Synthesis, structures and cytotoxicity studies of p-sulfonatocalix[4]arene lanthanide complexes

A number of p-sulfonatocalix[4]arene complexes of the lanthanides (Tb, Gd, and Eu) have been prepared, some in the presence of tetraazamacrocycle 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A), and fully characterised. Crystal structure determinations reveal lanthanide coordination at the sulfonate group, bridging several calixarene units, giving coordination polymers. All complexes in this study have been determined to be relatively non-toxic using in vitro cell assays with CC₅₀ values in the range 30–170 μM

Synthesis, structure, and cytotoxicity studies of oxidovanadium(IV and V) complexes bearing chelating phenolates

The interaction of [VO(acac)2] with 2,6-bis(hydroxymethyl)-4-methylphenol (L1H3) or 6,6/-methylenebis(4-tert-butyl-2-(hydroxymethyl)phenol) (L2H4) in refluxing toluene afforded, following work-up in ethanol, the complexes [VOL1]2 (1) and {[VO(acac)(HOEt)](VO)L2]}2 (2), respectively. Use of 4-[3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl]benzoic acid (L3H2) or 4-[3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl]benzosulfonic acid (L4H2) with [VOCl3] in refluxing acetonitrile, followed by methanol and THF work-up, afforded the complexes [Et3NH][VO(OMe)L3]2 (3) and [Et3NH][VO(OMe)L4]2 (4), respectively. The interaction of [VOSO4] and L3H2 in refluxing acetonitrile afforded, with extraction into methanol, the complex [VO(OMe)L3]2 (5). The molecular structures of 2, 3 and 5 have been determined; the structure of 1 has been reported previously. The complexes in this study have been determined to be of low toxicity using in vitro cell assays with 50% cytotoxicity values (CC50) values in the range 56 – 126 µM

Chelator free gallium-68 radiolabelling of silica coated iron oxide nanorods via surface interactions

The commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron–oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T₂ MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging

Structurally optimised BODIPY derivatives for imaging of mitochondrial dysfunction in cancer and heart cells

The structural features required for mitochondrial uptake of BODIPY-based optical imaging agents have been explored. The first derivatives of this class of dyes shown to have mitochondrial membrane potential-dependent uptake in both cancer and heart cells have been developed

64Cu PET Imaging of the CXCR4 Chemokine Receptor Using a Cross-Bridged Cyclam Bis-Tetraazamacrocyclic Antagonist

© 2020 by the Society of Nuclear Medicine and Molecular Imaging. Expression of the chemokine receptor chemokine C-X-C motif receptor 4 (CXCR4) plays an important role in cancer metastasis, in autoimmune diseases, and during stem cell-based repair processes after stroke and myocardial infarction. Previously reported PET imaging agents targeting CXCR4 suffer from either high nonspecific uptake or bind only to the human form of the receptor. The objective of this study was to develop a high-stability 64Cu-labeled small-molecule PET agent for imaging both human and murine CXCR4 chemokine receptors. Methods: Synthesis, radiochemistry, stability and radioligand binding assays were performed for the novel tracer 64Cu-CuCB-bicyclam. In vivo dynamic PET studies were performed on mice bearing U87 (CXCR4 low-expressing) and U87.CXCR4 (human-CXCR4 high-expressing) tumors. Biodistribution and receptor blocking studies were performed on CD1-IGS immunocompetent mice. CXCR4 expression on tumor and liver disaggregates was confirmed using a combination of immunohistochemistry, quantitative polymerase chain reaction, and Western blot. Results:64Cu-CuCB-bicyclam has a high affinity for both the human and the murine variants of the CXCR4 receptor (half-maximal inhibitory concentration, 8 nM [human]/2 nM [murine]) and can be obtained from the parent chelator that has low affinity. In vitro and in vivo studies demonstrate specific uptake in CXCR4-expressing cells that can be blocked by more than 90% using a higher-affinity antagonist, with limited uptake in non-CXCR4-expressing organs and high in vivo stability. The tracer was also able to selectively displace the CXCR4 antagonists AMD3100 and AMD3465 from the liver. Conclusion: The tetraazamacrocyclic small molecule 64Cu-CuCB-bicyclam has been shown to be an imaging agent for the CXCR4 receptor that is likely to be applicable across a range of species. It has high affinity and stability and is suitable for preclinical research in immunocompetent murine models

Validation of methods for measuring the efficiency of inorganic nucleases

Dissertação de Mestrado, Qualidade em Análises, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2011O estudo e desenvolvimento de metalonucleases com a capacidade de clivar específica e selectivamente o DNA é um desafio fascinante. Estas, também denominadas como nucleases artificiais, são desenhadas com o objectivo principal de competir com os enzimas. Os metais de transição têm despertado um elevado interesse nesta área uma vez que possuem propriedades específicas que lhes conferem a capacidade de interagir especificamente com o DNA

o-BF3-Phosphonium pincer moieties in the design of delocalized lipophilic cation based tracers for PET imaging of mitochondrial function

International audienceObjectives: Delocalized lipophilic cations, such as triphenylphosphonium (TPP), are able to cross cell membranes and are known to accumulate in the mitochondria in a membrane potential (MMP) dependent manner. MMP is a reliable indicator of mitochondrial and, consequently, cell and tissue function, hence MMP dependent uptake radiotracers are of interest in cardiac and tumour imaging. Conventional C-18F radiofluorination methods require strict aprotic conditions and heating, moreover, C-18F fluorinated tracers may suffer from metabolic defluorination reducing the quality of the images. The objective of this study was to investigate a suitability of o-B[18F]F3-phosphonium pincer moiety, easily accessible via radiofluorination of boronic ester precursors in aqueous mixtures to give high stability, for use as MMP dependent tracers.Methods: Required boronic ester precursors and cold 19F-fluorine labelled reference compounds 1-4 (Fig. 1) were prepared and purified following modified published synthetic protocols. Radiofluorination was carried out in a 0.2 mg scale with carrier added 18F-fluoride at 55oC in 30 min in 20% acetonitrile / water mixture acidified by addition of concentrated hydrochloric acid. LogD7.4 values were determined via the shake flask method. Stability in human serum was assessed using radio-HPLC analysis. The isolated mitochondria uptake assay was performed on freshly isolated mitochondria from Sprague-Dawley rat heart tissue. Cell uptake of the tracer was measured in normal H9c2 cardiac and U87 tumour cells in presence and absence of a membrane depolarizing agent 2-[2-(3-chlorophenyl)hydrazineylyidene]propanedinitrile (CCCP). PET/CT imaging and biodistribution studies were performed in CD-1 nude mice bearing U87 tumour xenografts. Overall charge distributions were calculated using fully optimised geometries at TPSS-D3/def2-TZVPP theory level. 18FHTP (6-18F-fluorohexyltriphenylphosphonium) was prepared in an original one step radiolabelling procedure from an iodinated precursor and was used to validate all assays and as a benchmark for the novel tracers.Results: 18FHTP and 18F-1-4 were obtained in 20-25% decay corrected radiochemical yields within 60 min from the end of bombardment. The LogD7.4 values ranged between 1.78±0.06 (18FHTP and 18F-2) and 0.52±0.01 (18F-1), with 0.88±0.09 and 1.11±0.08 for 18F-3 and 18F-4, respectively. All radiotracers showed 蠅 95% stability in human serum for 3 h. Tracers 18FHTP and 18F-2 showed a comparable MMP dependent uptake in isolated mitochondria (~8%), with the uptake of 18F-3 and 18F-4 below 4% and MMP independent, indicating the importance of the lipophilicity. U87 cell uptake of all tracers was low and MMP independent (~ 0.1% and 1% for 18FHTP and 18F-1-4 respectively). 18F-2 showed the highest and the only MMP dependent cell uptake from the series of new compounds(~ 4% vs ~7% observed for 18FHTP). None of BF3 group containing tracers showed any cardiac or tumour uptake in vivo. Overall charge distribution analysis in a computational study revealed a localised positive charge at the boron atom with partial negative charges carried by fluorine atoms or an ipso carbon of one of the unsubstituted phenyl rings.Conclusion: A series of o-BF3 substituted triphenylphosphonium tracers were successfully synthesized and radiolabelled with fluorine-18. A preliminary in vitro investigation confirmed the importance of the lipophilicity for mitochondrial uptake of the tracer, however, this was not sufficient to ensure cell membrane transport and consequent in vivo localization. The comparison of overall charge distribution maps suggests that addition of a BF3 group introduces a localized charge which is not compensated for by the charge of phosphonium and cannot be delocalised into the phenyl rings

Multivalency in CXCR4 chemokine receptor targeted iron oxide nanoparticles

The CXCR4 chemokine receptor is an important biomolecular target in cancer diagnostics and therapeutics. In a new multivalent approach, iron oxide nanoparticles were conjugated with multiple binding units of a low affinity azamacrocylic CXCR4 antagonist. The silica coated nanostructure has good suspension stability, a mode size of 72 nm and high affinity for CXCR4, showing >98% inhibition of anti-CXCR4 mAb binding in a receptor binding competition assay on Jurkat cells

Towards dual SPECT/optical bioimaging with a mitochondrial targeting, Tc-99m(i) radiolabelled 1,8-naphthalimide conjugate

A series of six different 1,8-naphthalimide conjugated dipicolylamine ligands (L1-6) have been synthesised and characterised. The ligands possess a range of different linker units between the napthalimide fluorophore and dipcolylamine chelator which allow the overall lipophilicity to be tuned. A corresponding series of Re(i) complexes have been synthesised of the form fac-[Re(CO)3(L1-6)]BF4. The absorption and luminescence properties of the ligands and Re(i) complexes were dominated by the intramolecular charge transfer character of the substituted fluorophore (typically absorption ca. 425 nm and emission ca. 520 nm). Photophysical assessments show that some of the variants are moderately bright. Radiolabelling experiments using a water soluble ligand variant (L5) were successfully undertaken and optimised with fac-[99mTc(CO)3(H2O)3]+. Confocal fluorescence microscopy showed that fac-[Re(CO)3(L5)]+ localises in the mitochondria of MCF-7 cells. SPECT/CT imaging experiments on naïve mice showed that fac-[99mTc(CO)3(L5)]+ has a relatively high stability in vivo but did not show any cardiac uptake, demonstrating rapid clearance, predominantly via the biliary system along with a moderate amount cleared renally.status: publishe

Chelator free gallium-68 radiolabelling of silica coated iron oxide nanorods via surface interactions

International audienceThe commercial availability of combined magnetic resonance imaging (MRI)/positron emission tomography (PET) scanners for clinical use has increased demand for easily prepared agents which offer signal or contrast in both modalities. Herein we describe a new class of silica coated iron–oxide nanorods (NRs) coated with polyethylene glycol (PEG) and/or a tetraazamacrocyclic chelator (DO3A). Studies of the coated NRs validate their composition and confirm their properties as in vivo T2 MRI contrast agents. Radiolabelling studies with the positron emitting radioisotope gallium-68 (t1/2 = 68 min) demonstrate that, in the presence of the silica coating, the macrocyclic chelator was not required for preparation of highly stable radiometal-NR constructs. In vivo PET-CT and MR imaging studies show the expected high liver uptake of gallium-68 radiolabelled nanorods with no significant release of gallium-68 metal ions, validating our innovation to provide a novel simple method for labelling of iron oxide NRs with a radiometal in the absence of a chelating unit that can be used for high sensitivity liver imaging