Two Beta-Phosphorylamide Compounds as Ligands for Sm3+, Eu3+, and Tb3+: X-ray Crystallography and Luminescence Properties.

This paper describes the synthesis of two beta-phosphorylamide ligands and their coordination chemistry with the Ln ions Tb3+, Eu3+, and Sm3+. Both the ligands and Ln complexes were characterized by IR, NMR, MS, and X-ray crystallography. The luminescence properties of the Tb3+ and Eu3+ complexes were also characterized, including the acquisition of lifetime decay curves. In the solid state, the Tb3+ and Sm3+ ligand complexes were found to have a 2:2 stoichiometry when analyzed by X-ray diffraction. In these structures, the Ln ion was bound by both oxygen atoms of each beta-phosphorylamide moiety of the ligands. The Tb3+ and Eu3+ complexes were modestly emissive as solutions in acetonitrile, with lifetime values that fell within typical ranges.

Mucosal barrier injury-associated bloodstream infections in pediatric oncology patients.

BACKGROUND: Single-center reports of central line-associated bloodstream infection (CLABSI) and the subcategory of mucosal barrier injury laboratory-confirmed bloodstream infection (MBI-LCBI) in pediatric hematology oncology transplant (PHO) patients have focused on the inpatient setting. Characterization of MBI-LCBI across PHO centers and management settings (inpatient and ambulatory) is urgently needed to inform surveillance and prevention strategies. METHODS: Prospectively collected data from August 1, 2013, to December 31, 2015, on CLABSI (including MBI-LCBI) from a US PHO multicenter quality improvement network database was analyzed. CDC National Healthcare Safety Network definitions were applied for inpatient events and adapted for ambulatory events. RESULTS: Thirty-five PHO centers reported 401 ambulatory and 416 inpatient MBI-LCBI events. Ambulatory and inpatient MBI-LCBI rates were 0.085 and 1.01 per 1000 line days, respectively. Fifty-three percent of inpatient CLABSIs were MBI-LCBIs versus 32% in the ambulatory setting (P  <  0.01). Neutropenia was the most common criterion defining MBI-LCBI in both settings, being present in ≥90% of events. The most common organisms isolated in MBI-LCBI events were Escherichia coli (in 28% of events), Klebsiella spp. (23%), and viridans streptococci (12%) in the ambulatory setting and viridans streptococci (in 29% of events), E. coli (14%), and Klebsiella spp. (14%) in the inpatient setting. CONCLUSION: In this largest study of PHO MBI-LCBI inpatient events and the first such study in the ambulatory setting, the burden of MBI-LCBI across the continuum of care of PHO patients was substantial. These data should raise awareness of MBI-LCBI among healthcare providers for PHO patients, help benchmarking across centers, and help inform prevention and treatment strategies.

Lanthanide extraction selectivity of a tripodal carbamoylmethylphosphine oxide ligand system.

Four tripodal carbamoylmethylphosphine oxide (CMPO)-based ligands are reported here and assessed with regard to lanthanide (Ln) coordination chemistry and selective extraction of lanthanide ions from aqueous solution. Inspired by previous liquid-liquid extraction studies that suggested a preference for terbium(iii), the current work further probes the extraction behavior of a tris-(2-aminoethyl)amine (TREN) capped, ethoxy substituted CMPO ligand with respect to the entire series of lanthanides. Upon confirmation of Tb3+ extraction selectivity versus the whole series, experiments were conducted to assess the effect of increasing the alkyl chain length within the ligand TREN cap, as well as changing the CMPO substituents by replacing the ethoxy groups with more hydrophobic phenyl groups to promote solubility in the organic extraction solvent. Extraction efficiencies remained low for most lanthanides upon increasing the cap size, with %E values consistently around 5%, and a complete loss of Tb3+ preference was noted with a decrease in %E from 18% to 3.5%. For the agent employing the original, smaller TREN cap but with phenyl substituents on the CMPO units, an increase in extraction toward the middle of the row was again observed, albeit modest, with relatively high %E values for both Gd3+ and Tb3+versus the other lanthanides (13 and 11%, respectively). A more dramatic extraction selectivity for the phenyl substituted ligand was achieved upon modification of the ligand to metal ratio, with a 100 : 1 ratio resulting in a near linear decrease in %E from 41% for La3+ to 3.7% for Lu3+. Finally, modification of the TREN capping scaffold by adding an oxygen atom to the central nitrogen led to consistently low %E values, revealing the effect of TREN cap oxidation on Ln extraction for this tripodal CMPO ligand system.

X-ray crystallographic, luminescence and NMR studies of phenacyldiphenylphosphine oxide with the Ln(iii) ions Sm, Eu, Gd, Tb and Dy.

We report here the characterization in solution (NMR, luminescence, MS) and the solid-state (X-ray crystallography, IR) of complexes between phenacyldiphenylphosphine oxide and five Ln(iii) ions (Sm, Eu, Gd, Tb, Dy). Four single crystal X-ray structures are described here showing a 1 : 2 ratio between the Ln3+ ions Eu, Dy, Sm and Gd and the ligand, where the phosphine oxide ligands are bound in a monodentate manner to the metal center. A fifth structure is reported for the 1 : 2 Eu(NO3)3-ligand complex showing bidentate binding between the two ligands and the metal center. The solution coordination chemistry of these metal complexes was probed by 1H, 13C and 31P NMR, mass spectrometry, and luminescence experiments. The title ligand has the capability to sensitize Tb3+, Dy3+, Eu3+ and Sm3+ leading to metal-centered emission in solutions of acetonitrile and methanol and in the solid state.

A Prospective, Holistic, Multicenter Approach to Tracking and Understanding Bloodstream Infections in Pediatric Hematology-Oncology Patients.

OBJECTIVE To assess the burden of bloodstream infections (BSIs) among pediatric hematology-oncology (PHO) inpatients, to propose a comprehensive, all-BSI tracking approach, and to discuss how such an approach helps better inform within-center and across-center differences in CLABSI rate DESIGN Prospective cohort study SETTING US multicenter, quality-improvement, BSI prevention network PARTICIPANTS PHO centers across the United States who agreed to follow a standardized central-line-maintenance care bundle and track all BSI events and central-line days every month. METHODS Infections were categorized as CLABSI (stratified by mucosal barrier injury-related, laboratory-confirmed BSI [MBI-LCBI] versus non-MBI-LCBI) and secondary BSI, using National Healthcare Safety Network (NHSN) definitions. Single positive blood cultures (SPBCs) with NHSN defined common commensals were also tracked. RESULTS Between 2013 and 2015, 34 PHO centers reported 1,110 BSIs. Among them, 708 (63.8%) were CLABSIs, 170 (15.3%) were secondary BSIs, and 232 (20.9%) were SPBCs. Most SPBCs (75%) occurred in patients with profound neutropenia; 22% of SPBCs were viridans group streptococci. Among the CLABSIs, 51% were MBI-LCBI. Excluding SPBCs, CLABSI rates were higher (88% vs 77%) and secondary BSI rates were lower (12% vs 23%) after the NHSN updated the definition of secondary BSI (P<.001). Preliminary analyses showed across-center differences in CLABSI versus secondary BSI and between SPBC and CLABSI versus non-CLABSI rates. CONCLUSIONS Tracking all BSIs, not just CLABSIs in PHO patients, is a patient-centered, clinically relevant approach that could help better assess across-center and within-center differences in infection rates, including CLABSI. This approach enables informed decision making by healthcare providers, payors, and the public. Infect Control Hosp Epidemiol 2017;38:690-696.

Turning on lanthanide luminescence via nanoencapsulation.

Encapsulation of macrocyclic europium(III) chelates by discrete, monodisperse SiO2 nanoparticles (NPs) has been carried out, and the resulting significant enhancement of metal-derived luminescence has been studied to rationalize this dramatic effect. The tetraiminodiphenolate motif chosen for this study is easily synthesized and incorporated into the NP matrix under ambient conditions. The free complex exhibits primarily weak ligand-derived emission at room temperature, typical for these compounds, and displays intense metal-centered luminescence from the europium only when cooled to 77 K. Upon encapsulation by the NPs, however, europium-derived luminescence is visibly "turned on" at room temperature, yielding strong emission peaks characteristic of europium(III) with a corresponding enhancement factor of 6 × 10(6). The similar ligand singlet and triplet excited-state energies determined for the free complex (20820 and 17670 cm(-1), respectively) versus the encapsulated complex (20620 and 17730 cm(-1)) indicate that encapsulation does not affect the energy levels of the ligand appreciably. Instead, a detailed analysis of the metal-centered emission and ligand singlet and triplet emission bands for the free and encapsulated complexes reveals that the enhanced metal emission is due to the rigid environment afforded by the silica NP matrix affecting vibrationally mediated energy transfer. Further, the metal-centered emission lifetimes in methanol versus deuterated methanol indicate a decrease in the number of coordinated solvent molecules upon encapsulation, changing from an average of 3.3 to 2.1 bound methanol molecules and reducing the known quenching effect on europium-centered luminescence due to nearby OH vibrations.

Surveillance of hospital-acquired central line-associated bloodstream infections in pediatric hematology-oncology patients: lessons learned, challenges ahead.

Across 36 US pediatric oncology centers, 576 central line-associated bloodstream infections (CLABSIs) were reported over a 21-month period. Most infections occurred in those with leukemia and/or profound neutropenia. The contribution of viridans streptococci infections was striking. Study findings depict the contemporary epidemiology of CLABSIs in hospitalized pediatric cancer patients.

Effect of a mesitylene-based ligand cap on the relaxometric properties of Gd(III) hydroxypyridonate MRI contrast agents.

A series of new Gd(III) hydroxypyridonate complexes featuring a mesitylene (ME)-derived ligand cap has been prepared. Relaxometric characterization reveals that the complexes tend to form large aggregates in solution with slow tumbling rates, as estimated from NMRD analysis, and unique pH-dependent relaxivities. The solution behavior and relaxometric properties are compared with those observed for analogous TREN-capped compounds, and the potential for use of these new ME-capped complexes as pH-responsive MRI contrast agents is explored.

1,2-hydroxypyridonate/terephthalamide complexes of gadolinium(III): synthesis, stability, relaxivity, and water exchange properties.

Four new Gd(III) complexes based on the 1,2-hydroxypyridinone chelator have been synthesized and evaluated as potential magentic resonance imaging contrast agents. Previously reported work examining Gd-TREN-1,2-HOPO (3; HOPO = hydroxypyridinone) suggests that the 1,2-HOPO unit binds strongly and selectively to Gd(III), encouraging further study of the stability and relaxivity properties of this class of compounds. Among the new complexes presented in this paper are the homopodal Gd-Ser-TREN-1,2-HOPO (Gd-5) and three heteropodal bis-1,2-HOPO-TAM complexes (Gd-6, Gd-7, and Gd-8; TAM = terephthalamide). Conditional stability constants were determined, and all pGd values are in the range of 18.5-19.7, comparable to other analogous HOPO complexes and currently used commercial contrast agents. Relaxivities for all complexes are about twice those of commercial agents, ranging from 7.8 to 10.5 mM(-1) s(-1) (20 MHz; 25 degrees C), and suggest two innersphere water molecules in fast exchange. Luminescent measurements were used to verify the number of coordinated waters for Gd-5, and VT (17)O NMR experiments were employed for the highly soluble Gd-TREN-bis-1,2-HOPO-TAM-N3 (Gd-8) complex to measure a fast water exchange rate, (298)k(ex) = 1/tau(M), of 5.1 (+/-0.4) x 10(8) s(-1) ((298)tau(M) approximately 2 ns).

High-relaxivity MRI contrast agents: where coordination chemistry meets medical imaging.

The desire to improve and expand the scope of clinical magnetic resonance imaging (MRI) has prompted the search for contrast agents of higher efficiency. The development of better agents requires consideration of the fundamental coordination chemistry of the gadolinium(III) ion and the parameters that affect its efficacy as a proton relaxation agent. In optimizing each parameter, other practical issues, such as solubility and in vivo toxicity, must also be addressed, making the attainment of safe, high-relaxivity agents a challenging goal. This Minireview presents recent advances in the field, with an emphasis on gadolinium(III) hydroxypyridinone chelate complexes.

An octadentate luminescent Eu(III) 1,2-HOPO chelate with potent aqueous stability.

The synthesis, characterization, and photophysical properties of two novel ligands, 5LINMe-1,2-HOPO (1) and H(2,2)-1,2-HOPO (2), which utilize the 1,2-HOPO chelate as a sensitizer for Eu(III) are reported. In addition, the former ligand was structurally characterized as the Eu(III) complex by X-ray crystallography. The [Eu(1)2]- complex of the tetradentate ligand (1) is stable in aqueous solution, to a limiting concentration of ca. 7x10(-9) M, and retains the superior photophysical performance noted for the 1,2-HOPO sensitizer. By contrast, the octadentate ligand (2) has vastly improved stability as the [Eu(2)]- complex upon further dilution, to a limiting concentration of ca. 5x10(-17) M, which is beyond the minimum detectable concentration of most fluorimeters. The presence of a single coordinated water molecule for the latter complex reduces the overall metal-centered luminescence.

Highly soluble tris-hydroxypyridonate Gd(III) complexes with increased hydration number, fast water exchange, slow electronic relaxation, and high relaxivity.

The design, synthesis, and relaxivity properties of highly soluble TACN-capped trishydroxypyridonate-Gd(III) complexes are presented. Molecular mechanics modeling was used to help design a complex capable of possessing three water molecules in the inner metal coordination sphere, an attractive property for high-relaxivity MRI contrast agents. The measured relaxivities of 13.1 and 12.5 mM-1 s-1 (20 MHz, 298 K) for two TACN-capped complexes are among the highest known relaxivities of low-molecular weight Gd complexes and are consistent with three coordinated waters, an extremely fast water exchange rate, and long electronic relaxation time. Luminescence measurements to confirm the number of coordinated water molecules for the first time in the HOPO series are also discussed.

"Cymothoe sangaris": an extremely stable and highly luminescent 1,2-hydroxypyridinonate chelate of Eu(III).

The synthesis, structure, and characterization of a new class of luminescent agents based on the 1,2-hydroxypyridinone chelator are reported. The prototype complex, [Eu(5LIO-1,2-HOPO)2]-, demonstrates superb aqueous stability [pEu = 18.64(10)] and is highly emissive [Phit = 0.21(3)], emitting almost pure "red" light (lambdaem = 612 nm). The crystal structure reveals a coordination geometry reminiscent of a "butterfly", hence the soubriquet of "Cymothoe sangaris" to identify with the unique species of red butterfly found only in Central Africa.

Tris(pyrone) chelates of Gd(III) as high solubility MRI-CA.

Two tripodal, hexadentate pyrone-based chelators have been prepared. These ligands form stable, soluble complexes with gadolinium(III). The complexes show aqueous stability comparable to that of [Gd(DTPA)]2- at pH 7.4. Evaluation by relaxometry shows that these complexes have two inner-sphere water molecules and a very fast water exchange rate. The solution behavior of these complexes suggests that they may be attractive as high relaxivity, next-generation magnetic resonance imaging contrast agents.

Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome in children and adolescents.

Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are both uncommon disorders that present with a microangiopathic hemolytic anemia and thrombocytopenia. Although for TTP, neurologic manifestations predominate, and in HUS renal dysfunction is virtually always present, there is significant overlap in their clinical presentation. In recent years, tremendous progress has been made in our understanding of the pathogenesis of these disorders. It is now apparent that there are subcategories of both TTP and HUS that can differ in their clinical manifestations, etiology, and management. For instance, although most cases of HUS are due to infection with organisms that produce Shiga-like toxin, other cases may be caused by defined genetic abnormalities. Similarly, TTP is usually caused by genetic or acquired deficiency of the ADAMTS13 enzyme; however, in other cases the relationship with this enzyme remains to be established. Management includes supportive care, plasma transfusions for genetic protein deficiencies, and plasma exchange transfusion for autoimmune TTP.

Estimating the number of bound waters in Gd(III) complexes revisited. Improved methods for the prediction of q-values.

Two literature computational methods for the prediction of the number of inner-sphere aqua ligands, q, have been applied to a test set of seven Gd(aminocarboxylate) complexes. The first method is based on the hypothesis that q should be proportional to the solvent-accessible surface area of the ligand-complexed Gd ion (Castonguay, L. A., Treasurywala, A. M., Caulfield, T. J., Jaeger, E. P., and Kellar, K. E. (1999) Prediction of q-Values and Conformations of Gadolinium Chelates for Magnetic Resonance Imaging. Bioconjugate Chem. 10, 958). The second method is based on the hypothesis that q-values can be deduced by examining series of steric energy versus ionic radii plots as a function of coordination number (Reichert, D. E., Hancock, R. D., and Welch, M. J. (1996) Molecular Mechanics Investigation of Gadolinium(III) Complexes. Inorg. Chem. 35, 7013). This study identifies deficiencies in these methods and, with respect to the first method, describes some apparent errors. Although neither method was reliable at predicting q, two alternate approaches based on either molecular mechanics strain thresholds or exposed Gd surface area thresholds are shown to predict observed q-values for all Gd aminocarboxylate complexes in the test set.

Parent and physician attitudes regarding electronic communication in pediatric practices.

OBJECTIVE: To determine 1) the electronic mail (e-mail) capabilities of families, general pediatricians (GPs), and subspecialty pediatricians (SPs) from an integrated pediatric health care delivery system and 2) the knowledge base and attitudes of these groups regarding the potential issues involved in using e-mail for physician-patient communication. METHODS: Parents were interviewed in the offices of participating practices using a standardized survey tool. Pediatricians and staff were interviewed using a separate instrument. The data were entered into a database for analysis. RESULTS: A total of 325 parents and 37 physicians were interviewed. Fifty-seven percent of the 161 parents who were interviewed at the GP offices and 66% of the 164 families that were interviewed at SP offices had access to e-mail. Parents aged 31 to 40 years were significantly more likely to have access to e-mail than parents of other age groups. Access to e-mail increased with family income and parental education. Most (74%) parents who were interviewed expressed interest in using e-mail to contact their child's physician/physician's office for several purposes, including getting information or test results, scheduling appointments, and/or discussing a particular symptom. Although both groups of parents expressed concerns about confidentiality, parents at the GP offices were significantly more concerned (median(GP) = 95 vs median(SP) = 70). Seventy-four percent of GPs and 100% of SPs had access to e-mail; however, 79% did not want to use e-mail for physician-patient communication, citing concerns about confidentiality and the time demands that patient e-mail might engender. CONCLUSIONS: The majority of parents and pediatricians at both general and subspecialty pediatric offices are capable of communicating electronically. Parents and pediatricians are aware of the issues surrounding e-mail use for patient communication. Most parents express an interest in using e-mail for patient-physician communications, whereas most physicians are opposed to this practice.

Enhanced selectivity for actinides over lanthanides with CMPO ligands secured to a C(3)-symmetric triphenoxymethane platform.

A ligand system containing three preorganized carbamoylmethylphosphine oxide (CMPO) moieties anchored onto a rigid C(3)-symmetric triphenoxymethane platform has been developed for facile metal complexation and subsequent extraction from aqueous acidic nuclear waste streams. Intended to mimic the 3:1 CMPO-actinide stoichiometry of the extracted species in the TRUEX nuclear waste treatment process, the CMPO arms on this ligand are oriented such that all three CMPO moieties can cooperatively bind a metal ion. Extractions of simulated nuclear waste streams (10(-4) M metal in 1 M nitric acid) with solutions of this ligand in methylene chloride (10(-3) M) reveal a high affinity for the actinide thorium and a very low, but constant, affinity for the lanthanides across the series. Thorium and five lanthanide (lanthanum, cerium, neodymium, europium, and ytterbium) nitrate complexes of this ligand have been synthesized and fully characterized by X-ray crystallography, (1)H and (31)P NMR spectra, and FT-ICR-MS to elucidate the mechanism of this unique actinide selectivity. All six oxygen donors from the three CMPO arms of the ligand and one or two nitrate counterions coordinate these metals to afford 2+ cationic complexes in every case. Because of the large size of the ligand, both the thorium and lanthanide complexes present similarly charged and sized surfaces to the extraction solvents, but the thorium complex is extracted quantitatively over the lanthanide complexes. A possible rationale for this extraction behavior difference is presented and further illustrated by the extraction properties of this ligand system for the alkali metals (lithium, sodium, potassium, rubidium, and cesium) as picrate salts and by the solid- and solution-state structures of its lithium picrate complex.