Lanthanide Identity Governs Guest-Induced Dimerization in LnIII [15-MC Cu II N(L-pheHA) -5])3+ Metallacrowns.

Series of lanthanide-containing metallic coordination complexes are frequently presented as structurally analogous, due to the similar chemical and coordinative properties of the lanthanides. In the case of chiral (LnIII [15-MC Cu II N(L-pheHA) -5])3+ metallacrowns (MCs), which are well established supramolecular hosts, the formation of dimers templated by a dicarboxylate guest (muconate) in solution of neutral pH is herein shown to have a unique dependence on the identity of the MC's central lanthanide. Calorimetric data and nuclear magnetic resonance diffusion studies demonstrate that MCs containing larger or smaller lanthanides as the central metal only form monomeric host-guest complexes whereas analogues with intermediate lanthanides (for example, Eu, Gd, Dy) participate in formation of dimeric host-guest-host compartments. The driving force for the dimerization event across the series is thought to be a competition between formation of highly stable MCs (larger lanthanides) and optimally linked bridging guests (smaller lanthanides).

Iodinated Metallacrowns: Toward Combined Bimodal Near-Infrared and X-Ray Contrast Imaging Agents.

Multimodal probes capable of combining imaging modalities within a single molecule are in high demand today as they can provide information at both molecular and anatomical levels. Herein, a study was conducted on a series of gallium(III)/lanthanide(III) bis(12-MC-4) metallacrowns (MCs) with the general composition {Ln[12-MCGa III N(shi) -4]}2 (iph)4 (Ln-Ix , x=0, 4, 8, 12), where shi and iph are salicylhydroximate and isophthalate ligands, respectively, or their iodinated derivatives. For Yb-Ix , the attenuation in X-ray computed tomography (XCT) imaging and near-infrared (NIR) luminescence properties can be finely tuned by controlled structural modifications based on iodo groups. Solutions of Yb-Ix appear to be 22-40 times more efficient as XCT agents in comparison to the commercially available iobitridol, while providing an intense emission signal in the NIR range with total quantum yields up to 8.6 %, which are among the highest values reported so far. Therefore, these molecules are promising potential bimodal agents for combined NIR luminescence and XCT imaging.

Visible, Near-Infrared, and Dual-Range Luminescence Spanning the 4f Series Sensitized by a Gallium(III)/Lanthanide(III) Metallacrown Structure.

Lanthanide(III) ions (Ln3+) in coordination compounds exhibit unique luminescence properties with narrow and characteristic f-f transitions throughout the visible and near-infrared (NIR) ranges. In addition, some Ln3+ such as Pr3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+ possess an exceptional ability, although less explored, to exhibit dual-range emissions. Such remarkable features allow highly specific use in materials science and biology, for example, for the creation of sophisticated barcode modules or for the next generation of optical imaging applications. Herein, a series of Ga3+/Ln3+ metallacrowns (MCs) with the general composition [LnGa8(shi)8(OH)4]Na·xCH3OH·yH2O (Ln-1, Ln = Pr3+, Nd3+, Sm3+-Yb3+ and analogue Y3+; H3shi = salicylhydroxamic acid) is presented. Ln-1 were obtained by reacting Ga3+ and Ln3+ nitrate salts with the H3shi ligand. X-ray single crystal unit cell analysis confirmed that all MCs are isostructural. The crystal structure was solved for the Nd3+ analogue and revealed that Nd3+ is centered between two [12-MCGaIIIN(shi)-4] MC rings and bound to eight hydroximate oxygen ions (four from each ring) in a pseudosquare antiprismatic fashion adopting a pseudo-D4h symmetry. Pulsed gradient spin echo diffusion ordered 1H NMR spectroscopy and electrospray ionization mass spectrometry confirmed that the structure of Ln-1 remains intact in methanol solutions while mass spectrometry suggests that four OH- bridges are exchanged with CH3O-/CD3O-. An exceptional ability of this series of MCs to sensitize the characteristic emission of Ln3+ was confirmed with the observation of bright red and green emission signals of Eu-1 and Tb-1, NIR emissions of Yb-1 and Nd-1, and dual-range emissions of Pr-1, Sm-1, Dy-1, Ho-1, Er-1, and Tm-1 in the solid state upon excitation into ligand-centered bands at 340 nm. The luminescence properties of Ln-1 (Ln = Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, and Yb3+) were also investigated in CH3OH and CD3OD solutions. For Eu-1 and Yb-1 MCs, more extensive analyses of the photophysical properties were performed, which included the determination of radiative lifetimes, intrinsic quantum yields, and sensitization efficiencies. The absolute quantum yields (QLnL) of Ln-1 in the visible and NIR ranges have been determined. In the case of Sm-1, the values of QLnL in CH3OH and CD3OD solutions are exceptionally high, that is, 10.1(5) and 83(1) %. Values obtained for Yb-1, that is, 0.78(4) % in CH3OH and 8.4(1)% in CD3OD, are among the highest ones reported today for Yb3+ complexes formed with nondeuterated and nonhalogenated ligands.

Reduction of PINK1 or DJ-1 impair mitochondrial motility in neurites and alter ER-mitochondria contacts.

Subcellular distribution of mitochondria in neurons is crucial for meeting the energetic demands, as well as the necessity to buffer Ca2+ within the axon, dendrites and synapses. Mitochondrial impairment is an important feature of Parkinson disease (PD), in which both familial parkinsonism genes DJ-1 and PINK1 have a great impact on mitochondrial function. We used differentiated human dopaminergic neuroblastoma cell lines with stable PINK1 or DJ-1 knockdown to study live motility of mitochondria in neurites. The frequency of anterograde and retrograde mitochondrial motility was decreased in PINK1 knockdown cells and the frequency of total mitochondrial motility events was reduced in both cell lines. However, neither the distribution nor the size of mitochondria in the neurites differed from the control cells even after downregulation of the mitochondrial fission protein, Drp1. Furthermore, mitochondria from PINK1 knockdown cells, in which motility was most impaired, had increased levels of GSK3ßSer9 and higher release of mitochondrial Ca2+ when exposed to CCCP-induced mitochondrial uncoupling. Further analysis of the ER-mitochondria contacts involved in Ca2+ shuttling showed that PINK1 knockdown cells had reduced contacts between the two organelles. Our results give new insight on how PINK1 and DJ-1 influence mitochondria, thus providing clues to novel PD therapies.

[18F]FSPG-PET reveals increased cystine/glutamate antiporter (xc-) activity in a mouse model of multiple sclerosis.

BACKGROUND: The cystine/glutamate antiporter (xc-) has been implicated in several neurological disorders and, specifically, in multiple sclerosis (MS) as a mediator of glutamate excitotoxicity and proinflammatory immune responses. We aimed to evaluate an xc-specific positron emission tomography (PET) radiotracer, (4S)-4-(3-[18F]fluoropropyl)-L-glutamate ([18F]FSPG), for its ability to allow non-invasive monitoring of xc- activity in a mouse model of MS. METHODS: Experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice by subcutaneous injection of myelin oligodendrocyte glycoprotein (MOG35-55) peptide in complete Freund's adjuvant (CFA) followed by pertussis toxin. Control mice received CFA emulsion and pertussis toxin without MOG peptide, while a separate cohort of naïve mice received no treatment. PET studies were performed to investigate the kinetics and distribution of [18F]FSPG in naïve, control, pre-symptomatic, and symptomatic EAE mice, compared to 18F-fluorodeoxyglucose ([18F]FDG). After final PET scans, each mouse was perfused and radioactivity in dissected tissues was measured using a gamma counter. Central nervous system (CNS) tissues were further analyzed using ex vivo autoradiography or western blot. [18F]FSPG uptake in human monocytes, and T cells pre- and post-activation was investigated in vitro. RESULTS: [18F]FSPG was found to be more sensitive than [18F]FDG at detecting pathological changes in the spinal cord and brain of EAE mice. Even before clinical signs of disease, a small but significant increase in [18F]FSPG signal was observed in the spinal cord of EAE mice compared to controls. This increase in PET signal became more pronounced in symptomatic EAE mice and was confirmed by ex vivo biodistribution and autoradiography. Likewise, in the brain of symptomatic EAE mice, [18F]FSPG uptake was significantly higher than controls, with the largest changes observed in the cerebellum. Western blot analyses of CNS tissues revealed a significant correlation between light chain of xc- (xCT) protein levels, the subunit of xc- credited with its transporter activity, and [18F]FSPG-PET signal. In vitro [18F]FSPG uptake studies suggest that both activated monocytes and T cells contribute to the observed in vivo PET signal. CONCLUSION: These data highlight the promise of [18F]FSPG-PET as a technique to provide insights into neuroimmune interactions in MS and the in vivo role of xc- in the development and progression of this disease, thus warranting further investigation.

Chemically Stable Styrenic Electrospun Membranes with Tailorable Surface Chemistry.

Membranes with tailorable surface chemistry have applications in a wide range of industries. Synthesizing membranes from poly(chloromethyl styrene) directly incorporates an alkyl halide surface-bound initiator which can be used to install functional groups via SN2 chemistry or graft polymerization techniques. In this work, poly(chloromethyl styrene) membranes were synthesized through electrospinning. After fabrication, membranes were crosslinked with a diamine, and the chemical resistance of the membranes was evaluated by exposure to 10 M nitric acid, ethanol, or tetrahydrofuran for 24 h. The resulting membranes had diameters on the order of 2-5 microns, porosities of >80%, and permeance on the order of 10,000 L/m2/h/bar. Crosslinking the membranes generally increased the chemical stability. The degree of crosslinking was approximated using elemental analysis for nitrogen and ranged from 0.5 to 0.9 N%. The poly(chloromethyl styrene) membrane with the highest degree of crosslinking did not dissolve in THF after 24 h and retained its high permeance after solvent exposure. The presented chemically resistant membranes can serve as a platform technology due to their versatile surface chemistry and can be used in membrane manufacturing techniques that require the membrane to be contacted with organic solvents or monomers. They can also serve as a platform for separations that are performed in strong acids.

Spectrum of 68Ga-DOTA TATE Uptake in Patients With Neuroendocrine Tumors.

PURPOSE: To analyze the biodistribution of Ga-DOTA-TATE in the normal tissues and uptake in benign, indeterminate, and malignant lesions in a population of patients with known neuroendocrine tumors (NET) using semiquantitative standardized uptake values (SUV) measurements. METHODS: One hundred four consecutively scanned patients (51 men and 53 women; mean age, 56.4 years) with confirmed diagnosis of NET underwent PET/CT 1 hour after administration of Ga-DOTA-TATE. SUVmean, and SUVmax were measured in 37 normal anatomical structures for each patient. Abnormal uptake was divided into benign, indeterminate, and malignant categories based on imaging characteristic, clinical follow-up, and pathology. RESULTS: High physiologic uptake (SUVmax > 7) was observed in spleen, renal parenchyma, adrenal glands, pituitary gland, stomach, and liver (in decreasing order). Moderate uptake (3.5-7) was present in the prostate, jejunum, pancreas, ileum, and salivary glands. Mild uptake (2-3.5) was present in the uterus, colon, thyroid, rectum, and skeleton. A total of 678 lesions (limited to 5 lesions with highest uptake per organ) were included in the analysis, including 127 benign and 54 indeterminate lesions. Uptake was significantly higher in malignant lesions than in benign lesions, but an overlap was noted between the groups. CONCLUSIONS: Ga-DOTA TATE uptake in normal and abnormal structures is highly variable in patients with NET. SUV is a useful measure for characterizing benign versus malignant lesions. Anatomical and clinical correlation may be necessary to characterize foci of intermediate uptake.

Pilot Comparison of 68Ga-RM2 PET and 68Ga-PSMA-11 PET in Patients with Biochemically Recurrent Prostate Cancer.

UNLABELLED: Glu-NH-CO-NH-Lys-(Ahx)-[(68)Ga(HBED-CC)] ((68)Ga-PSMA-11) is a PET tracer that can detect prostate cancer relapses and metastases by binding to the extracellular domain of PSMA. (68)Ga-labeled DOTA-4-amino-1-carboxymethyl-piperidine-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 ((68)Ga-RM2) is a synthetic bombesin receptor antagonist that targets gastrin-releasing peptide receptors. We present pilot data on the biodistribution of these PET tracers in a small cohort of patients with biochemically recurrent prostate cancer. METHODS: Seven men (mean age ± SD, 74.3 ± 5.9 y) with biochemically recurrent prostate cancer underwent both (68)Ga-PSMA-11 PET/CT and (68)Ga-RM2 PET/MRI scans. SUVmax and SUVmean were recorded for normal tissues and areas of uptake outside the expected physiologic biodistribution. RESULTS: All patients had a rising level of prostate-specific antigen (mean ± SD, 13.5 ± 11.5) and noncontributory results on conventional imaging. (68)Ga-PSMA-11 had the highest physiologic uptake in the salivary glands and small bowel, with hepatobiliary and renal clearance noted, whereas (68)Ga-RM2 had the highest physiologic uptake in the pancreas, with renal clearance noted. Uptake outside the expected physiologic biodistribution did not significantly differ between (68)Ga-PSMA-11 and (68)Ga-RM2; however, (68)Ga-PSMA-11 localized in a lymph node and seminal vesicle in a patient with no abnormal (68)Ga-RM2 uptake. Abdominal periaortic lymph nodes were more easily visualized by(68)Ga-RM2 in two patients because of lack of interference by radioactivity in the small intestine. CONCLUSION: (68)Ga-PSMA-11 and (68)Ga-RM2 had distinct biodistributions in this small cohort of patients with biochemically recurrent prostate cancer. Additional work is needed to understand the expression of PSMA and gastrin-releasing peptide receptors in different types of prostate cancer.