Cellular accumulation and DNA interaction studies of cytotoxic trans-platinum anticancer compounds

The Fundamental Role of Oxime and Oxime Ether Moieties in Improving the Physicochemical and Anticancer Properties of Structurally Diverse Scaffolds

The present review explores the critical role of oxime and oxime ether moieties in enhancing the physicochemical and anticancer properties of structurally diverse molecular frameworks. Specific examples are carefully selected to illustrate the distinct contributions of these functional groups to general strategies for molecular design, modulation of biological activities, computational modeling, and structure-activity relationship studies. An extensive literature search was conducted across three databases, including PubMed, Google Scholar, and Scifinder, enabling us to create one of the most comprehensive overviews of how oximes and oxime ethers impact antitumor activities within a wide range of structural frameworks. This search focused on various combinations of keywords or their synonyms, related to the anticancer activity of oximes and oxime ethers, structure-activity relationships, mechanism of action, as well as molecular dynamics and docking studies. Each article was evaluated based on its scientific merit and the depth of the study, resulting in 268 cited references and more than 336 illustrative chemical structures carefully selected to support this analysis. As many previous reviews focus on one subclass of this extensive family of compounds, this report represents one of the rare and fully comprehensive assessments of the anticancer potential of this group of molecules across diverse molecular scaffolds.

Phosphorus-nitrogen compounds. Part 58. Syntheses, structural characterizations and biological activities of 4-fluorobenzyl-spiro(N/O)cyclotriphosphazene derivatives

The starting compound, tetrachloro-4-fluorobenzyl-spiro(N/O)cyclotriphosphazene (2), was synthesized from the substitution reaction of hexachlorocyclotriphosphazatriene (N₃P₃Cl₆; trimer; HCCP) with sodium 3-(4-fluorobenzylamino)-1-propanoxide (1). Reactions of spiro (2) with excess 1-(2-aminoethyl)-piperidine, 4-(2-aminoethyl)-morpholine, 1-(2-hydroxyethyl)piperidine and 4-(2-aminoethyl)morpholine yielded the fully substituted cyclotriphosphazene derivatives (2a-2d), respectively. Elemental analysis, mass spectrometry (ESI-MS), FTIR, ¹H-, ¹³C- and ³¹P-NMR data confirmed the structure of the new cyclotriphosphazenes (2a-2d); and the crystal structure of 2 was also identified by X-ray crystallography. The quantum mechanical DFT calculations of 2 were performed to estimate the geometry optimization, total energy, orientation of frontier molecular orbitals (HOMOs and LUMOs), and chemical parameters. In addition, antibacterial and antifungal activities of the fully substituted 4-fluorobenzyl-spiro(N/O)cyclotriphosphazenes (2a-2d) were investigated against G(+) and G(-) bacteria and fungi. Using agarose gel electrophoresis, the DNA cleavage activities of these phosphazenes on double-stranded plasmid DNA were evaluated. To evaluate the abilities of compounds 2a-2d to inhibit cell proliferation in different concentrations, the antiproliferative and antimigrative activities against prostate adenocarcinoma (PC3), breast cancer (MCF7) and colon cancer (HT29) cell lines were studied in vitro; and the compound 2c was determined to be the most efficient against the three cancer cells.Communicated by Ramaswamy H. Sarma.

Stereoselective synthesis of oxime containing Pd(II) compounds: Highly effective, selective and stereo-regulated cytotoxicity against carcinogenic PC-3 cells

New palladium compounds [Pd{(1S,4R)-NOH^NH(R)}Cl2] (R = Ph 1a or Bn 1b), [Pd{(1S,4R)-NOH^NH(R)}{(1S,4R)-NO^NH(R)}][Cl] (R = Ph 2a or Bn 2b) and corresponding [Pd{(1R,4S)-NOH^NH(R)}Cl2] (R = Ph 1a’ or Bn 1b’) and...

Antibacterial activities and DNA-cleavage properties of novel fluorescent imidazo-phenanthroline derivatives

Design and biological activities of fluorescent imidazo-phenanthroline derivatives; (E)-5-((4-((4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenoxy)methyl)benzylidene)amino)- isophthalicacid, 2 and 2-(4-(((5-chloroquinolin-8-yl)oxy)methyl)phenyl)-1H-imidazo[4,5f] [1,10]phenanthroline, 3, have been reported. Their characterizations were performed by spectroscopic techniques. Their promising photophysical behaviours were observed in absorbance and fluorescence studies. The antibacterial activities of the compounds were determined against seven different microorganisms; Bacillus subtilis ATCC 6633(G + ), Pseudomonas aeruginosa ATCC 29853(G-), Escherichia coli ATCC 35,218 (G-), Enterococcus faecalis ATCC 292,112 (G + ), Salmonella typhimurium ST-10 (G-), Streptococcus mutans NCTC 10,449 (G + ), and Staphylococcus aureus ATCC 25923(G + ). MIC values of 3 was determined as 156,25 μM on all tested bacteria. A preliminary study of the structure-activity relationship (SAR) also revealed that the antimicrobial activity depended on the substituents on the phenyl ring. The electron withdrawing Cl-substitued compound 3 most favour for antimicrobial activity even at lowest concentration compared to other compounds. DNA-cleavage activities of the compounds were also investigated. The interactions of the compounds with supercoiled pBR322 plasmid DNA were obtained by agarose gel electrophoresis. All imidazo-phenanthroline derivatives were found to be highly effective on DNA, even at the lowest concentrations because of their planar nature which provides ease of bind to the helix structure of DNA.

Synthesis and spectroscopic properties of (N/O) mono- and dispirocyclotriphosphazene derivatives with benzyl pendant arms: study of biological activity

The Cl replacement reactions of hexachlorocyclotriphosphazene (trimer; N 3 P 3 Cl 6 ) with sodium (N-benzyl)- aminopropanoxides (1 and 2) produced monospiro- (3 and 4), cis-, and trans-dispirocyclotriphosphazenes (13-16). The monospiro tetrakis-aminocyclotriphosphazenes (5-12) were obtained by the Cl substitutions of 3 and 4 with different secondary amines. The cis- (13 and 14) and trans-dispirophosphazenes (15 and 16) possessed 2 chiral P centers, and they were able to present meso and racemic forms, respectively. Moreover, the structures of compounds 5 and 14 were designated using X-ray data. The absolute configuration of compound 14 was found as SR in the solid state. Analytical and spectroscopic data of the phosphazenes were consistent with their suggested structures. Antimicrobial activities of the benzyl-pendant-armed cyclotriphosphazenes were scrutinized against G(+) and G(-) bacteria and yeast strains. The bacterium most affected by the synthesized compounds was Pseudomonas aeruginosa . Minimum inhibitory concentrations and minimal bacterial concentrations were in the range of 125-500 μM. Interactions between the phosphazenes (3-12 and 15) and plasmid DNA were studied with agarose gel electrophoresis. The phosphazene- DNA interaction studies of the cyclotriphosphazenes revealed that phosphazenes 3, 4, and 15 had a substantial effect on supercoiled DNA by cleavage of the double helix.

Water soluble, optically active monofunctional Pd(ii) and Pt(ii) compounds: promising adhesive and antimigratory effects on human prostate PC-3 cancer cells

Water soluble, enantiomerically pure “rule breakers” Pd(ii) and Pt(ii) compounds with promising anticancer potential are reported.

Platinum Complexes Can Bind to Telomeres by Coordination

It is suggested that several compounds, including G-quadruplex ligands, can target telomeres, inducing their uncapping and, ultimately, cell death. However, it has never been demonstrated whether such ligands can bind directly and quantitatively to telomeres. Here, we employed the property of platinum and platinum-G-quadruplex complexes to target G-rich sequences to investigate and quantify their covalent binding to telomeres. Using inductively coupled plasma mass spectrometry, surprisingly, we found that, in cellulo, in the presence of cisplatin, a di-functional platinum complex, telomeric DNA was platinated 13-times less than genomic DNA in cellulo, as compared to in vitro data. On the contrary, the amount of mono-functional platinum complexes (Pt-ttpy and Pt-tpy) bound either to telomeric or to genomic DNA was similar and occurred in a G-quadruplex independent-manner. Importantly, the quantification revealed that the low level of cisplatin bound to telomeric DNA could not be the direct physical cause of TRF2 displacement from telomeres. Altogether, our data suggest that platinum complexes can affect telomeres both directly and indirectly.

Computational investigations of trans‑platinum(II) oxime complexes used as anticancer drug

Some platinum oxime complexes are optimized at HF/CEP-31G level which has been reported as the best level for these type complexes in the gas phase. IR spectrum is calculated and the new scale factor is derived. NMR spectrum is calculated at the same level of theory and examined in detail. Quantum chemical parameters which have been mainly used are investigated and their formulas are given in detail. Additionally, selected quantum chemical parameters of studied complexes are calculated. New theoretical IC₅₀% formulas are derived and biological activity rankings of mentioned complexes are investigated.

Syntheses, spectroscopic and crystallographic characterizations of cis- and trans-dispirocyclic ferrocenylphosphazenes: molecular dockings, cytotoxic and antimicrobial activities

The crystallographic and molecular docking investigations and the determinations of the cytotoxic activities of the dispirocyclic ferrocenylphosphazenes were performed.

In Vitro and in vivo Evaluation of Electrochemotherapy with trans-platinum Analogue trans-[PtCl2(3-Hmpy)2]

Background

Cisplatin is used in cancer therapy, but its side effects and acquired resistance to cisplatin have led to the synthesis and evaluation of new platinum compounds. Recently, the synthesized platinum compound trans-[PtCl₂(3-Hmpy)₂] (3-Hmpy = 3-hydroxymethylpyridine) (compound 2) showed a considerable cytotoxic and antitumour effectiveness. To improve compound 2 cytotoxicity in vitro and antitumour effectiveness in vivo, electroporation was used as drug delivery approach to increase membrane permeability (electrochemotherapy).

Materials and methods

In vitro, survival of sarcoma cells with different intrinsic sensitivity to cisplatin (TBLCl2 sensitive, TBLCl2Pt resistant and SA-1 moderately sensitive) was determined using a clonogenic assay after treatment with compound 2 or cisplatin electrochemotherapy. In vivo, the antitumour effectiveness of electrochemotherapy with compound 2 or cisplatin was evaluated using a tumour growth delay assay. In addition, platinum in the serum, tumours and platinum bound to the DNA in the cells were performed using inductively coupled plasma mass spectrometry.

Results

In vitro, cell survival after treatment with compound 2 electrochemotherapy was significantly decreased in all tested sarcoma cells with different intrinsic sensitivity to cisplatin (TBLCl2 sensitive, TBLCl2Pt resistant and SA-1 moderately sensitive). However, this effect was less pronounced compared to cisplatin. Interestingly, the enhancement factor (5-fold) of compound 2 cytotoxicity was equal in cisplatin-sensitive TBLCl2 and cisplatin-resistant TBLCl2Pt cells. In vivo, the growth delay of subcutaneous tumours after treatment with compound 2 electrochemotherapy was lower compared to cisplatin. The highest antitumour effectiveness after cisplatin or compound 2 electrochemotherapy was obtained in TBLCl2 tumours, resulting in 67% and 11% of tumour cures, respectively. Compound 2 induced significantly smaller loss of animal body weight compared to cisplatin. Furthermore, platinum amounts in tumours after compound 2 or cisplatin electrochemotherapy were approximately 2-fold higher compared to the drug treatment only, and the same increase of platinum bound to DNA was observed.

Conclusions

The obtained results in vitro and in vivo suggest compound 2 as a potential antitumour agent in electrochemotherapy.

Phosphorus–nitrogen compounds. Part 37. Syntheses and structural characterizations, biological activities of mono and bis(4-fluorobenzyl)spirocyclotetraphosphazenes

The syntheses, spectroscopic and crystallographic properties, in vitro cytotoxic and antimicrobial activities of the cyclotetraphosphazenes were investigated.

Platinum(II) Iodido Complexes of 7-Azaindoles with Significant Antiproliferative Effects: An Old Story Revisited with Unexpected Outcomes

A series of platinum(II) diiodido complexes containing 7-azaindole derivatives, having the general formula cis-[PtI₂(naza)₂] (1–8), has been prepared and thoroughly characterized, including X-ray structure analysis of cis-[PtI₂(2Me4Claza)₂]∙DMF (8∙DMF; 2Me4Claza = 2-methyl-4-chloro-7-azaindole). Complexes showed high in vitro cytotoxicity against nine human cancer cell lines (IC₅₀ ranging from 0.4 to 12.8 μM), including the cisplatin-resistant ovarian cancer cell line (A2780R; IC₅₀ = 1.0–3.5 μM). The results of in vivo testing, using the L1210 lymphocytic leukaemia model, at the equimolar doses of Pt with cisplatin (2 mg/kg) confirmed the activity of complex 8 comparable to cisplatin. From the mechanistic point of view, evaluated ex vivo by Western blot analyses on the samples of isolated tumour tissues, the treatment of the animals with complex 8, contrary to cisplatin, decreased the levels of tumour suppressor p53 and increased significantly the amount of intracellular anti-apoptotic protein MCL-1_L (37 kDa). Additionally, the active form of caspase 3 was significantly elevated in the sample of tumour tissues treated with complex 8, indicating that the activation of p53-independent cell-death pathway was initiated. The light and electron microscopy observations of the cancerous tissues revealed necrosis as a dominant mechanism of cell death, followed by scarce signs of apoptosis. The additional results (e.g. in vitro interaction experiments with selected biomolecules, cell cycle perturbations, gel electrophoretic studies on pUC19 plasmid DNA) supported the hypothesis that the complexes might be involved in the mechanism of action quite different from cisplatin.

Linking of Antitumor trans NHC-Pt(II) Complexes to G-Quadruplex DNA Ligand for Telomeric Targeting

G-quadruplex structures (G4) are promising anticancerous targets. A great number of small molecules targeting these structures have already been identified through biophysical methods. In cellulo, some of them are able to target either telomeric DNA and/or some sequences involved in oncogene promotors, both resulting in cancer cell death. However, only a few of them are able to bind to these structures G4 irreversibly. Here we combine within the same molecule the G4-binding agent PDC (pyridodicarboxamide) with a N-heterocyclic carbene-platinum complex NHC-Pt already identified for its antitumor properties. The resulting conjugate platinum complex NHC-Pt-PDC stabilizes strongly G-quadruplex structures in vitro, with affinity slightly affected as compared to PDC. In addition, we show that the new conjugate binds preferentially and irreversibly the quadruplex form of the human telomeric sequence with a profile in a way different from that of NHC-Pt thereby indicating that the platination reaction is oriented by stacking of the PDC moiety onto the G4-structure. In cellulo, NHC-Pt-PDC induces a significant loss of TRF2 from telomeres that is considerably more important than the effect of its two components alone, PDC and NHC-Pt, respectively.

Influence of reducing agents on the cytotoxic activity of platinum(IV) complexes: induction of G2/M arrest, apoptosis and oxidative stress in A2780 and cisplatin resistant A2780cis cell lines

The concept of Pt(IV) prodrug design is one advanced strategy to increase the selectivity for cancer cells and to reduce systemic toxicity in comparison to established platinum-based chemotherapy. Pt(IV) complexes are thought to be activated by reduction via physiological reductants, such as ascorbic acid or glutathione. Nevertheless, only few investigations on the link between the reduction rate, which is influenced by the reductant, and the ligand sphere of the Pt(IV) metal centre have been performed so far. Herein, we investigated a set of Pt(IV) compounds with varying rates of reduction with respect to their cytotoxicity and drug accumulation in A2780 and A2780cis ovarian cancer cell lines, their influence on the cell cycle, efficiency of triggering apoptosis, and ability to interfere with plasmid DNA (pUC19). The effects caused by Pt(IV) compounds were compared without or with extracellularly added ascorbic acid and glutathione (or its precursor N-acetylcysteine) to gain understanding of the impact of increased levels of the reductant on the activity of such complexes. Our results demonstrate that reduction is required prior to plasmid interaction. Furthermore, the rate of reduction is crucial for the efficiency of this set of Pt(IV) compounds. The substances that are reduced least likely showed similar performances, whereas the fastest reducing substance was negatively affected by an increased extracellular level of reducing agents, with reduced cytotoxicity and lower efficiency in inducing apoptosis and G2/M arrest. These results confirm the connection between reduction and activity, and prove the strong impact of the reduction site on the activity of Pt(IV) complexes.

Novel enantiopure cyclopentadienyl Ti(IV) oximato compounds as potential anticancer agents

The synthesis and characterization of new enantiopure cyclopentadienyl titanium oximato compounds (S,R)-[(η(5)-C5H5)Ti{к(2)NO,(R)NH·HCl}Cl2] (R=Ph (phenyl) 1a·HCl, Bn (benzyl) 1b·HCl, 2-pic (2-picolyl) 1c·HCl), (S,R)-[(η(5)-C5H5)TiCl2{к(2)NO,(Ph)NH}] (1a) and (S,R)-[(η(5)-C5H5)2TiCl{к(2)NO,(R)NH}] (R=Ph 2a, Bn 2b, 2-pic 2c), along with studies on their behavior in D2O at different pD values are reported. The structure of previously described ammonium-oxime (2S,5R)-{NOH,(Bn)NH·HCl} (b·HCl) and novel titanium derivative 1a have been determined by single crystal X-ray crystallography. The effect of the compounds on cytotoxicity, cell adhesion and migration of the androgen-independent prostate cancer PC-3 cells has been assessed. Compounds 2b and 2c are more cytotoxic than additive doses of titanocene dichloride and free oxime proligand, probing the synergistic effect of these novel compounds. The cytotoxicity of 2b and 2c has been further evaluated against human renal Caki-1, colon DLD-1 and triple negative breast MDA-MB-231 cancer cell lines. The activity found for 2c on PC-3 and Caki-1 is higher than that of highly active Titanocene Y (bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dichloride), while showing selectivity against renal cancer when compared to a non-tumorigenic human renal (HEK-293T) cell line. Compounds 2b and especially 2c are apoptotic in Caki-1 cancer cell lines. Cell adhesion and wound-healing assays confirmed that derivatives 1c·HCl, 2b and 2c affect the adhesion and migration patterns of the PC-3 cell line. Interactions of the novel compounds with plasmid (pBR322) DNA have also been studied, showing that the oximato Ti(IV) derivatives have a weak or no interaction with DNA at physiological pH.

Phosphorus–nitrogen compounds. Part 36. Syntheses, Langmuir–Blodgett thin films and biological activities of spiro-bino-spiro trimeric phosphazenes

The syntheses, spectroscopic and crystallographic properties, LB films, antimicrobial and cytotoxic activities of spiro-bino-spiro phosphazenes were investigated.

Small-Molecule Bcl2 BH4 Antagonist for Lung Cancer Therapy

The BH4 domain of Bcl2 is required for its antiapoptotic function, thus constituting a promising anticancer target. We identified a small-molecule Bcl2-BH4 domain antagonist, BDA-366, that binds BH4 with high affinity and selectivity. BDA-366-Bcl2 binding induces conformational change in Bcl2 that abrogates its antiapoptotic function, converting it from a survival molecule to a cell death inducer. BDA-366 suppresses growth of lung cancer xenografts derived from cell lines and patient without significant normal tissue toxicity at effective doses. mTOR inhibition upregulates Bcl2 in lung cancer cells and tumor tissues from clinical trial patients. Combined BDA-366 and RAD001 treatment exhibits strong synergy against lung cancer in vivo. Development of this Bcl2-BH4 antagonist may provide a strategy to improve lung cancer outcome.

Hydrogen bonding and anticancer properties of water-soluble chiral p-cymene Ru(II) compounds with amino-oxime ligands

The investigation of the hydrogen-bonding effect on the aggregation tendency of ruthenium compounds [(η⁶-p-cymene)Ru(κNHR,κNOH)Cl]Cl (R = Ph (1a), Bn (1b)) and [(η⁶-p-cymene)Ru(κ²NH(2-pic),κNOH)][PF₆]₂ (1c), [(η⁶-p-cymene)Ru(κNHBn,κNO)Cl] (2b) and [(η⁶-p-cymene)Ru(κNBn,κ²NO)] (3b), has been performed by means of concentration dependence ¹H NMR chemical shifts and DOSY experiments. The synthesis and full characterization of new compounds 1c, [(η⁶-p-cymene)Ru(κNPh,κ²NO)] (3a) and 3b are also reported. The effect of the water soluble ruthenium complexes 1a-1c on cytotoxicity, cell adhesion and cell migration of the androgen-independent prostate cancer PC3 cells have been assessed by MTT, adhesion to type-I-collagen and recovery of monolayer wounds assays, respectively. Interactions of 1a-1c with DNA and human serum albumin have also been studied. Altogether, the properties reported herein suggest that ruthenium compounds 1a-1c have considerable potential as anticancer agents against advanced prostate cancer.

Photocontrolled nitric oxide release from two nitrosylruthenium isomer complexes and their potential biomedical applications

Nitric oxide (NO) has key regulatory roles in various biological and medical processes. The control of its local concentration, which is crucial for obtaining the desired effect, can be achieved with exogenous NO donors. Release of NO from metal-nitrosyl complexes upon exposure to light is a strategy that could allow for the site-specific delivery of the reactive species NO to physiological targets. The photodissociation of NO from two nitrosylruthenium(II) isomer complexes {cis- and trans-[Ru(OAc)(2mqn)(2)NO]} was demonstrated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry spectra, and electron paramagnetic resonance spectra further prove the photoinduced NO release by spin trapping of NO free radicals upon photoirradiation. Real-time NO release was quantitatively measured by electrochemistry with an NO-specific electrode. The quantitative control of NO release from [Ru(OAc)(2mqn)(2)NO] in aqueous solutions was done by photoirradiation at different wavelengths. Both isomers show photoinduced damage on plasmid DNA, but the trans isomer has higher cytotoxicity and photocytotoxicity activity against the HeLa tumor cell line than that of the cis isomer. Nitrosylruthenium(II) complex, with 8-quinolinol derivatives as ligands, has a great potential as a photoactivated NO donor reagent for biomedical applications.

Phosphorus-nitrogen compounds: part 30. Syntheses and structural investigations, antimicrobial and cytotoxic activities and DNA interactions of vanillinato-substituted NN or NO spirocyclic monoferrocenyl cyclotriphosphazenes

The gradual Cl replacement reactions of NN (1-3) or NO spirocyclic monoferrocenyl cyclotriphosphazenes (4 and 5) with the potassium salt of 4-hydroxy-3-methoxybenzaldehyde (potassium vanillinate) resulted in the mono (1a-5a), geminal (gem-1b-5b), non-geminal (cis-5b and trans -1b-4b), tri (1c, 3c-5c) and tetra-vanillinato-substituted phosphazenes (1d-5d). All the phosphazene derivatives have stereogenic P-center(s), except tetra-substituted ones. The vanillinatophosphazenes have reversible voltammograms with one-electron anodic and cathodic peaks which are attributed to ferrocenyl redox probe. The structures of the new phosphazene compounds were determined by FTIR, MS, (1)H, (13)C{(1)H} and (31)P{(1)H} NMR spectral data. The solid-state structure of cis -5b was examined by single-crystal X-ray diffraction techniques. In addition, the compounds were tested in HeLa cancer cell lines using MTT assay. The 12 phosphazene derivatives were screened for antimicrobial activity, and 3c was very effective against S. aureus even at 4.88 µM concentration, taking into account the MIC values. Besides, interactions between the phosphazenes and pBR322 plasmid DNA were also investigated.

Inductively coupled plasma mass spectrometry for metallodrug development: albumin binding and serum distribution of cytotoxic cis- and trans-isomeric platinum(II) complexes

Binding to plasma proteins is one of the major metabolic pathways of metallodrugs. In the case of platinum-based anticancer drugs, it is the interaction with serum albumin that affects most strongly their in vivo behavior. Since both the configuration, i.e. cis-trans-isomerism, and the nature of leaving groups have an effect on the reactivity of Pt(II) coordination compounds toward biomolecules, a set of cis- and trans-configured complexes with halide leaving groups (Cl(-), Br(-), and I(-)) and 2-propanone oxime as carrier ligands was chosen for this study. Binding experiments were performed both with albumin and human serum and the Pt content in ultrafiltrates was quantified using inductively coupled plasma mass spectrometry. In order to shed light on the binding mechanism, the albumin binding constant (KHSA) and the octanol-water partition coefficient (P) were experimentally determined and relationships between log KHSA and log P were explored. The correlation was found significant only for cis-configured platinum complexes (R(2)=0.997 and standard deviation=0.02), indicating a certain contribution of the nonspecific binding which is largely dominated by the lipophilicity of compounds. In contrast, for trans-complexes a specific molecular recognition element plays a significant role. The participation of albumin in drug distribution in blood serum was assessed using an equilibrium distribution model and by comparing the percentage binding in the albumin and serum-protein fractions. Irrespective of the compound polarity, albumin contributes from 85 to 100% to the overall binding in serum.

Capillary electrophoresis based on the nucleic acid detection in the application of cancer diagnosis and therapy

This review focuses on capillary electrophoresis-based nucleic acid detection as it is applied to cancer diagnosis and therapy, and provides an introduction to the drawbacks and future developments of analysis with CE.

Guanidine platinum(II) complexes: synthesis, in vitro antitumor activity, and DNA interactions

The novel guanidine compounds trans-[Pt(NH₂Me)₂{NH=C(NHMe)NR}₂](Cl)₂ (R = NEt₂ [7], NC₅H₁₀ [8]) (trans-7,8) were synthesized by the nucleophilic addition of methylamine to dialkylcyanamide ligands of the push–pull nitrile complexes trans-[PtCl₂(RCN)₂] (R = NEt₂, NC₅H₁₀). In vitro cytotoxicity tests conducted for the entire series of the guanidine complexes, i.e. trans-7,8, the neutral cis- or trans-[PtCl₂{NH=C(NH₂)R}₂] (cis-1–3 and trans-1–3) and the cationic cis- or trans-[Pt(NH₃)₂{NH=C(NH₂)R}₂](Cl)₂ (cis-4–6 and trans-4–6) (R = NMe₂ [1,4], NEt₂ [2,5], NC₅H₁₀ [3,6]) in two human cancer cell lines, CH1 (ovarian carcinoma) and SW480 (colon cancer), confirmed that the cytotoxicity of several trans-configured (trans-3,6) complexes is higher than that of cis-congeners (cis-3,6). Cellular platinum levels were analyzed by inductively coupled plasma mass spectrometry upon treatment of SW480 cells, revealing a dependence of cellular accumulation on the geometrical isomerism and the steric hindrance of the variable substituent R on the guanidine ligand. DNA interactions of selected guanidine complexes were studied in order to find hints for the possible reasons for their different activities. Changes induced to the electrophoretic mobility of a dsDNA plasmid confirmed the potency of the guanidine complexes (e.g. trans-1,3,5,6 and cis-1,3,4) to significantly alter DNA secondary structure, indicating DNA as a possible critical target of these compounds.

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A series of guanidine–Pt(II) complexes was extended with two new compounds.

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Structure–activity relationships were inferred from cell culture studies.

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New examples of active platinum complexes with trans geometry were identified.

Mechanism elucidation of the cis-trans isomerization of an azole ruthenium-nitrosyl complex and its osmium counterpart

Synthesis and X-ray diffraction structures of cis and trans isomers of ruthenium and osmium metal complexes of general formulas (nBu4N)[cis-MCl4(NO)(Hind)], where M = Ru (1) and Os (3), and (nBu4N)[trans-MCl4(NO)(Hind)], where M = Ru (2) and Os (4) and Hind = 1H-indazole are reported. Interconversion between cis and trans isomers at high temperatures (80-130 °C) has been observed and studied by NMR spectroscopy. Kinetic data indicate that isomerizations correspond to reversible first order reactions. The rates of isomerization reactions even at 110 °C are very low with rate constants of 10(-5) s(-1) and 10(-6) s(-1) for ruthenium and osmium complexes, respectively, and the estimated rate constants of isomerization at room temperature are of ca. 10(-10) s(-1). The activation parameters, which have been obtained from fitting the reaction rates at different temperatures to the Eyring equation for ruthenium [ΔH(cis-trans)‡ = 122.8 ± 1.3; ΔH(trans-cis)‡ = 138.8 ± 1.0 kJ/mol; ΔS(cis-trans)‡ = -18.7 ± 3.6; ΔS(trans-cis)‡ = 31.8 ± 2.7 J/(mol·K)] and osmium [ΔH(cis-trans)‡ = 200.7 ± 0.7; ΔH(trans-cis)‡ = 168.2 ± 0.6 kJ/mol; ΔS(cis-trans)‡ = 142.7 ± 8.9; ΔS(trans-cis)‡ = 85.9 ± 3.9 J/(mol·K)] reflect the inertness of these systems. The entropy of activation for the osmium complexes is highly positive and suggests the dissociative mechanism of isomerization. In the case of ruthenium, the activation entropy for the cis to trans isomerization is negative [-18.6 J/(mol·K)], while being positive [31.0 J/(mol·K)] for the trans to cis conversion. The thermodynamic parameters for cis to trans isomerization of [RuCl4(NO)(Hind)]-, viz. ΔH° = 13.5 ± 1.5 kJ/mol and ΔS° = -5.2 ± 3.4 J/(mol·K) indicate the low difference between the energies of cis and trans isomers. The theoretical calculation has been carried out on isomerization of ruthenium complexes with DFT methods. The dissociative, associative, and intramolecular twist isomerization mechanisms have been considered. The value for the activation energy found for the dissociative mechanism is in good agreement with experimental activation enthalpy. Electrochemical investigation provides further evidence for higher reactivity of ruthenium complexes compared to that of osmium counterparts and shows that intramolecular electron transfer reactions do not affect the isomerization process. A dissociative mechanism of cis↔trans isomerization has been proposed for both ruthenium and osmium complexes.

Capillary zone electrophoresis and capillary zone electrophoresis-electrospray ionization mass spectrometry studies on the behavior of anticancer cis- and trans-[dihalidobis(2-propanone oxime)platinum(II)] complexes in aqueous solutions

Anticancer chemotherapeutics with new modes of action are in great demand to overcome adverse effects, resistance problems and a limited application range. Among other approaches, trans-configured analogs of the established chemotherapy drug cisplatin show promising results in biological model systems. Herein we report on comparative studies on the stability of cis- and trans-[dihalidobis(2-propanone oxime)platinum(II)] (halido=Cl(-), Br(-), I(-)) complexes in phosphate buffer, using capillary zone electrophoresis (CZE) and CZE hyphenated to electrospray ionization-mass spectrometry (CZE-ESI-MS). The used conditions simulate those in the cytoplasm, being of importance for the activation of platinum anticancer agents for their reaction with DNA, the ultimate target. The configuration of the Pt center, i.e., cis or trans, accounts for the differing degradation kinetics of the compounds and in addition a significant influence of the halido leaving group was observed, with in case of the cis complexes pseudo first order rate constants of 0.268, 0.191 and 0.142h(-1) for Br(-), Cl(-), and I(-), respectively. Degradation of the trans isomers was significantly faster compared to their cis-configured counterparts also leading to different products which were characterized by hyphenation of CZE to ESI-MS.

Novel oximato-bridged platinum(II) di- and trimer(s): synthetic, structural, and in vitro anticancer activity studies

Novel platinum complexes of trans geometry [PtCl(2){(Z)-R(H)C═NOH}(2)] [R = Me (1), Et (3)] and [PtCl(2){(E)-R(H)C═NOH}{(Z)-R(H)C═NOH}] [R = Me (2), Et (4)] as well as the classic trans-[PtCl(2)(R(2)C═NOH)(2)] [R = Me, Et] were reacted with an equivalent amount of silver acetate in acetone solution at ambient temperature, resulting in formation of unprecedented head-to-tail-oriented oximato-bridged dimers [PtCl{μ-(Z)-R(H)C═NO}{(Z)-R(H)C═NOH}](2) [R = Me (5), Et (7)], [PtCl{μ-(Z)-R(H)C═NO}{(E)-R(H)C═NOH}](2) [R = Me (6), Et (8)], and [PtCl(μ-R(2)C═NO)(R(2)C═NOH)](2) [R = Me (9), Et (10)], correspondingly. The dimeric species feature a unique six-membered diplatinacycle and represent the first example of oxime ligands coordinated to platinum via the oxygen atom. All complexes were characterized by elemental analyses, electrospray ionization mass spectrometry, IR and multinuclear ((1)H, (13)C, and (195)Pt) NMR spectroscopy, as well as X-ray diffraction in the cases of dimers 6 and 9. Furthermore, the crystal and molecular structures of a trimeric oximato-bridged complex 11 comprising three platinum units connected in a chain way were established. The cytotoxicity of both dimers and the respective monomers was comparatively evaluated in three human cancer cell lines: cisplatin-sensitive CH1 cells as well as cisplatin-resistant SW480 and A549 cells, whereupon structure-activity relationships were drawn. Thus, it was found that dimerization results in a substantial (up to 7-fold) improvement of IC(50) values of (aldoxime)Pt(II) compounds, whereas for the analogous complexes featuring ketoxime ligands the reverse trend was observed. Remarkably, the novel dimers yielded no cross-resistance with cisplatin in SW480 cells, exhibiting up to 2-fold enhanced cytotoxicity in comparison with the CH1 cell line and thereby possessing a promising potential to overcome resistance toward platinum anticancer drugs. The latter point was also confirmed by investigating the potency of apoptosis induction in the case of one monomer as well as one dimer; the investigated complexes proved to be strong apoptotic agents which could induce cell death even in the cisplatin-resistant SW480 cell line.