Toward quantification of hypoxia using fluorinated EuII/III-containing ratiometric probes.

Hypoxia is a prognostic biomarker of rapidly growing cancers, where the extent of hypoxia is an indication of tumor progression and prognosis; therefore, hypoxia is also used for staging while performing chemo- and radiotherapeutics for cancer. Contrast-enhanced MRI using EuII-based contrast agents is a noninvasive method that can be used to map hypoxic tumors, but quantification of hypoxia using these agents is challenging due to the dependence of signal on the concentration of both oxygen and EuII. Here, we report a ratiometric method to eliminate concentration dependence of contrast enhancement of hypoxia using fluorinated EuII/III-containing probes. We studied three different EuII/III couples of complexes containing 4, 12, or 24 fluorine atoms to balance fluorine signal-to-noise ratio with aqueous solubility. The ratio between the longitudinal relaxation time (T1) and 19F signal of solutions containing different ratios of EuII- and EuIII-containing complexes was plotted against the percentage of EuII-containing complexes in solution. We denote the slope of the resulting curves as hypoxia indices because they can be used to quantify signal enhancement from Eu, that is related to oxygen concentration, without knowledge of the absolute concentration of Eu. This mapping of hypoxia was demonstrated in vivo in an orthotopic syngeneic tumor model. Our studies significantly contribute toward improving the ability to radiographically map and quantify hypoxia in real time, which is critical to the study of cancer and a wide range of diseases.

Expanding the Coordination of f-Block Metals with Tris[2-(2-methoxyethoxy)ethyl]amine: From Molecular Complexes to Cage-like Structures.

Low-valent f-block metals have intrinsic luminescence, electrochemical, and magnetic properties that are modulated with ligands, causing the coordination chemistry of these metals to be imperative to generating critical insights needed to impact modern applications. To this end, we synthesized and characterized a series of twenty-seven complexes of f-metal ions including EuII, YbII, SmII, and UIII and hexanuclear clusters of LaIII and CeIII to study the impact of tris[2-(2-methoxyethoxy)ethyl]amine, a flexible acyclic analogue of the extensively studied 2.2.2-cryptand, on the coordination chemistry and photophysical properties of low-valent f-block metals. We demonstrate that the flexibility of the ligand enables luminescence tunability over a greater range than analogous cryptates of EuII in solution. Furthermore, the ligand also displays a variety of binding modes to f-block metals in the solid state that are inaccessible to cryptates of low-valent f-block metals. In addition to serving as a ligand for f-block metals of various sizes and oxidation states, tris[2-(2-methoxyethoxy)ethyl]amine also deprotonates water molecules coordinated to trivalent triflate salts of f-block metal ions, enabling the isolation of hexanuclear clusters containing either LaIII or CeIII. The ligand was also found to bind more tightly to YbII and UIII in the solid state compared to 2.2.2-cryptand, suggesting that it can play a role in the isolation of other low-valent f-block metals such CfII, NpIII, and PuIII. We expect that our findings will inspire applications of tris[2-(2-methoxyethoxy)ethyl]amine in the design of light-emitting diodes and the synthesis of extremely reducing divalent f-block metal complexes that are of interest for a wide range of applications.

3D-printed, patient-specific cutting guides improve femoral and tibial cut alignment in canine total knee replacement.

OBJECTIVES: The purpose of this cadaveric study was to determine whether patient-specific guides (PSGs) improve the accuracy of tibial and femoral cut alignment in canine total knee replacement (TKR), as compared with generic cutting guides. STUDY DESIGN: Original research. ANIMALS: Sixteen pelvic limbs from skeletally mature medium- to large-breed canine cadavers. METHODS: Specimens were randomly allocated to one of two groups (PSG or Generic; N = 8/group). In the Generic group, femoral and tibial ostectomies were made using the standard canine TKR femoral cutting blocks and tibial alignment guide. In the PSG group, the cuts were made using a series of custom 3D-printed cutting guides. "Planned" and "actual" tibial and femoral cut alignments were compared in the frontal and sagittal planes, and errors were calculated by subtracting actual from planned values. RESULTS: Use of 3D-printed PSGs improved tibial cut alignment in the frontal plane but not the sagittal plane. PSGs also improved the alignment of the cranial and distal femoral ostectomies but did not impact varus-valgus alignment. CONCLUSIONS: These findings support the use of PSGs for TKR in dogs. Clinical trials are now needed to determine whether the benefits of PSGs translate into measurable improvements in joint function and implant longevity. CLINICAL SIGNIFICANCE: PSGs have the potential to improve femoral and tibial component alignment in canine TKR.

Systemic Delivery of Divalent Europium from Ligand Screening with Implications to Direct Imaging of Hypoxia.

Hypoxia is a hallmark of many diseases, including cancer, arthritis, heart and kidney diseases, and diabetes, and it is often associated with disease aggressiveness and poor prognosis. Consequently, there is a critical need for imaging hypoxia in a noninvasive and direct way to diagnose, stage, and monitor the treatment and development of new therapies for these diseases. Eu-containing contrast agents for magnetic resonance imaging have demonstrated potential for in vivo imaging of hypoxia via changes in metal oxidation state from +2 to +3, but rapid oxidation in blood limits EuII-containing complexes to studies compatible with direct injection to sites. Here, we report a new EuII-containing complex that persists in oxygenated environments and is capable of persisting in blood long enough for imaging by magnetic resonance imaging. We describe the screening of a library of ligands that led to the discovery of the complex as well as a pH-dependent mechanism that hinders oxidation to enable usefulness in vivo. These studies of the first divalent lanthanide complex that persists in oxygenated solutions open the door to the use of EuII-based contrast agents for imaging hypoxia in a wide range of diseases.

Near-Infrared Lanthanide-Based Emission from Fused Bis[Ln(III)/Zn(II) 14-metallacrown-5] Coordination Compounds.

A set of (Ln[14-MCZn(II)N(quinHA)-5])2Ln2Zn2(quinHA)2(ph)2(Hph)4(OH)8(H2O)4 metallacrowns (Ln-1, Ln = Tb, Gd, or Yb; H2quinHA = quinaldic hydroxamic acid, H2ph = phthalic acid) have been synthesized via solution-state self-assembly. The metallacrowns possess an uncommon topology within the metallacrown family where two rarely seen 14-metallacrown-5 moieties are fused by a Yb2Zn2(quinHA)2 bridge. Moreover, Yb-1 analyzed in the solid state exhibits a characteristic near-infrared luminescence signal arising from Yb3+ 2F5/2→2F7/2 transition despite the proximity of high energy O-H oscillators.

Development of a Highly Selective Ni(II) Chelator in Aqueous Solution.

The design, synthesis, and characterization of a novel Ni(II) chelator SG-20 is reported. SG-20 is selective in binding to Ni(II) versus other metal ions including Cu(II), Fe(II), Co(II), and Zn(II). At pH = 7.1, SG-20 binds Ni(II) with a Kd = 7.0 ± 0.4 µM. Job analysis indicates that SG-20 binds to both Ni(II) and Cu(II) with a 1:1 stoichiometry. Affinity of SG-20 for Ni(II) is pH dependent and decreases upon lowering to pH 4.0. A green solid was isolated from the reaction of SG-20 with NiCl2·6H2O in MeOH and characterized by X-ray photoelectron spectroscopy (XPS), electronic absorption and infrared (IR) spectroscopies, and mass spectrometry. Collectively, XPS and IR analysis revealed Ni-N and Ni-O interactions and a shift in C-O asymmetric and symmetric stretches consistent with Ni binding. Attempts to crystalize a mononuclear complex were unsuccessful, likely due to the Ni-SG-20 complex being in equilibrium with higher order species in solution. However, reaction of SG-20 with NiCl2·6H2O in water followed by slow evaporation yielded green crystals that were characterized by electronic absorption spectroscopy (λmax = 260 nm) and X-ray crystallography. These analyses revealed that SG-20 supports formation of a complex cluster containing six SG-20 ligands, 15 Ni(II), and three Na(I) centers, with two distinct types of Ni atoms in its outer and inner core. The nine Ni atoms present in the inner core were bound by oxo and carbonate bridges, whereas the six Ni atoms present in its outer shell were bound to N, O, and S donor atoms derived from SG-20. Overall, X-ray crystallographic analysis revealed that two chelator arms of SG-20 bind to one Ni(II) ion with an axial aqua ligand, whereas the third arm is free to interact with Ni ions within the central cluster, supporting the goal of Ni capture.

Properties of Amine-Containing Ligands That Are Necessary for Visible-Light-Promoted Catalysis with Divalent Europium.

We describe a study of the influence of amine-containing ligands on the photoredox-relevant properties of EuII toward the rational design of EuII-containing catalysts for visible-light-promoted photoredox reactions. We report our observations of the effects of the degree of functionalization of amines, denticity, and macrocylic ligands on the absorbance of EuII. Ligands that contain secondary amines bathochromically shift the absorbance of EuCl2 relative to ligands that contain primary or tertiary amines. Similarly, ligands of larger denticity have a larger bathochromic shift of the absorbance than ligands of smaller denticity. We observed that macrocyclic ligands have a larger effect on the absorbance of EuCl2 than nonmacrocyclic ligands. Also, we report the photoredox reactivity of four new EuII-containing complexes. These observations are potentially influential in understanding the ligand properties that promote the use of EuII in visible-light-promoted photoredox catalysis.

Owner-reported outcome measures in veterinary care for companion animal orthopedic patients: An international online survey of veterinarians' expectations and practices.

OBJECTIVE: To report veterinarians' familiarity with and perceptions of owner/observer-reported outcome measures (OROMs) and their applications in routine clinical practice. STUDY DESIGN: Cross-sectional online survey. ANIMALS OR SAMPLE POPULATION: A total of 441 veterinarians with a caseload of companion animal orthopedic patients. METHODS: Respondents answered questions regarding their familiarity with and application of OROMs. Respondents provided opinions on statements related to reasons for using or not using OROMs in routine clinical practice, prerequisites to implement OROMs in routine clinical practice, and whether they would implement OROMs in routine clinical practice if adequate tools/technologies were available. RESULTS: Most (293/441, 66.4%) respondents felt familiarity with at least one OROM. Only 17.5% (77 out of the 440 answering the question about the application of OROMs) applied OROMs in routine clinical practice. The two main reasons for not using OROMs in routine clinical practice were the lack of opportunity/feasibility and the lack sufficient information/knowledge/experiences. User-friendliness, time efficiency, and interpretability were considered the most important prerequisites for implementing OROMs in routine clinical practice. If adequate tools/technologies were available, 266/439 (60.6%) respondents indicated that they would definitely implement OROMs in routine clinical practice. CONCLUSION: Although most respondents were familiar with at least one OROM, fewer than one-fifth applied them in routine clinical practice. Most respondents were willing to implement OROMs in routine clinical practice if adequate tools/technologies were available. CLINICAL SIGNIFICANCE: Our results justify further investigations to improve the application of OROMs in routine clinical practice in veterinary care of companion animal orthopedic patients.

Rational Design of High-Relaxivity EuII -Based Contrast Agents for Magnetic Resonance Imaging of Low-Oxygen Environments.

Metal-based contrast agents for magnetic resonance imaging present a promising avenue to image hypoxia. EuII -based contrast agents have a unique biologically relevant redox couple, EuII/III , that distinguishes this metal for use in hypoxia imaging. To that end, we investigated a strategy to enhance the contrast-enhancing capabilities of EuII -based cryptates in magnetic resonance imaging by controlling the rotational dynamics. Two dimetallic, EuII -containing cryptates were synthesized to test the efficacy of rigid versus flexible coupling strategies. A flexible strategy to dimerization led to a modest (114 %) increase in contrast enhancement per Eu ion (60 MHz, 298 K), but a rigid linking strategy led to an excellent (186 %) increase in contrast enhancement despite this compound's having the smaller molecular mass of the two dimetallic complexes. We envision the rigid linking strategy to be useful in the future design of potent EuII -based contrast agents for magnetic resonance imaging.

Versatile Para-Substituted Pyridine Lanthanide Coordination Complexes Allow Late Stage Tailoring of Complex Function.

A series of cationic and neutral p-Br and p-NO2 pyridine substituted Eu(III) and Gd(III) coordination complexes serve as versatile synthetic intermediates. Nucleophilic aromatic substitution occurs readily at the para position under mild conditions, allowing C-N and C-C bond forming reactions to take place, permitting the introduction of azide, amino and alkynyl substituents. For Eu(III) complexes, this approach allows late stage tuning of absorption and emission spectral properties, exemplified by the lowering of the energy of an LMCT transition accompanied by a reduction in the Eu-Npy bond length. Additionally, these complexes provide direct access to the corresponding Eu(II) analogues. With the Gd(III) series, the nature of the p-substituent does not significantly change the EPR properties (linewidth, relaxation times), as required for their development as EPR spin probes that can be readily conjugated to biomolecules under mild conditions.

The effect of plate fixation on supination and pronation of the feline antebrachium: a model of pancarpal arthrodesis.

BACKGROUND: Pancarpal arthrodesis is purported to limit supination and pronation of the feline antebrachium. The objective of this study was to investigate whether plate fixation of the radius to the carpus and metacarpus limits supination and pronation of the ulna relative to the radius as a model for pancarpal arthrodesis in the cat. Eight feline cadaveric forelimbs were rotated from supination to pronation in a testing jig and CT (computed tomography) was performed in the neutral, supinated and pronated positions. A locking plate was then secured dorsally to the radius, radial carpal bone and metacarpal III of each of the limbs. CT was repeated in each of the testing positions following plate application. The radius and ulna of the control specimens, and the radius, ulna and plate of the plated specimens were then segmented using software. Alignment of the bones to the radius in the control specimens, and to the plate in the plated specimens was used to compare the changes in degrees of movement of the ulna relative to the radius in dorsal, sagittal and transverse planes. RESULTS: Based on the results of the paired t test, there was no significant difference in degrees of movement, or total range of motion between control and plated specimens in supinated and pronated testing conditions. CONCLUSION: The results of this ex-vivo study indicate that under the testing conditions employed, plate fixation of the radius to the carpus and metacarpus does not limit supination and pronation of the feline antebrachium.

Systematic Tuning of the Optical Properties of Discrete Complexes of EuII in Solution Using Counterions and Solvents.

We describe a systematic study of the influence of halides and solvents on the optical properties of EuII-containing complexes in solution starting from well-defined crystalline precursors. Anionic halides, chloride and bromide, blue-shift the spectroscopic properties of EuII, whereas neutral ligands, methanol and acetonitrile, cause a red shift. This system provides evidence that EuII has a stronger affinity for chloride, and to some extent bromide, relative to acetonitrile but not methanol. We also describe a simple procedure using an ion-exchange resin for the exchange of iodide counterions to hexafluorophosphate. These findings are a step toward designing ligands that can tune the optical properties of EuII-containing complexes for solution-based applications.

Measurement of the Dissociation of EuII-Containing Cryptates Using Murexide.

The dissociation rates of five EuII-containing cryptates in water were measured using UV-visible spectroscopy and murexide at pH 6.5, 7, 7.5, 8, and 9. Murexide was used as a coordinating dye for EuII. The results for a known cryptate were within experimental error of the value obtained using other methods and enabled the measurement of other cryptates. This validation of the use of murexide to study the dissociation of EuII-containing cryptates enables its use with other complexes of EuII.

Spectroscopic and Electrochemical Trends in Divalent Lanthanides through Modulation of Coordination Environment.

Due to the importance of both visible-light luminescence and lanthanides in modern society, the influence of the ligand environment on complexes of YbII were studied and compared with analogous complexes of EuII. Four ligands with systematically varied electronic and steric characteristics were used to probe the coordination environment and electronic and redox properties of the corresponding YbII-containing complexes. Strong-field nitrogenous donors gave rise to bathochromic shifts, leading to visible-light absorption by YbII. Trends in properties across the series of YbII-containing complexes were compared to trends reported for the analogous EuII-containing complexes, revealing the translatability of coordination environment effects across the divalent lanthanide series. These studies provide valuable information regarding the behavior of small and medium-sized divalent lanthanides outside of the solid state.

Lanthanide Luminescence in Visible-Light-Promoted Photochemical Reactions.

The excitation of lanthanides with visible light to promote photochemical reactions has garnered interest in recent years. Lanthanides serve as initiators for photochemical reactions because they exhibit visible-light-promoted 4f→5d transitions that lead to emissive states with electrochemical potentials that are more negative than the corresponding ground states. The lanthanides that have shown the most promising characteristics for visible-light promoted photoredox are SmII, EuII, and CeIII. By understanding the effects that ligands have on the 5d orbitals of SmII, EuII, and CeIII, luminescence and reactivity can be rationally modulated using coordination chemistry. This review briefly overviews the photochemical reactivity of SmII, EuII, and CeIII with visible light; the properties that influence the reactivity of these ions; and the research that has been reported towards modulating their photochemical-relevant properties using visible light and coordination chemistry.

DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS IN CAPTIVE GORILLAS (GORILLA SPP.): APPEARANCES AND DIAGNOSIS.

Diffuse idiopathic skeletal hyperostosis (DISH) is a disorder of unknown cause, in which new bone forms in soft tissues attached to the skeleton. Originally described in humans, in whom it is quite common, it is usually asymptomatic. New bone may completely bridge across joints, especially in the spine. However, it can be difficult to distinguish from diseases such as spondyloarthritis and spondylosis. With safer and increased use of radiography in diagnosis, the unfamiliar skeletal changes of asymptomatic DISH may now be coincidentally revealed during investigation of other disorders and result in misdiagnosis and unnecessary treatment. There have been case reports of its occurrence in great apes, but this is the first study to illustrate its appearances in a series of 11 skeletons of western and eastern lowland gorillas (Gorilla gorilla gorilla and Gorilla beringei graueri) from zoos in Europe and the United States. The study combines a review of available clinical and postmortem records with examination of the skeletons and radiologic investigation, such as computed tomography (CT). The results indicate that the disorder is probably common in older (>30 yr) captive gorillas, but that it is asymptomatic. It was not symptomatic during life in any of these animals. Several cases had unexpected features, such as extensive involvement of the thorax and extra-articular sacroiliac and tibiofibular joint fusions that are not typical in humans. By illustrating these skeletons, the study should aid differentiation of DISH from spondylosis (syn spondylosis deformans) and spondyloarhritis. It illustrates those features that are atypical of human DISH. CT scanning is valuable in such cases for examining diagnostically important areas such as sacroiliac joints. Increased awareness of DISH should help with understanding its cause, both in gorillas and humans.

Screening of ligands for redox-active europium using magnetic resonance imaging.

We report a screening procedure to predict ligand coordination to EuII and EuIII using magnetic resonance imaging in which bright images indicate complexation and dark images indicate no complexation. Here, paramagnetic GdIII is used as a surrogate for EuIII in the screening procedure to enable detection with magnetic resonance imaging. The screening procedure was tested using a set of eight ligands with known coordination to EuII and EuIII, and results were found to be consistent with expected binding. Validation of the screening procedure with known coordination chemistry enables use with new ligands in the future.

Molecular dynamics investigation of water-exchange reactions on lanthanide ions in water/1-ethyl-3-methylimidazolium trifluoromethylsufate ([EMIm][OTf]).

We report a kinetic study of the water exchange on lanthanide ions in water/[1-ethyl-3-methylimidazolium][trifluoromethylsufate] (water/[EMIm][OTf]). The results from 17O-NMR measurements show that the water-exchange rates in water/[EMIm][OTf] increase with decreasing size of the lanthanide ions. This trend for water-exchange is similar to the previously reported trend in water/1-ethyl-3-methylimidazolium ethyl sulfate (water/[EMIm][EtSO4]) but opposite to that in water. To gain atomic-level insight into these water-exchange reactions, molecular dynamics simulations for lanthanide ions in water/[EMIm][OTf] have been performed using the atomic-multipole-optimized-energetics-for-biomolecular-application polarizable force field. Our molecular dynamics simulations reproduce the experimental water-exchange rates in terms of the trend and provide possible explanations for the observed experimental behavior. The smaller lanthanide ions in water/[EMIm][OTf] undergo faster water exchange because the smaller lanthanide ions coordinate to the first shell [OTf]- anions more tightly, resulting in a stronger screening effect for the second-shell water. The screening effect weakens the interaction of the lanthanide ions with the second-shell water molecules, facilitating the dissociation of water from the second-shell and subsequent association of water molecules from the outer solvation shells.

Kinematic behavior of a novel pedicle screw-rod fixation system for the canine lumbosacral joint.

OBJECTIVE: To determine the biomechanical behavior of a novel distraction-stabilization system, consisting of an intervertebral distraction bolt, polyaxial screws, and connecting rods, in the canine lumbosacral spine. STUDY DESIGN: Biomechanical study. SAMPLE POPULATION: Cadaveric canine lumbosacral spines (L4-Cd3) (N = 8). METHODS: Cadaveric lumbosacral spines were harvested, stripped of musculature, mounted on a 4-point bending jig, and tested in extension, flexion, and lateral bending using nondestructive compressive axial loads (0-150 N). Angular displacement was recorded from reflective optical trackers rigidly secured to L6, L7, and S1. Data for primary and coupled motion were collected from intact spines, after destabilization at L7-S1, and following surgical stabilization with the new implant system. RESULTS: As compared with the intact spine, laminectomy resulted in a modest increase in angular displacement at L6-L7 and a marked increase at L7-S1. Instrumentation significantly reduced motion at the operated level (L7-S1) with a concomitant increase at the adjacent level (L6-L7). CONCLUSION: The combination of a polyaxial pedicle screw-rod system and intervertebral spacer provides a versatile solution of surgical stabilization of the lumbosacral joint following surgical decompression in the canine lumbosacral spine. The increase in motion at L6-L7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this question. CLINICAL RELEVANCE: These results support the feasibility of using this new implant system for the management of degenerative lumbosacral disease in dogs. The increase in motion at L6-L7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this question.

The Role of Coordination Environment and pH in Tuning the Oxidation Rate of Europium(II).

The EuII/III redox couple offers metal-based oxidation-sensing with magnetic resonance imaging making the study of EuII oxidation chemistry important in the design of new probes. Accordingly, we explored oxidation reactions with a set of EuII -containing complexes. Superoxide formation from the reaction between EuII and dioxygen was observed using electron paramagnetic resonance spectroscopy. Additionally, oxidation kinetics of three EuII -containing complexes with bromate and glutathione disulfide at pH values, including 5 and 7, is reported. In the reaction with bromate, the oxidation rate of two of the complexes increased by 7.3 and 6.7 times upon decreasing pH from 7 to 5, but the rate increased by 17 times for a complex containing amide functional groups over the same pH range. The oxidation rate of a fluorobenzo-functionalized cryptate was relatively slow, indicating that the ligand used to impart thermodynamic oxidative stability might also be useful for controlling oxidation kinetics.