanoparticles for cancer diagnosis and therapy.

Redetermination of the solvent-free crystal structure of l-proline.

The title compound, (S)-pyrrolidine-2-carb-oxy-lic acid (C5H9NO2), commonly known as l-proline, crystallized without the inclusion of any solvent or water mol-ecules through the slow diffusion of diethyl ether into a saturated solution of l-proline in ethanol. l-Proline crystallized in its zwitterionic form and the mol-ecules are linked via N-H⋯O hydrogen bonds, resulting in a two-dimensional network. In comparison to the only other publication of a single-crystal structure of l-proline without inclusions [Kayushina & Vainshtein (1965 ▸). Kristallografiya, 10, 833-844], the R1 value is significantly improved (0.039 versus 0.169) and thus, our data provides higher precision structural information.

On the quality of the continuous rotation electron diffraction data for accurate atomic structure determination of inorganic compounds

The continuous rotation electron diffraction (cRED) method has the capability of providing fast three-dimensional electron diffraction data collection on existing and future transmission electron microscopes; unknown structures could be potentially solved and refined using cRED data collected from nano- and submicrometre-sized crystals. However, structure refinements of cRED data using SHELXL often lead to relatively high R1 values when compared with those refined against single-crystal X-ray diffraction data. It is therefore necessary to analyse the quality of the structural models refined against cRED data. In this work, multiple cRED data sets collected from different crystals of an oxofluoride (FeSeO3F) and a zeolite (ZSM-5) with known structures are used to assess the data consistency and quality and, more importantly, the accuracy of the structural models refined against these data sets. An evaluation of the precision and consistency of the cRED data by examination of the statistics obtained from the data processing software DIALS is presented. It is shown that, despite the high R1 values caused by dynamical scattering and other factors, the refined atomic positions obtained from the cRED data collected for different crystals are consistent with those of the reference models refined against single-crystal X-ray diffraction data. The results serve as a reference for the quality of the cRED data and the achievable accuracy of the structural parameters.

Cyclic RGD‐Coated Ultrasmall Gd2O3 Nanoparticles as Tumor‐Targeting Positive Magnetic Resonance Imaging Contrast Agents

The excellent theranostic properties of gadolinium oxide (Gd2O3) nanoparticles (GNPs) make them very useful as high‐performance positive magnetic resonance imaging (T1 MRI) contrast agents, X‐ray computed tomography (CT) contrast agents, and gadolinium neutron capture therapy (GdNCT) agents in tumor targeting. Among these applications, tumor‐targeting T1 MRI is investigated in this study. To this end, we employ cyclic RGDs (cRGDs; cyclic Arg–Gly–Asp peptides) as tumor‐targeting ligands to coat ultrasmall GNPs (particle diameter = 1.0–2.5 nm). Five types of commercial cRGDs are used in the coating. The cRGD‐coated GNPs (cRGD‐GNPs) are prepared through one‐pot syntheses. They exhibit longitudinal water‐proton relaxivity (r1) values of 10.0–18.7 s–1 mm–1, with r2/r1 ratios of 1.4–1.7 (r2 = transverse water‐proton relaxivity), which are 3–5 times higher than those of commercial Gd chelates. The in vivo tumor targeting of the cRGD‐GNPs is demonstrated by taking T1 MR images in a model mouse with a liver tumor using one of the five cRGD‐GNP sample solutions prepared. Approximately threefold contrast enhancements are observed in the T1 MR images in the tumor region of the liver than in the normal part of the liver, following intravenous administration of the solution. These results demonstrate that cRGD‐GNPs are potential tumor‐targeting T1 MRI contrast agents.

Three-D Mineralogical Mapping of the Kovdor Phoscorite-Carbonatite Complex, NW Russia: III. Pyrochlore Supergroup Minerals

The pyrochlore supergroup minerals (PSM) are typical secondary phases that replace (with zirconolite–laachite) earlier Sc-Nb-rich baddeleyite under the influence of F-bearing hydrothermal solutions, and form individual well-shaped crystals in surrounding carbonatites. Like primary Sc-Nb-rich baddeleyite, the PSM are concentrated in the axial carbonate-rich zone of the phoscorite-carbonatite complex, so their content, grain size and chemical diversity increase from the pipe margins to axis. There are 12 members of the PSM in the phoscorite-carbonatite complex. Fluorine- and oxygen-dominant phases are spread in host silicate rocks and marginal carbonate-poor phoscorite, while hydroxide-dominant PSM occur mainly in the axial carbonate-rich zone of the ore-pipe. Ti-rich PSM (up to oxycalciobetafite) occur in host silicate rocks and calcite carbonatite veins, and Ta-rich phases (up to microlites) are spread in intermediate and axial magnetite-rich phoscorite. In marginal (apatite)-forsterite phoscorite, there are only Ca-dominant PSM, and the rest of the rocks include Ca-, Na- and vacancy-dominant phases. The crystal structures of oxycalciopyrochlore and hydroxynatropyrochlore were refined in the Fd3¯m space group with R1 values of 0.032 and 0.054 respectively. The total difference in scattering parameters of B sites are in agreement with substitution scheme BTi4+ + YOH‒ = BNb5+ + YO2‒. The perspective process flow diagram for rare-metal “anomalous ore” processing includes sulfur-acidic cleaning of baddeleyite concentrate from PSM and zirconolite–laachite impurities followed by deep metal recovery from baddeleyite concentrate and Nb-Ta-Zr-U-Th-rich sulfatic product from its cleaning.

Anchoring Ligand-Effect on Bright Contrast-Enhancing Property of Hollow Mn3O4 Nanoparticle in T1-Weighted Magnetic Resonance Imaging

Here, we describe and conceptualize the influence of surface engineering for hollow manganese oxide nanoparticles (HMONs)-based contrast agents for magnetic resonance imaging (MRI). A systematic study has been conducted for enhancing the relaxivities of HMONs by functionalizing their surface with various capping ligands having different anchoring groups (carboxylate, alcohol, thiol, and amine). Among all studied ligands, carboxylate-anchored ligands exhibit significant increase in magnetization value upon surface capping of HMON. Contrary to the previous hypotheses based on the surface-Mn2+ ions accessibility to water molecules, we proposed surface capping induced magnetization in HMON is responsible for the enhanced relaxivity (r1) value. Further, in vivo imaging efficacy of oleate-capped HMON (OA-HMON) has been demonstrated in mouse brain. This study provides an insightful understanding of contrast enhancement and modulation by surface ligands on manganese oxide-based T1-contrast agents.

Design and characterization of tissue-mimicking gel phantoms for diffusion kurtosis imaging.

The aim of this work was to create tissue-mimicking gel phantoms appropriate for diffusion kurtosis imaging (DKI) for quality assurance, protocol optimization, and sequence development. A range of agar, agarose, and polyvinyl alcohol phantoms with concentrations ranging from 1.0% to 3.5%, 0.5% to 3.0%, and 10% to 20%, respectively, and up to 3g of glass microspheres per 100ml were created. Diffusion coefficients, excess kurtosis values, and relaxation rates were experimentally determined. The kurtosis values for the plain gels ranged from 0.05 with 95% confidence interval (CI) of (0.029,0.071) to 0.216(0.185,0.246), well below the kurtosis values reported in the literature for various tissues. The addition of glass microspheres increased the kurtosis of the gels with values up to 0.523(0.465,0.581) observed for gels with the highest concentration of microspheres. Repeat scans of some of the gels after more than 6 months of storage at room temperature indicate changes in the diffusion parameters of less than 10%. The addition of the glass microspheres reduces the apparent diffusion coefficients (ADCs) and increases the longitudinal and transverse relaxation rates, but the values remain comparable to those for plain gels and tissue, with ADCs observed ranging from 818(585,1053)×10-6 mm2 /s to 2257(2118,2296)×10-6 mm2 /s, R1 values ranging from 0.34(0.32,0.35) 1/s to 0.51(0.50,0.52) 1/s, and R2 values ranging from 9.69(9.34,10.04) 1/s to 33.07(27.10, 39.04) 1/s. Glass microspheres can be used to effectively modify diffusion properties of gel phantoms and achieve a range of kurtosis values comparable to those reported for a variety of tissues.

Biocompatible and pH-sensitive MnO-loaded carbonaceous nanospheres (MnO@CNSs): A theranostic agent for magnetic resonance imaging-guided photothermal therapy

Integrated theranostic agents can provide multifunctional platforms for synergetic cancer diagnosis and therapy. However, the efficiency and safety of agents are of great concern. In this work, we prepared biocompatible and pH-sensitive MnO-loaded carbonaceous nanospheres (MnO@CNSs) for simultaneous magnetic resonance imaging (MRI) and photothermal therapy (PTT). Carbonaceous nanospheres (CNSs) with biocompatibility and unique optical properties were prepared by hydrothermal method for photothermal absorption and released Mn2+ were used for MRI. In vitro the results of MRI T1 relaxivity test showed r1 value in the acidic environment with an increase by 5-fold (from 5.42 mM−1s−1 to 0.18 mM−1s−1), due to excellent pH responsiveness. In addition, MRI and photothermal effect for mouse model showed enhanced T1 signal and temperature elevation in tumor site with photoirradiation. All the aforementioned results embodied that MnO@CNSs can be used as a fine biocompatible and pH-sensitive contrast for combining targeted MRI with accurate photothermal therapy, showing important value and potential in the integration of theranostics of cancer.

Multifunctional hybrid nanoconstruct of zerovalent iron and carbon dots for magnetic resonance angiography and optical imaging: An In vivo study

In magnetic resonance imaging (MRI), gadolinium (Gd) complexes are very often used as contrast agents to enhance the signal from soft tissue deformities and vascular anomalies, to improve the accuracy of diagnosis. The safety concern of using Gd complexes in renally compromised patients pose limitations on its application. To overcome this scenario, we introduce a nontoxic zerovalent iron based nanoparticle as a novel contrast agent for MR angiography and a hybrid version of the same to serve as a dual function contrast agent for targeted liver imaging. The synthesized zerovalent iron (ZVI) nanoparticles after citrate stabilization (C@ZVI) had an average size of 10 nm and exhibited paramagnetic property which is a prerequisite for a positive MRI contrast agent. The longitudinal magnetic relaxivity, r1 of C@ZVI was 4.93 mM−1s−1 which is much higher than that of clinically used Gd based agent, gadoterate meglumine (3.6 mM−1s−1). For multimodal imaging of the liver, initially the ZVI nanoparticle was tailored with a highly liver specific polysaccharide pullulan, and later with fluorescent carbon dots (Cdts) facilitating both optical and MR imaging. The magnetic relaxivity was retained in P@ZVI-Cdts for T1 contrast imaging with an r1 value of 3.48 mM−1s−1. The in vivo MR angiogram using C@ZVI and the liver targeted MRI and optical imaging using P@ZVI-Cdts were successfully demonstrated proving their potential as MRA contrast agent and a liver specific multimodal imaging agent.

Glypican-1-antibody-conjugated Gd-Au nanoclusters for FI/MRI dual-modal targeted detection of pancreatic cancer.

IntroductionPancreatic cancer (PC) has a poor prognosis with high mortality, due to the lack of effective early diagnostic and prognostic tools.Materials and methodsIn order to target and diagnose PC, we developed a dual-modal imaging probe using Glypican-1 (GPC-1) antibody conjugated with Gd–Au nanoclusters (NCs; Gd-Au-NC-GPC-1). GPC-1 is a type of cell surface heparan sulfate proteoglycan, which is often highly expressed in PC. The probe was successfully prepared with a hydrodynamic diameter ranging from 13.5 to 24.4 nm.ResultsSpectral characteristics showed absorption at 280 nm and prominent emission at 650 nm. Confocal microscopic imaging showed effective detection of GPC-1 highly expressed PC cells by Gd-Au-NC-GPC-1, which was consistent with flow cytometry results. In vitro relaxivity characterization demonstrated that the r1 value of the probe was 17.722 s−1 mM−1 Gd, which was almost 4 times higher compared with that of Gd-diethylenetriaminepentacetate (DTPA; r1 value =4.6 s−1 mM−1 Gd). Gd-Au-NC-GPC-1 exhibited similar magnetic resonance (MR) signals when compared to Gd-DTPA even at lower Gd concentrations. Much higher MR signals were registered in PC cells (COLO-357) compared with normal cells (293T). Furthermore, Gd-Au-NC-GPC-1 could effectively detect PC cells in vivo by dual-modal fluorescence imaging/magnetic resonance imaging (FI/MRI) at 30 minutes postinjection. In addition, Gd-Au-NC-GPC-1 did not show significant biotoxicity to normal cells at tested concentrations both in vitro and in vivo.ConclusionGd-Au-NC-GPC-1 has demonstrated to be a promising dual-modal FI/MRI contrast agent for targeted diagnosis of PC.

Low Cost Humidity Sensor Based on PANI/PEDOT:PSS Printed on Paper

The production of low cost sensors to monitor environment in some industrial sectors is a current need. In aviculture centers, for example, the concentration of ammonia gas is related to humidity, and it is necessary to control it to avoid contamination. With this need in mind, this paper presents the preparation and characterization of a low cost humidity sensor based on poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) and polyaniline fully printed onto paper by a commercial HP printer. Using electrochemical impedance spectroscopy, an equivalent circuit containing resistive and capacitive parameters was proposed. The resistive parameter R1 is related to values of ambient humidity. The R1 values showed a sensitive response of 200% when relative humidity changes 80%, taking 10 min to reach saturation point. Moreover, the device showed good stability when humidity remained constant. These results indicate that the proposed device is suitable for applying as a humidity sensor that costs less than 1 Euro cent.

Molecular imaging of myocardial infarction with Gadofluorine P – A combined magnetic resonance and mass spectrometry imaging approach

BackgroundMolecular MRI is becoming increasingly important for preclinical research. Validation of targeted gadolinium probes in tissue however has been cumbersome up to now. Novel methodology to assess gadolinium distribution in tissue after in vivo application is therefore needed. PurposeTo establish combined Magnetic Resonance Imaging (MRI) and Mass Spectrometry Imaging (MSI) for improved detection and quantification of Gadofluorine P deposition in scar formation and myocardial remodeling. Materials and methodsAnimal studies were performed according to institutionally approved protocols. Myocardial infarction was induced by permanent ligation of the left ascending artery (LAD) in C57BL/6J mice. MRI was performed at 7T at 1 week and 6 weeks after myocardial infarction. Gadofluorine P was used for dynamic T1 mapping of extracellular matrix synthesis during myocardial healing and compared to Gd-DTPA. After in vivo imaging contrast agent concentration as well as distribution in tissue were validated and quantified by spatially resolved Matrix-Assisted Laser Desorption Ionization (MALDI) MSI and Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry (LA-ICP-MS) imaging. ResultsBoth Gadofluorine P enhancement as well as local tissue content in the myocardial scar were highest at 15 minutes post injection. R1 values increased from 1 to 6 weeks after MI (1.62 s−1 vs 2.68 s−1, p = 0.059) paralleled by an increase in Gadofluorine P concentration in the infarct from 0.019 mM at 1 week to 0.028 mM at 6 weeks (p = 0.048), whereas Gd-DTPA enhancement showed no differences (3.95 s−1 vs 3.47 s−1, p = 0.701). MALDI-MSI results were corroborated by elemental LA-ICP-MS of Gadolinium in healthy and infarcted myocardium. Histology confirmed increased extracellular matrix synthesis at 6 weeks compared to 1 week. ConclusionAdding quantitative MSI to MR imaging enables a quantitative validation of Gadofluorine P distribution in the heart after MI for molecular imaging.

Porous GdAlO3: Cr3+, Sm3+ drug carrier for real-time long afterglow and magnetic resonance dual-mode imaging

Here, a kind of porous nanoparticles GdAlO3:Cr3+, Sm3+ (GAO:Cr,Sm) which own magnetic resonance and long persistent luminescent properties have been synthesized. The spherical morphology and narrow size distribution would allow the GAO:Cr,Sm nanoparticles to be utilised as a drug carrier and the drug release results indicate that the GAO:Cr,Sm drug carriers have an excellent drug sustained properties. Applying the Cr3+ and Sm3+ coped with gadolinium aluminate as the NIR persistent luminescence center and the energy transfer resonance from Gd3+ to Cr3+, these nanoparticles exhibit excellent NIR persistent luminescence at 732 nm under the UV irradiation of 254 nm and it can persist for about half an hour. In addition, they possess a longitudinal relaxivity (r1) value of 4.75 mM−1 s−1, which means that these nanoparticles could be applied for MR imaging as contrast agents. Carboxymethyl Chitosan was modified on the surface of GAO:Cr,Sm nanoparticles to make them owning excellent biocompatibility and low toxicity and these nanoparticles were successful to realize in vivo imaging. Hence, the well-defined nanoprobes of GAO:Cr,Sm exhibit great potential in biomedicine as trackable drug carriers and in vivo imaging agent due to the dual-model imaging property.

Oxy-dravite from Wołowa Góra Mountain, Karkonosze massif, SW Poland: Crystallochemical and structural studies

ABSTRACTYellowish dravitic tourmaline (dominated by the oxy-dravite component) associated with secondary fluor-dravite/fluor-schorl and dravite/schorl tourmalines was found in a quartz vein cropping out in the eastern part of the Karkonosze Mountains range, SW Poland. The crystal structure of this tourmaline was refined to an R1 value of 1.85% based on single-crystal data, and the chemical composition was determined by electron-microprobe analysis. The tourmaline, a representative of the alkali-tourmaline group, has the structural formula: (Na0.75Ca0.12□0.13)Σ1(Mg1.93Al0.95Ti0.06${\rm Fe}_{{\rm 0}{\rm. 04}}^{{\rm 2 +}} $ V0.01)Σ3(Al5.38Mg0.62)Σ6B3Si6O27(OH)3(O0.46OH0.33F0.21)Σ1, and is characterized by an extremely high Mg/(Mg + Fe) ratio of 0.97–0.99, the WO2– content that reaches 0.59 apfu resulting in a local predominance of the oxy-dravitic component and Mg–Al disorder on the octahedral Y and Z sites of the order of 0.64 apfu. This disordering results in an increasing <Z–O> distance with ~1.925 Å, and unit-cell parameters a = 15.916(1) Å and c = 7.180(1) Å. The tourmaline formed during Variscan prograde metamorphism under the influence of a released (H2O,B,F)-bearing fluid. The fluid mobilized the most soluble components of partly altered silicic volcaniclastic material of the Late Cambrian to Early Ordovician bimodal volcanism to become the protolith for adjacent quartzo-feldspathic schists and amphibolites, and propagated them into the surrounding granitic gneisses of the Kowary unit in the eastern metamorphic cover of the Karkonosze granite.