Publications by authors named "Bernhard K Keppler"

333 Publications

Modified amino-dextrans as carriers of Gd-chelates for retrograde transport and visualization of peripheral nerves by magnetic resonance imaging (MRI).

J Inorg Biochem 2021 May 29;222:111495. Epub 2021 May 29.

Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Structural Preclinical Imaging, Medical University of Vienna & General Hospital of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria.

Amino-dextrans (AD) conjugated with gadolinium (Gd) were developed as neuro-specific contrast agents (CA) for the visualization of the sciatic nerve in rats by magnetic resonance imaging (MRI). AD with 3, 10, and 70 kDa molecular weights were assessed as carrier molecules known to be transported with various speed by axonal microtubules. Detailed spectroscopic characterizations, analyses by Fast Protein Liquid Chromatography (FPLC), Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), and inductively coupled plasma-mass spectrometry (ICP-MS), were carried out. For MRI, the paramagnetic Gd ion was coupled as a T1 signal enhancer. The well-established linear chelator, diethylenetriaminepentaacetic acid (DTPA), was used and subsequently replaced by the more stable cyclic chelator 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). In addition, a fluorescently labeled AD-DTPA-Gd was prepared to demonstrate an active transport to the spinal cord by histochemistry. After successful synthesis and characterization, molecular migration of the AD-DTPA-Gd in the sciatic nerve of healthy Sprague Dawley rats was monitored by MRI for up to seven days. Enhancement of nerve structures was evaluated by MRI and correlated with ICP-MS analyses. To investigate the distribution of CA along the neuraxis, all animals were sacrificed after the final MRI monitoring. Nerves, spinal ganglions, and corresponding spinal cord sections were harvested, to determine the localization and concentration of the paramagnetic element. This is the first report that demonstrates the active uptake and transport of AD-Gd conjugates within the sciatic nerve. This new concept may serve as a potential diagnostic tool for the direct visualization and monitoring of the continuity of injured nerves.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jinorgbio.2021.111495DOI Listing
May 2021

Effects of N-terminus modified Hx-amides on DNA binding affinity, sequence specificity, cellular uptake, and gene expression.

Bioorg Med Chem Lett 2021 May 28:128158. Epub 2021 May 28.

Cancer Research UK Drug-DNA Interactions Research Group, UCL Cancer Institute, London WC1E 6BT, United Kingdom.

Five X-HxIP (Hx-amides) 6a-e, in which the N-terminus p-anisyl moiety is modified, were designed and synthesised with the purpose of optimising DNA binding, improving cellular uptake/nuclear penetration, and enhancing the modulation of the topoisomerase IIα (TOP2A) gene expression. The modifications include a fluorophenyl group and other heterocycles bearing different molecular shapes, size, and polarity. Like their parent compound HxIP 3, all five X-HxIP analogues bind preferentially to their cognate sequence 5'-TACGAT-3', which is found embedded on the 5' flank of the inverted CCAAT box-2 (ICB2) site in the TOP2A gene promoter, and inhibit protein complex binding, as evidenced in a cell free system. Interestingly, the 4-pyridyl analog 6a exhibits greater binding affinity for the target DNA sequence and abolishes the protein:ICB2 interaction in vitro, at a lower concentration, compared to the prototypical compound HxIP 3. Analogues 6b-e, display improved DNA sequence specificity, but reduced binding affinity for the cognate sequence, relative to the unmodified HxIP 3, with polyamides 6b and 6e being the most sequence selective. However, unlike 3 and 6b, 6a was unable to enter cells, access the nucleus and thereby affect TOP2A gene expression in confluent human lung cancer cells. These results show that while DNA binding affinity and sequence selectivity are important, consideration of cellular uptake and concentration in the nucleus are critical when exerting biological activity is the desired outcome. By characterising the DNA binding, cellular uptake and gene regulatory properties of these small molecules, we can elucidate the determinants of the elicited biological activity, which can be impacted by even small structural modifications in the polyamide molecular design.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bmcl.2021.128158DOI Listing
May 2021

Development of a cobalt(iii)-based ponatinib prodrug system.

Inorg Chem Front 2021 Mar 30;8(10):2468-2485. Epub 2021 Mar 30.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna Waehringer Straße 42 1090 Vienna Austria.

Receptor tyrosine kinase inhibitors have become a central part of modern targeted cancer therapy. However, their curative potential is distinctly limited by both rapid resistance development and severe adverse effects. Consequently, tumor-specific drug activation based on prodrug designs, exploiting tumor-specific properties such as hypoxic oxygen conditions, is a feasible strategy to widen the therapeutic window. After proof-of-principal molecular docking studies, we have synthesized two cobalt(iii) complexes using a derivative of the clinically approved Abelson (ABL) kinase and fibroblast growth factor receptor (FGFR) inhibitor ponatinib. Acetylacetone (acac) or methylacetylacetone (Meacac) have been used as ancillary ligands to modulate the reduction potential. The ponatinib derivative, characterized by an ethylenediamine moiety instead of the piperazine ring, exhibited comparable cell-free target kinase inhibition potency. Hypoxia-dependent release of the ligand from the cobalt(iii) complexes was proven by changed fluorescence properties, enhanced downstream signaling inhibition and increased anticancer activity in BCR-ABL- and FGFR-driven cancer models. Respective tumor-inhibiting effects in the BCR-ABL-driven K-562 leukemia model were restricted to the cobalt(iii) complex with the higher reduction potential and confirmed in a FGFR-driven urothelial carcinoma xenograft model. Summarizing, we here present for the first time hypoxia-activatable prodrugs of the clinically approved tyrosine kinase inhibitor ponatinib and a correlation of the activity with their reduction potential.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d1qi00211bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8129988PMC
March 2021

Multifunctional Pt(IV) prodrug candidates featuring the carboplatin core and deferoxamine.

Dalton Trans 2021 May 25. Epub 2021 May 25.

Institute of Inorganic Chemistry, University of Vienna, Waehringer Str. 42, 1090 Vienna, Austria. and Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1/III, 8010 Graz, Austria.

The synergistic combination of the anticancer drug carboplatin and the iron chelator deferoxamine (DFO) served as a foundation for the development of novel multifunctional prodrugs. Hence, five platinum(iv) complexes, featuring the equatorial coordination sphere of carboplatin, and one or two DFO units incorporated at axial positions, were synthesized and characterized using ESI-HRMS, multinuclear (1H, 13C, 15N, 195Pt) NMR spectroscopy and elemental analysis. Analytical studies demonstrated that the chelating properties of the DFO moiety were not compromised after coupling to the platinum(iv) core. The cytotoxic activity of the compounds was evaluated in monolayer (2D) and spheroid (3D) cancer cell models, derived from ovarian teratocarcinoma (CH1/PA-1), colon carcinoma (SW480) and non-small cell lung cancer (A549). The platinum(iv)-DFO prodrugs demonstrated moderate in vitro cytotoxicity (a consequence of their slow activation kinetics) but with less pronounced differences between intrinsically chemoresistant and chemosensitive cell lines as well as between 2D and 3D models than the clinically used platinum(ii) drug carboplatin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d1dt00214gDOI Listing
May 2021

Micro-droplet-based calibration for quantitative elemental bioimaging by LA-ICPMS.

Anal Bioanal Chem 2021 May 5. Epub 2021 May 5.

Institute of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 38, 1090, Vienna, Austria.

In this work, a novel standardization strategy for quantitative elemental bioimaging is evaluated. More specifically, multi-element quantification by laser ablation-inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-TOFMS) is performed by multi-point calibration using gelatin-based micro-droplet standards and validated using in-house produced reference materials. Fully automated deposition of micro-droplets by micro-spotting ensured precise standard volumes of 400 ± 5 pL resulting in droplet sizes of around 200 μm in diameter. The small dimensions of the micro-droplet standards and the use of a low-dispersion laser ablation setup reduced the analysis time required for calibration by LA-ICPMS significantly. Therefore, as a key advance, high-throughput analysis (pixel acquisition rates of more than 200 Hz) enabled to establish imaging measurement sequences with quality control- and standardization samples comparable to solution-based quantification exercises by ICP-MS. Analytical figures of merit such as limit of detection, precision, and accuracy of the calibration approach were assessed for platinum and for elements with biological key functions from the lower mass range (phosphorus, copper, and zinc). As a proof-of-concept application, the tool-set was employed to investigate the accumulation of metal-based anticancer drugs in multicellular tumor spheroid models at clinically relevant concentrations. Graphical abstract.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00216-021-03357-wDOI Listing
May 2021

Complex formation of an estrone-salicylaldehyde semicarbazone hybrid with copper(II) and gallium(III): Solution equilibria and biological activity.

J Inorg Biochem 2021 Jul 24;220:111468. Epub 2021 Apr 24.

Department of Inorganic and Analytical Chemistry, Interdisciplinary Excellence Centre, University of Szeged, Dóm tér 7, H-6720 Szeged, Hungary; MTA-SZTE Lendület Functional Metal Complexes Research Group, University of Szeged, Dóm tér 7, H-6720 Szeged, Hungary.

The solution chemical properties such as proton dissociation, complex formation with copper(II) and gallium(III) ions in addition to antibacterial and antitumor activity of a novel tridentate salicyaldehyde semicarbazone-estrone hybrid (estrone-SC) and a related bicyclic compound (thn-SC) were investigated. The crystal structure of complex [Cu(thn-SCH)Cl] was studied by single crystal X-ray diffraction method. Estrone-SC and thn-SC form mono-ligand complexes with Cu(II) characterized by relatively high stability, however, they are much less stable than their thiosemicarbazone analogues. The neutral Cu(II) complexes with (O,N,O)(HO) coordination mode predominate at physiological pH. Estrone-SC and thn-SC are more efficient Ga(III) binders in comparison with thiosemicarbazones, although the complexes also suffer dissociation at pH 7.4. The Cu(II) complex of estrone-SC displayed significant cytotoxicity in A549, SW480 and CH1/PA cancer cells, and moderate apoptosis induction and ROS formation. The semicarbazone compounds did not exhibit antibacterial effect; unlike the related Cu(II)-thiosemicarbazone complexes represented by the fairly low MIC values (3-50 μM) obtained on the Gram-positive Staphylococcus aureus and Enterococcus faecalis bacteria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jinorgbio.2021.111468DOI Listing
July 2021

Toward a deeper and simpler understanding of serum protein-mediated transformations of magnetic nanoparticles by ICP-MS.

Talanta 2021 Jul 11;229:122287. Epub 2021 Mar 11.

Vernadsky Institute of Geochemistry and Analytical Chemistry, 119991, Moscow, Russian Federation. Electronic address:

A great variety of magnetic nanomaterials are entering preclinical investigations with the objective to select the most promising candidates for diagnostic and therapeutic applications. For an analytical approach to be used as a high-throughput screening tool, simple and cost-efficient sample preparation protocol is a basiс prerequisite. Here, we demonstrate how the application of continuous magnetic field allows for quantitatively separating iron oxide magnetic nanoparticles from a mixture with human serum to facilitate monitoring of their biomolecular interactions with high-resolution inductively coupled plasma mass spectrometry. By measuring the signals of sulfur and metal isotopes, it is possible to monitor the formation of the protein corona and alterations in the concentrations of relevant metals due to binding of specific metalloproteins, respectively.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.talanta.2021.122287DOI Listing
July 2021

Current trends and challenges in analysis and characterization of engineered nanoparticles in seawater.

Talanta 2021 May 6;226:122201. Epub 2021 Feb 6.

Institute of Inorganic Chemistry, University of Vienna, 1090, Vienna, Austria.

With the increasingly wide use of engineered nanoparticles (ENPs), their release into the environment makes it important to determine in what quantitates they occur in aquatic systems and to understand their fate therein. In particular, detection and quantification of ENPs in seawater is challenging and often requires analytical methods to perform close to the feasibility confines. This review is aimed at critical analysis of current and emerging capabilities of analytical methods as have been employed for the analysis and characterization of ENPs in seawater in the last decade. An emphasis is given to the most reliable experimental strategies focused on avoiding the high-salt matrix effect and isolation and enrichment of the nanoparticulate fraction prior to analysis. Advanced analytical methodology in use basically relies on the application of elemental mass spectrometry to determine various particle-core metals and its single-particle mode to characterize the seawater-mediated transformation of ENPs, including dissolution, aggregation, etc. On the other hand, common microscopy, light scattering or X-ray based techniques are not sensitive enough to acquire the transformation information from real seawater samples. Finally, attention is pinpointed upon an acute shortcoming of the current research which is in the overwhelming majority of cases restricted to samples spiked with ENPs and often at excessive concentration levels.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.talanta.2021.122201DOI Listing
May 2021

Mass spectrometry techniques for imaging and detection of metallodrugs.

Curr Opin Chem Biol 2021 04 31;61:123-134. Epub 2021 Jan 31.

Institute of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 38, 1090, Vienna, Austria. Electronic address:

Undoubtedly, metallomic approaches based on mass spectrometry have evolved into essential tools supporting the drug development of novel metal-based anticancer drugs. This article will comment on the state-of-the-art instrumentation and highlight some of the recent analytical advances beyond routine, especially focusing on the latest developments in inductively coupled plasma-mass spectrometry (ICP-MS). Mass spectrometry-based bioimaging and single-cell methods will be presented, paving the way to exciting investigations of metal-based anticancer drugs in heterogeneous and structurally, as well as functionally complex solid tumor tissues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cbpa.2020.12.005DOI Listing
April 2021

Interaction with Ribosomal Proteins Accompanies Stress Induction of the Anticancer Metallodrug BOLD-100/KP1339 in the Endoplasmic Reticulum.

Angew Chem Int Ed Engl 2021 03 1;60(10):5063-5068. Epub 2021 Feb 1.

Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Str. 38, 1090, Vienna, Austria.

The ruthenium-based anticancer agent BOLD-100/KP1339 has shown promising results in several in vitro and in vivo tumour models as well as in early clinical trials. However, its mode of action remains to be fully elucidated. Recent evidence identified stress induction in the endoplasmic reticulum (ER) and concomitant down-modulation of HSPA5 (GRP78) as key drug effects. By exploiting the naturally formed adduct between BOLD-100 and human serum albumin as an immobilization strategy, we were able to perform target-profiling experiments that revealed the ribosomal proteins RPL10, RPL24, and the transcription factor GTF2I as potential interactors of this ruthenium(III) anticancer agent. Integrating these findings with proteomic profiling and transcriptomic experiments supported ribosomal disturbance and concomitant induction of ER stress. The formation of polyribosomes and ER swelling of treated cancer cells revealed by TEM validated this finding. Thus, the direct interaction of BOLD-100 with ribosomal proteins seems to accompany ER stress-induction and modulation of GRP78 in cancer cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202015962DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7986094PMC
March 2021

Plecstatin-1 induces an immunogenic cell death signature in colorectal tumour spheroids.

Metallomics 2020 12;12(12):2121-2133

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 42, 1090, Vienna, Austria.

Organometallic metal(arene) anticancer agents were believed to confer low selectivity for potential cellular targets. However, the ruthenium(arene) pyridinecarbothioamide (plecstatin-1) showed target selectivity for plectin, a scaffold protein and cytolinker. We employed a three-dimensional cancer spheroid model and showed that plecstatin-1 limited spheroid growth, induced changes in the morphology and in the architecture of tumour spheroids by disrupting the cytoskeletal organization. Additionally, we demonstrated that plecstatin-1 induced oxidative stress, followed by the induction of an immunogenic cell death signature through phosphorylation of eIF2α, exposure of calreticulin, HSP90 and HSP70 on the cell membrane and secretion of ATP followed by release of high mobility group box-1.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0mt00227eDOI Listing
December 2020

Improving the Stability of EGFR Inhibitor Cobalt(III) Prodrugs.

Inorg Chem 2020 Dec 21;59(23):17794-17810. Epub 2020 Nov 21.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Straße 42, 1090 Vienna, Austria.

Although tyrosine kinase inhibitors (TKIs) have revolutionized cancer therapy in the past two decades, severe drawbacks such as strong adverse effects and drug resistance limit their clinical application. Prodrugs represent a valuable approach to overcoming these disadvantages by administration of an inactive drug with tumor-specific activation. We have recently shown that hypoxic prodrug activation is a promising strategy for a cobalt(III) complex bearing a TKI of the epidermal growth factor receptor (EGFR). The aim of this study was the optimization of the physicochemical properties and enhancement of the stability of this compound class. Therefore, we synthesized a series of novel derivatives to investigate the influence of the electron-donating properties of methyl substituents at the metal-chelating moiety of the EGFR inhibitor and/or the ancillary acetylacetonate (acac) ligand. To understand the effect of the different methylations on the redox properties, the newly synthesized complexes were analyzed by cyclic voltammetry and their behavior was studied in the presence of natural low-molecular weight reducing agents. Furthermore, it was proven that reduction to cobalt(II) resulted in a lower stability of the complexes and subsequent release of the coordinated TKI ligand. Moreover, the stability of the cobalt(III) prodrugs was investigated in blood serum as well as in cell culture by diverse cell and molecular biological methods. These analyses revealed that the complexes bearing the methylated acac ligand are characterized by distinctly enhanced stability. Finally, the cytotoxic activity of all new compounds was tested in cell culture under normoxic and various hypoxic conditions, and their prodrug nature could be correlated convincingly with the stability data. In summary, the performed chemical modifications resulted in new cobalt(III) prodrugs with strongly improved stabilities together with retained hypoxia-activatable properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.0c03083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7724630PMC
December 2020

Cancer Cell Resistance Against the Clinically Investigated Thiosemicarbazone COTI-2 Is Based on Formation of Intracellular Copper Complex Glutathione Adducts and ABCC1-Mediated Efflux.

J Med Chem 2020 11 15;63(22):13719-13732. Epub 2020 Nov 15.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, Vienna 1090, Austria.

COTI-2 is a novel anticancer thiosemicarbazone in phase I clinical trial. However, the effects of metal complexation (a main characteristic of thiosemicarbazones) and acquired resistance mechanisms are widely unknown. Therefore, in this study, the copper and iron complexes of COTI-2 were synthesized and evaluated for their anticancer activity and impact on drug resistance in comparison to metal-free thiosemicarbazones. Investigations using Triapine-resistant SW480/Tria and newly established COTI-2-resistant SW480/Coti cells revealed distinct structure-activity relationships. SW480/Coti cells were found to overexpress ABCC1, and COTI-2 being a substrate for this efflux pump. This was unexpected, as ABCC1 has strong selectivity for glutathione adducts. The recognition by ABCC1 could be explained by the reduction kinetics of a ternary Cu-COTI-2 complex with glutathione. Thus, only thiosemicarbazones forming stable, nonreducible copper(II)-glutathione adducts are recognized and, in turn, effluxed by ABCC1. This reveals a crucial connection between copper complex chemistry, glutathione interaction, and the resistance profile of clinically relevant thiosemicarbazones.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jmedchem.0c01277DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7706001PMC
November 2020

Complex formation and cytotoxicity of Triapine derivatives: a comparative solution study on the effect of the chalcogen atom and NH-methylation.

Dalton Trans 2020 Dec;49(46):16887-16902

Department of Inorganic and Analytical Chemistry, Interdisciplinary Excellence Centre, University of Szeged, Dóm tér 7, H-6720 Szeged, Hungary.

α-N-Heterocyclic thiosemicarbazones are an important class of investigational anticancer drugs. The most prominent representative is 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine), which has shown promising results in clinical trials and is currently evaluated in phase III. In this study, we investigated the influence of a chalcogen atom exchange from S (Triapine) to O (O-Triapine) and Se (Se-Triapine) and the methylation of the hydrazonic NH moiety (Me-Triapine) on their complexation with Fe(ii), Fe(iii) and Cu(ii) ions and their cytotoxicity. The main aim of this study was to characterize and compare the most feasible chemical forms in solution, their stability and redox properties, as well as to reveal the relationships of the solution speciation and kinetic data with cytotoxic activity. The complex equilibria and redox properties of the complexes were characterized by the combined use of pH-potentiometry, UV-visible spectrophotometry, electron paramagnetic resonance spectroscopy, and cyclic voltammetry. These revealed that Se-Triapine forms Cu(ii) complexes with higher, and O-Triapine with lower stability as compared with Triapine. Me-Triapine, which is not able to coordinate via the typical (N,N,S-) donor set, nevertheless coordinates to Cu(ii) with unexpected high stability. The Cu(ii) complexes of Se-Triapine and Me-Triapine can be relatively slowly reduced by glutathione at pH 7.4 (but not by ascorbate), similarly to Cu(ii)-Triapine. In contrast, the Cu(ii)-O-Triapine complex can be reduced by both reducing agents in rapid redox reactions. Se-Triapine and Triapine form high stability complexes with both Fe(ii) and Fe(iii) ions, while O-Triapine has a much stronger preference towards Fe(iii) and Me-Triapine towards Fe(ii). This difference in the iron preference of the ligands seems to have a strong impact on their cytotoxic effects, which was measured in a human uterine sarcoma cell line (MES-SA) and its multidrug-resistant subline (MES-SA/Dx5). The Cu(ii) complexes of these calcogensemicarbazones are moderately toxic, and the highest level of ROS generation was found for the Cu(ii) complex of O-Triapine, which is the most reducible.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0dt03465gDOI Listing
December 2020

An ICP-MS-based assay for characterization of gold nanoparticles with potential biomedical use.

Anal Biochem 2020 12 4;611:114003. Epub 2020 Nov 4.

Vernadsky Institute of Geochemistry and Analytical Chemistry, 119991, Moscow, Russian Federation. Electronic address:

Most of potential diagnostic and therapeutic nanoparticles fail to reach clinical trials because assessment of their 'drug-like' properties is often overlooked during the discovery stage. This compromises the results of cell culture and animal experiments, making them insufficient to evaluate the lead candidates for testing on patients. In this study, we demonstrate the potential of high-resolution inductively coupled plasma mass spectrometry (ICP-MS) as a nanoparticle qualification tool. Using novel gold nanoparticles stabilized by N-heterocyclic carbenes as test nanoparticles, it was shown that important prerequisites for biomedical applications, such as resistance to the action of human serum milieu or reactivity toward serum biomolecules, can be reliably assessed by recording the signals of gold or sulfur isotopes. Implemented during the screening stage, the method would provide benefits in shortening timelines and reducing cost for selection and initial testing of medicinal nanoparticle candidates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ab.2020.114003DOI Listing
December 2020

Introducing -, -, and -donor leaving groups: an investigation of the chemical and biological properties of ruthenium, rhodium and iridium thiopyridone piano stool complexes.

Dalton Trans 2020 Nov;49(44):15693-15711

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria. and Research Cluster "Translational Cancer Therapy Research", Waehringer Strasse 42, 1090 Vienna, Austria.

A series of 15 piano-stool complexes featuring either a RuII, RhIII or IrIII metal center, a bidentate thiopyridone ligand, and different leaving groups was synthesized. The leaving groups were selected in order to cover a broad range of different donor atoms. Thus, 1-methylimidazole served as a N-donor, 1,3,5-triaza-7-phosphaadamantane (pta) as a P-donor, and thiourea as a S-donor. Additionally, three complexes featuring different halido leaving groups (Cl, Br, I) were added. Leaving group alterations were carried out with respect to a possible influence on pharmacokinetic and pharmacodynamic parameters, as well as the cytotoxicity of the respective compounds. The complexes were characterized via NMR spectroscopy, X-ray diffraction (where possible), mass spectrometry, and elemental analysis. Cytotoxicity was assessed in 2D cultures of human cancer cell lines by microculture and clonogenic assays as well as in multicellular tumor spheroids. Furthermore, cellular accumulation studies, flow-cytometric apoptosis and ROS assays, DNA plasmid assays, and laser ablation ICP-MS studies for analyzing the distribution in sections of multicellular tumor spheroids were conducted. This work demonstrates the importance of investigating each piano-stool complexes' properties, as the most promising candidates showed advantages over each other in certain tests/assays. Thus, it was not possible to single out one lead compound, but rather a group of complexes with enhanced cytotoxicity and activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0dt03165hDOI Listing
November 2020

Synthetically Versatile Nitrogen Acyclic Carbene Stabilized Gold Nanoparticles.

Chemistry 2020 Dec 18;26(68):15859-15862. Epub 2020 Nov 18.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, 1090, Vienna, Austria.

N-heterocyclic carbenes (NHCs) have received significant attention as gold nanoparticle stabilizers due to their strong binding affinity towards gold. However, their tunability is limited by the difficulty in obtaining nonsymmetric NHCs. In this regard, N-acyclic carbenes (NACs) are attractive alternatives due to their high synthetic versatility, allowing easy tuning of their steric and electronic properties towards specific applications. This work reports the first series of stable and monodisperse NAC-functionalized gold nanoparticles. These particles with sizes ranging 3.8 to 11.6 nm were characterized using NMR, UV/Vis and TEM. The nanoparticles display good stability at elevated temperatures and for extended periods both dried or dispersed in a medium, as well as in the presence of exogenous thiols. Importantly, these NAC-stabilized gold nanoparticles offer a promising and versatile alternative to NHC-stabilized gold nanoparticles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.202003679DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894353PMC
December 2020

Improving the Stability of Maleimide-Thiol Conjugation for Drug Targeting.

Chemistry 2020 Dec 27;26(68):15867-15870. Epub 2020 Oct 27.

Faculty of Chemistry, Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090, Vienna, Austria.

Maleimides are essential compounds for drug conjugation reactions via thiols to antibodies, peptides and other targeting units. However, one main drawback is the occurrence of thiol exchange reactions with, for example, glutathione resulting in loss of the targeting ability. A new strategy to overcome such retro-Michael exchange processes of maleimide-thiol conjugates by stabilization of the thiosuccinimide via a transcyclization reaction is presented. This reaction enables the straightforward synthesis of stable maleimide-thiol adducts essential in drug-conjugation applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.202003951DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7756610PMC
December 2020

Aluminum in Coffee.

ACS Omega 2020 Jun 15;5(25):15335-15343. Epub 2020 Jun 15.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria.

This study investigated the aluminum content in one of the most consumed daily beverages: coffee. The total Al concentration in 10 different samples of coffee beans and their water-extractable fraction were determined. We then tested the influence of different brewing methods on the concentration of the extracted Al in the final beverage. Metal analyses were performed using graphite furnace atomic absorption spectroscopy (GF-AAS) after microwave-assisted acid digestion. The results showed highly variable Al contents in coffee beans (1.5-15.5 mg kg), of which ∼2-10% were water-extractable. The brewing technique had a major influence on the Al content in the beverage: significantly higher Al concentrations (72.57 ± 23.96 μg L) occurred in coffee brewed in an aluminum moka pot. Interestingly, using ground coffee with this method even reduced the Al content in the final beverage compared to the brewing water used. Coffee brewed from Al capsules did not contain significantly higher Al concentrations compared to other methods.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsomega.0c01410DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7331030PMC
June 2020

High Copper Complex Stability and Slow Reduction Kinetics as Key Parameters for Improved Activity, Paraptosis Induction, and Impact on Drug-Resistant Cells of Anticancer Thiosemicarbazones.

Antioxid Redox Signal 2020 08 9;33(6):395-414. Epub 2020 Jun 9.

Institute of Cancer Research, Medical University of Vienna, Vienna, Austria.

Due to their significant biological activity, thiosemicarbazones (TSCs) are promising candidates for anticancer therapy. In part, the efficacy of TSCs is linked to their ability to chelate essential metal ions such as copper and iron. Triapine, the best-studied anticancer TSC, has been tested clinically with promising results in hematological diseases. During the past few years, a novel subclass of TSCs with improved anticancer activity was found to induce paraptosis, a recently characterized form of cell death. The aim of this study was to identify structural and chemical properties associated with anticancer activity and paraptosis induction of TSCs. When testing a panel of structurally related TSCs, compounds with nanomolar anticancer activity and paraptosis-inducing properties showed higher copper(II) complex solution stability and a slower reduction rate, which resulted in reduced redox activity. In contrast, TSCs with lower anticancer activity induced higher levels of superoxide that rapidly stimulated superoxide dismutase expression in treated cells, effectively protecting the cells from drug-induced redox stress. Consequently, we hypothesize that in the case of close Triapine derivatives, intracellular reduction leads to rapid dissociation of intracellularly formed copper complexes. In contrast, TSCs characterized by highly stable, slowly reducible copper(II) complexes are able to reach new intracellular targets such as the endoplasmic reticulum-resident protein disulfide isomerase. The additional modes of actions observed with highly active TSC derivatives are based on intracellular formation of stable copper complexes, offering a new approach to combat (drug-resistant) cancer cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/ars.2019.7854DOI Listing
August 2020

Investigations on the Anticancer Potential of Benzothiazole-Based Metallacycles.

Front Chem 2020 3;8:209. Epub 2020 Apr 3.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria.

A series of 2-phenylbenzothiazole derivatives and their corresponding organometallic ruthenium(II) and osmium(II) complexes were synthesized, designed to exploit both, the attributes of the half-sandwich transition metal scaffold and the bioactivity spectrum of the applied 2-phenylbenzothiazoles. All synthesized compounds were characterized via standard analytical methods. The obtained organometallics showed antiproliferative activity in the low μM range and are thus at least an order of magnitude more potent than the free ligands. ESI-MS measurements showed that the examined compounds were stable in aqueous solution over 48 h. Additionally, their binding preferences to small biomolecules, their cellular accumulation and capacity of inducing apoptosis/necrosis were investigated. Based on the fluorescence properties of the selected ligand and the corresponding ruthenium complex, their subcellular distribution was studied by fluorescence microscopy, revealing a high degree of colocalization with acidic organelles of cancer cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fchem.2020.00209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7147246PMC
April 2020

Development and biological investigations of hypoxia-sensitive prodrugs of the tyrosine kinase inhibitor crizotinib.

Bioorg Chem 2020 06 20;99:103778. Epub 2020 Mar 20.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria; Research Cluster ''Translational Cancer Therapy Research'', Vienna, Austria. Electronic address:

Despite the huge success of tyrosine kinase inhibitors as anticancer agents, severe side effects are a major problem. In order to overcome this drawback, the first hypoxia-activatable 2-nitroimidazole-based prodrugs of the clinically approved ALK and c-MET inhibitor crizotinib were developed. The 2-aminopyridine functionality of crizotinib (essential for target kinase binding) was considered as ideal position for prodrug derivatization. Consequently, two different prodrugs were synthesized with the nitroimidazole unit attached to crizotinib either via carbamoylation (A) or alkylation (B) of the 2-aminopyridine moiety. The successful prodrug design could be proven by docking studies and a dramatically reduced ALK and c-MET kinase-inhibitory potential. Furthermore, the prodrugs showed high stability in serum and release of crizotinib in an enzymatic nitroreductase-based cleavage assay was observed for prodrug A. The in vitro activity of both prodrugs was investigated against ALK- and c-MET-dependent or -overexpressing cells, revealing a distinct hypoxia-dependent activation for prodrug A. Finally, inhibition of c-MET phosphorylation and cell proliferation could also be proven in vivo. In summary of the theoretical, chemical and biological studies, prodrug derivatization of the 2-aminopyridine position can be considered as a promising strategy to reduce the side effects and improve the anticancer activity of crizotinib.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bioorg.2020.103778DOI Listing
June 2020

How versatile is the use of ultrafiltration to study biointeractions of therapeutic metallodrugs?

Anal Biochem 2020 06 26;598:113697. Epub 2020 Mar 26.

Institute of Inorganic Chemistry, University of Vienna, Waehringer Str. 42, A-1090, Vienna, Austria.

For a representative number of approved or investigational anticancer metallodrugs varying in lipophilicity, unspecific adsorption onto ultracentrifugal filter units was studied. It was found that for fairly hydrophilic compounds, such as cisplatin and oxaliplatin, the binding to filters does not substantially affect their amount measured (by ICP-MS) after ultrafiltration (>95%). In the case of metal complexes with moderate lipophilicity (log P > -0.1), adsorption effects turn out to be substantial. This might impede using ultrafiltration for studying the transformations of such drugs in human serum, unless they are rapidly converted into the protein adducts. The adsorption-suppressing effect of proteins was proved for indazolium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] whose recovery from the filters was 61 and 14% in free and HSA-bound form, respectively.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ab.2020.113697DOI Listing
June 2020

Biological evaluation of novel thiomaltol-based organometallic complexes as topoisomerase IIα inhibitors.

J Biol Inorg Chem 2020 05 19;25(3):451-465. Epub 2020 Mar 19.

Faculty of Chemistry, Institute of Inorganic Chemistry, University of Vienna, Vienna, Austria.

Topoisomerase IIα (topo2α) is an essential nuclear enzyme involved in DNA replication, transcription, recombination, chromosome condensation, and highly expressed in many tumors. Thus, topo2α-targeting has become a very efficient and well-established anticancer strategy. Herein, we investigate the cytotoxic and DNA-damaging activity of thiomaltol-containing ruthenium-, osmium-, rhodium- and iridium-based organometallic complexes in human mammary carcinoma cell lines by means of several biological assays, including knockdown of topo2α expression levels by RNA interference. Results suggest that inhibition of topo2α is a key process in the cytotoxic mechanism for some of the compounds, whereas direct induction of DNA double-strand breaks or other DNA damage is mostly rather minor. In addition, molecular modeling studies performed for two of the compounds (with Ru(II) as the metal center) evinces that these complexes are able to access the DNA-binding pocket of the enzyme, where the hydrophilic environment favors the interaction with highly polar complexes. These findings substantiate the potential of these compounds for application as antitumor metallopharmaceuticals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00775-020-01775-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7186247PMC
May 2020

Reactive Oxygen Species (ROS)-Sensitive Prodrugs of the Tyrosine Kinase Inhibitor Crizotinib.

Molecules 2020 Mar 4;25(5). Epub 2020 Mar 4.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria.

Tyrosine kinase inhibitors revolutionized cancer therapy but still evoke strong adverse effects that can dramatically reduce patients' quality of life. One possibility to enhance drug safety is the exploitation of prodrug strategies to selectively activate a drug inside the tumor tissue. In this study, we designed a prodrug strategy for the approved c-MET, ALK, and ROS1 tyrosine kinase inhibitor crizotinib. Therefore, a boronic-acid trigger moiety was attached to the 2-aminopyridine group of crizotinib, which is a crucial position for target kinase binding. The influence of the modifications on the c-MET- and ALK-binding ability was investigated by docking studies, and the strongly reduced interactions could be confirmed by cell-free kinase inhibition assay. Furthermore, the newly synthesized compounds were tested for their activation behavior with HO and their stability in cell culture medium and serum. Finally, the biological activity of the prodrugs was investigated in three cancer cell lines and revealed a good correlation between activity and intrinsic HO levels of the cells for prodrug . Furthermore, the activity of this prodrug was distinctly reduced in a non-malignant, c-MET expressing human lung fibroblast (HLF) cell line.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/molecules25051149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7179202PMC
March 2020

Tetra-(-tolyl)antimony(III)-Containing Heteropolytungstates, [{(-tolyl)Sb}(-α-XWO)] (X = P, As, or Ge): Synthesis, Structure, and Study of Antibacterial and Antitumor Activity.

Inorg Chem 2020 Mar 10;59(5):2978-2987. Epub 2020 Feb 10.

Department of Life Sciences and Chemistry, Jacobs University, 28759 Bremen, Germany.

We have synthesized and structurally characterized three tetra-(-tolyl)antimony(III)-containing heteropolytungstates, [{(-tolyl)Sb}(-α-XWO)] [X = P (), As (), or Ge ()], in aqueous solution using conventional, one-pot procedures. The polyanions , , and were fully characterized in the solid state and in solution and were shown to be soluble and stable in aqueous medium at pH 7. Biological studies demonstrated that all three polyanions possess significant antibacterial and antitumor activities. The minimum inhibitory concentrations of , , and were determined against four kinds of bacteria, including the two pathogenic bacteria strains, and . The three novel polyanions also showed high cytotoxic potency in the human cell lines A549 (non-small cell lung cancer), CH1/PA-1 (ovarian teratocarcinoma), and SW480 (colon carcinoma).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.inorgchem.9b03322DOI Listing
March 2020

Synthesis, Modification, and Biological Evaluation of a Library of Novel Water-Soluble Thiopyridone-Based Organometallic Complexes and Their Unexpected (Biological) Behavior.

Chemistry 2020 Apr 6;26(24):5419-5433. Epub 2020 Apr 6.

Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Waehringer Strasse 42, 1090, Vienna, Austria.

A series of 16 dinuclear thiopyridone-based organometallics with excellent water solubility, increased stability and remarkable cytotoxicity were synthesized and characterized. The complexes of this work formed dimeric species featuring a double positive charge in polar protic solvents, accounting for their outstanding solubility in aqueous solution. Most of them displayed higher antiproliferative activity than their parental thiomaltol complex, with unexpected cytotoxicity trends depending on the employed metal center, ligand modification, and cell line. Insights into their behavior in biological systems were gathered by means of amino-acid interaction studies, cytotoxicity tests in 3D spheroid models, laser ablation, cellular accumulation measurements, as well as cell cycle experiments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.201905546DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7217150PMC
April 2020

Novel phthiocol-based organometallics with tridentate coordination motif and their unexpected cytotoxic behaviour.

Dalton Trans 2020 Feb;49(5):1393-1397

University of Vienna, Faculty of Chemistry, Institute of Inorganic Chemistry, Waehringer Str. 42, A-1090 Vienna, Austria.

Novel phthiocol-based organometallics with in situ formed tridentate N,O,O-coordination motif were established via three-component microwave assisted one-pot reaction. These complexes exhibited enhanced stability in aqueous solution compared to the parental compound KP2048 and showed unexpected cytotoxic behaviour and selectivity in 2D and 3D cell cultures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9dt04462kDOI Listing
February 2020

The Challenge of Classifying Metastatic Cell Properties by Molecular Profiling Exemplified with Cutaneous Melanoma Cells and Their Cerebral Metastasis from Patient Derived Mouse Xenografts.

Mol Cell Proteomics 2020 03 31;19(3):478-489. Epub 2019 Dec 31.

Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna; Joint Metabolome Facility, Faculty of Chemistry, University of Vienna. Electronic address:

The prediction of metastatic properties from molecular analyses still poses a major challenge. Here we aimed at the classification of metastasis-related cell properties by proteome profiling making use of cutaneous and brain-metastasizing variants from single melanomas sharing the same genetic ancestry. Previous experiments demonstrated that cultured cells derived from these xenografted variants maintain a stable phenotype associated with a differential metastatic behavior: The brain metastasizing variants produce more spontaneous micro-metastases than the corresponding cutaneous variants. Four corresponding pairs of cutaneous and metastatic cells were obtained from four individual patients, resulting in eight cell-lines presently investigated. Label free proteome profiling revealed significant differences between corresponding pairs of cutaneous and cerebellar metastases from the same patient. Indeed, each brain metastasizing variant expressed several apparently metastasis-associated proteomic alterations as compared with the corresponding cutaneous variant. Among the differentially expressed proteins we identified cell adhesion molecules, immune regulators, epithelial to mesenchymal transition markers, stem cell markers, redox regulators and cytokines. Similar results were observed regarding eicosanoids, considered relevant for metastasis, such as PGE2 and 12-HETE. Multiparametric morphological analysis of cells also revealed no characteristic alterations associated with the cutaneous and brain metastasis variants. However, no correct classification regarding metastatic potential was yet possible with the present data. We thus concluded that molecular profiling is able to classify cells according to known functional categories but is not yet able to predict relevant cell properties emerging from networks consisting of many interconnected molecules. The presently observed broad diversity of molecular patterns, irrespective of restricting to one tumor type and two main classes of metastasis, highlights the important need to develop meta-analysis strategies to predict cell properties from molecular profiling data. Such base knowledge will greatly support future individualized precision medicine approaches.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/mcp.RA119.001886DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7050108PMC
March 2020

Single Spheroid Metabolomics: Optimizing Sample Preparation of Three-Dimensional Multicellular Tumor Spheroids.

Metabolites 2019 Dec 14;9(12). Epub 2019 Dec 14.

Institute of Analytical Chemistry, University of Vienna, Währinger Str. 38, 1090 Vienna, Austria.

Tumor spheroids are important model systems due to the capability of capturing in vivo tumor complexity. In this work, the experimental design of metabolomics workflows using three-dimensional multicellular tumor spheroid (3D MTS) models is addressed. Non-scaffold based cultures of the HCT116 colon carcinoma cell line delivered highly reproducible MTSs with regard to size and other key parameters (such as protein content and fraction of viable cells) as a prerequisite. Carefully optimizing the multiple steps of sample preparation, the developed procedure enabled us to probe the metabolome of single MTSs (diameter range 790 ± 22 µm) in a highly repeatable manner at a considerable throughput. The final protocol consisted of rapid washing of the spheroids on the cultivation plate, followed by cold methanol extraction. C enriched internal standards, added upon extraction, were key to obtaining the excellent analytical figures of merit. Targeted metabolomics provided absolute concentrations with average biological repeatabilities of <20% probing MTSs individually. In a proof of principle study, MTSs were exposed to two metal-based anticancer drugs, oxaliplatin and the investigational anticancer drug KP1339 (sodium -[tetrachloridobis(1-indazole)ruthenate(III)]), which exhibit distinctly different modes of action. This difference could be recapitulated in individual metabolic shifts observed from replicate single MTSs. Therefore, biological variation among single spheroids can be assessed using the presented analytical strategy, applicable for in-depth anticancer drug metabolite profiling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/metabo9120304DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950217PMC
December 2019