Colour-Tunable Organic Light-Emitting Diodes with Single Pt (O^N^C^N)-dibenzofuran Emitter Exhibiting High External Quantum Efficiency of ∼30% and Superior Operational Lifetime

Colour-tunable organic light-emitting diodes (CT-OLEDs) have a large colour-tuning range, high efficiency and operational stability at practical luminance, making them ideal for human-machine interactive terminals of wearable biomedical devices. However, the device operational lifetime of CT-OLEDs is currently far from reaching practical requirements. To address this problem, we designed a tetradentate Pt(II) complex named tetra-Pt-dbf, which can emit efficiently in both monomer and aggregation states. This emitter has a high Td of 508°C and a large intermolecular bonding energy of -52.0 kcal/mol, which improve its thermal/chemical stability. Our unique single-emitter CT-OLED essentially avoids the "colour-ageing issue" and achieves a large colour-tuning span (red to yellowish green) and a high EQE of ∼30% at 1000 cd m-2 as well as an EQE of above 25% at 10000 cd m-2. We estimated a superior LT90 operational lifetime of 520,536 hours at a functional luminance of 100 cd m-2, which is over 20 times longer than the state-of-the-art CT-OLEDs. To demonstrate the potential application of such OLEDs in wearable biomedical devices, we fabricated a simple electromyography (EMG)-visualization system using our CT-OLEDs. This article is protected by copyright. All rights reserved.

Production and synthesis of a novel 191Pt-labeled platinum complex and evaluation of its biodistribution in healthy mice

We previously reported that our sugar-conjugated platinum complex (cis-dichloro [(2-fluoro-α-d-glucopylanosidyl) propane-1,3-diamine] platinum: FGC-Pt) has low toxicity and tumor growth inhibitory effect comparable to that of cisplatin. We focused on radioactive Pt isotopes in order to analyze the kinetics of FGC-Pt using gamma-ray imaging techniques, assuming that FGC-Pt could be used for chemotherapy in the future. Therefore, in this study, we aimed to develop a non-invasive method to analyze the biodistribution of FGC-Pt using 191Pt-labeled FGC-Pt ([191Pt]FGC-Pt). 191Pt was produced via the (n,2n) reaction induced by accelerator neutrons. [191Pt]FGC-Pt was prepared using two different methods. In the first method, [191Pt]FGC-Pt (method A) was obtained through the accelerator neutron irradiation of FGC-Pt. In the second method, [191Pt]FGC-Pt (method B) was synthesized using [191Pt]K2PtCl4, which was obtained by the accelerator neutron irradiation of K2PtCl4. Highly purified [191Pt]FGC-Pt was obtained using the latter method, which suggests that the synthetic method using a 191Pt-labeled platinum reagent is suitable for the radioactivation of platinum complexes. We also aimed to investigate whether a significant correlation existed between the biodistribution of FGC-Pt and [191Pt]FGC-Pt in healthy mice 24 h after tail vein administration. FGC-Pt and [191Pt]FGC-Pt were similarly distributed in healthy mice, with a higher accumulation in the liver and kidney 24 h post injection. In addition, a significant correlation (p < 0.05, r = 0.92) between the 191Pt radioactivity concentration (%ID/g (gamma counter)) and platinum concentration (%ID/g (ICP-MS)) was observed in 13 organs. These results suggest that 191Pt-labeled compounds, synthesized using radioactive platinum reagents, can be used to confirm the biodistribution of platinum compounds. Our study on the biodistribution of [191Pt]FGC-Pt is expected to contribute to the development of novel platinum-based drugs in the future.

IRMPD spectroscopy and quantum-chemical simulations of the reaction products of cisplatin with the dipeptide CysGly

The inorganic antineoplastic drug cisplatin was made to react in solution with the dipeptide cysteinylglycine (CysGly), chosen as a functional model of glutathione, and the reaction products were analyzed using electrospray ionization mass spectrometry (ESI-MS). Selected complexes, i.e., the primary substitution product cis-[PtCl(NH3)2(CysGly)]+ and the chelate cis-[PtCl(NH3)(CysGly)]+, were submitted to IR multiple photon dissociation (IRMPD) spectroscopy obtaining their vibrational features. The experimental IR ion spectra were compared with the calculated IR absorptions of different plausible isomeric families, finding CysGly to bind preferentially platinum(II) via its deprotonated thiolic group in the monovalent complex, cis-[PtCl(NH3)2(CysGly)]+, and to evolve in the S,N-bound chelate structure cis-[PtCl(NH3)(CysGly)]+ through the SH and NH2 functionality of the cysteine residue. Moreover, our findings indicate that the platination reaction does not affect the CysGly peptide bond, which remains in its trans configuration. These results provide additional insights into the reactivity of Pt(II)-complexes with glutathione which is involved in cellular cisplatin resistance.

Elusive intermediates in cisplatin reaction with target amino acids: Platinum(II)-cysteine complexes assayed by IR ion spectroscopy and DFT calculations

The reactivity of a widely used metal based antineoplastic drug, cisplatin, cis-PtCl₂(NH₃)₂, with L-cysteine (Cys) has been investigated using a combination of electrospray ionization mass spectrometry (ESI-MS), IRMPD gas phase ion spectroscopy and DFT calculations. The cysteine lateral chain represents one of the main platination sites in proteins, which is believed to be related to the resistance mechanisms to cisplatin. The vibrational features of the mass-selected substitution product cis-[PtCl(NH₃)₂(Cys)]⁺ and the intercepted cis-[PtCl(NH₃)₂(H₂O)(Cys)]⁺ intermediate complex were compared to calculated IR spectra, enabling the assessment of the sampled ions structures. In cis-[PtCl(NH₃)₂(Cys)]⁺, cysteine was found to bind platinum through the sulfur atom as a thiolate zwitterion, highlighting the enhanced acidity of the cysteine thiol group upon metal coordination. The cis-[PtCl(NH₃)₂(H₂O)(Cys)]⁺ structure complies with the non-covalent encounter complex, formed by cis-[PtCl(NH₃)₂(H₂O)]⁺ and neutral cysteine. This species is able to undergo the substitution process to produce cis-[PtCl(NH₃)₂(Cys)]⁺ when activated as a mass-isolated ion suggesting its participation in the reaction mechanism of cisplatin with cysteine in solution. Finally, the DFT-calculated energy profile for the substitution reaction was correlated with the peculiar gas-phase reactivity of this non-covalent complex, resulting to be 10-fold less reactive toward substitution than the corresponding methionine complex.

G-quadruplex stabilizer Tetra-Pt(bpy) disrupts telomere maintenance and impairs FAK-mediated migration of telomerase-positive cells

G-quadruplex regulates a wide spectrum of biological processes, including telomere maintenance, DNA replication and transcription. The development of small molecules to selectively target G-quadruplex and their application remain hotspots in cancer therapy. Here, we explored the biological effect of G-quadruplexes stabilizer Tetra-Pt(bpy) in telomerase-positive cancer cells. Telomere maintenance was evaluated by telomerase repeat amplification protocol, chromosome orientation fluorescence in situ hybridization and telomere restriction fragment assays. We found that Tetra-Pt(bpy) accelerates telomere shortening through dual inhibition of telomerase activity and telomere sister chromatin exchanges mediated by telomeric G-quadruplexes. Consequently, Tetra-Pt(bpy)-treated cancer cells became enriched with extremely short telomeres and produced a strong telomeric DNA damage response following long-term treatment, leading to cell proliferation inhibition and senescence. Experimental evidence from RNA seq and cell migration-related assays showed that Tetra-Pt(bpy) decreased cell-matrix adhesion and inhibited the migration of non-senescent tumor cells. Mechanistically, Tetra-Pt(bpy) induced the formation of G-quadruplexes in focal adhesion kinase (FAK)-encoding gene PTK2, resulting in FAK transcription inhibition. Tetra-Pt(bpy) reduced xenograft tumor formation and inhibited tumor cell growth and migration in mice. This study further elucidates the function of G-quadruplexes in the human genome and reveals the potential of Tetra-Pt(bpy) as a novel chemotherapeutic agent for targeting telomerase-positive cancer cells.

Development and evaluation of a theranostic probe with RGD peptide introduced platinum complex to enable tumor-specific accumulation

Cisplatin (CDDP) has been widely used for chemotherapy. However, it has several unfavorable side effects due to its low tumor selectivity. In this study, we designed, synthesized, and evaluated Pt(IV)-[c(RGDyK)]₂ (9), in which two molecules of an RGD peptide are introduced as a carrier molecule to cancer into oxoplatin, a Pt(IV) prodrug of CDDP, to enhance cancer selectivity. Furthermore, we prepared and evaluated Pt(IV)-[c(RGDyK)]{[¹²⁵I]c[RGDy(3-I)K]} ([¹²⁵I]10) for a preliminary step of nuclear medicine imaging and theranostics. Compound 9 inhibited cell growth in the cell viability assay and, [¹²⁵I]10 was highly accumulated in tumor tissues (1 h: 3.53 ± 0.53 %ID/g) in the biodistribution study. These results indicate that implementing RGD peptides into oxoplatin enabled tumor-specific accumulation, and combining [^123/124I]10 and 9 for diagnostic imaging and therapy could be useful for cancer theranostics.

Dual Function of β-hydroxy Dithiocinnamic Esters: RAFT Agent and Ligand for Metal Complexation

The reversible addition-fragmentation chain-transfer (RAFT) process has become a versatile tool for the preparation of defined polymers tolerating a large variety of functional groups. Several dithioesters, trithiocarbonates, xanthates, or dithiocarbamates have been developed as effective chain transfer agents (CTA), but only few examples have been reported, where the resulting end groups are directly considered for a secondary use besides controlling the polymerization. We here demonstrate that β-hydroxy dithiocinnamic esters represent a hitherto overlooked class of materials, which were originally designed for the complexation of transition metals but might as well act as reversible CTA. Modified with a suitable leaving group (R-group), these vinyl conjugated dithioesters indeed provide reasonable control over the polymerization of acrylates, acrylamides, or styrene via the RAFT process. Kinetic studies revealed linear evolutions of molar mass with conversion, while different substituents on the aromatic unit had only a minor influence. Block extensions prove the livingness of the polymer chains, although extended polymerization times may lead to side reactions. The resulting dithiocinnamic ester end groups are still able to form complexes with platinum, which verifies that the structural integrity of the end group is maintained. These findings open a versatile new route to tailor-made polymer bound metal complexes. This article is protected by copyright. All rights reserved.

Affinity variation in the interactions of tryptophan- β-cyclodextrin-platinum complex with G-quadruplex and duplex DNAs

DNA forms non-canonical Guanine-rich-quadruplex structures that play crucial roles such as maintenance of the telomere, transcription, and replication. Selective binding of small molecular ligands to G-quadruplexes and stabilization of them gain importance in the control of cell proliferation and development of therapeutics. In this paper, we report the synthesis of a tryptophan-β-cyclodextrin complex and its platinum complex. The binding interaction of the synthesized Trp-β-CD-Pt compound with various DNAs, including a duplex DNA and three quadruplexes, are investigated. The binding of the compound to quadruplexes shows a general increase in the binding strength compared to the strength of binding with the duplex, CT-DNA. The compound reveals the strongest binding with kit22. An enhancement of fluorescence is generally observed when the ligand binds to all the DNAs, except myc22. The structure of the host: guest complex with Berberine, a model G-quadruplex binding ligand, is investigated using 2 D ROESY spectroscopy. The host: guest binding is strong and the DNA interaction does not extract much of the Berberine molecule from the complex. The differential bindings of the ligand in free- and Berberine-loaded forms with different G-quadruplexes are discussed in detail based on binding strengths and the modulation of fluorescence.Communicated by Ramaswamy H. Sarma.

Assessing Impact of Platinum Complexes on Mitochondrial Functions

Platinum-based antitumor drugs play important roles in the clinical treatment of various tumors. Nevertheless, some deficiencies such as poor targeting ability, low bioavailability, in vivo deactivation, drug resistance, and side effects undermine the efficacy of these drugs. Mitochondria are important organelles which regulate the energy metabolism, physiological function, life span, and survival of the cells. Regulating or interfering with mitochondrial metabolism is of great significance in the prevention or treatment of cancers. Thus, a series of mitochondrion-targeted platinum complexes were prepared by modifying triphenylphosphine (TPP⁺) through chemical modifications, which endow traditional platinum drugs with new properties and mechanisms through interfering with mitochondrial DNA (mtDNA), mitochondrial membrane potential (MMP), mitochondrial morphology, mitochondrial bioenergetics, or production of reactive oxygen species (ROS), thereby opening a new path for the clinical application of platinum drugs. Here we introduce the synthesis of some TPP⁺-modified platinum (II, IV) complexes in details and the detection method of the activity parameters related to the mitochondrial functions.

Functionalized azobenzene platinum(II) complexes as putative anticancer compounds

The synthesis and characterization of four platinum(II) complexes using azobenzenes conveniently functionalized as ligands has been carried out. The characteristic photochemical behavior of the complexes due to the presence of azobenzene-type ligands and the role of the ligands in the activation of the complexes has been studied. Their promising cytotoxicity observed in HeLa cells prompted us to study the mechanism of action of these complexes as cytostatic agents. The interaction of the compounds with DNA, studied by circular dichroism, revealed a differential activity of the Pt(II) complexes upon irradiation. The intercalation abilities of the complexes as well as their reactivity with common proteins present in the blood stream allows to confirm some of the compounds obtained as good anticancer candidates.

Prediction of the hydrophobicity of platinum(IV) complexes based on molecular surface properties

A quantitative structure-property relationship (QSPR) study was performed for predicting the hydrophobicity of Pt(IV) complexes. Two four-parameter equations, one based solely on structural descriptors derived from electrostatic potentials (ESPs) on molecular surface, and the other integrated ESP descriptors with molecular surface area (A_S), were firstly constructed. Mechanistic interpretations of the structural descriptors introduced were elucidated in terms of solute-solvent intermolecular interactions. Subsequently, several up-to-date modeling techniques, including support vector machine (SVM), least-squares support vector machine (LSSVM), random forest (RF) and Gaussian process (GP), were utilized to build the nonlinear models. Systematical validations including leave-one-out cross-validation, the validation for test set, as well as a more rigorous Monte Carlo cross-validation were performed to verify the reliability of the constructed models. The predictive performances of the four different nonlinear modeling methods follow the order of LSSVM≈GP > RF > SVM. The pure-ESP-based models are generally inferior to the A_S-integrated ones. Comparisons with previous results were made.

Diplatin, a novel water-soluble platinum complex, inhibits lung cancer growth via augmentation of Fas-mediated apoptosis

Platinum drugs, such as cisplatin (DDP) and carboplatin (CBP), are the main drugs for the treatment of lung cancer, but their practical clinical application is limited by severe toxicity and acquired drug resistance. Our previous study has indicated that diplatin, [2-(4-(diethyl-amino)butyl)malonate-O,O']-[(1R,2R)-cyclohexane-1,2-diamine N,N'] platinum (II) phosphate, a novel water-soluble platinum complex, could overcome DDP-resistant cells and was less toxic than comparable platinum drugs. In the present study, the effects and mechanisms of diplatin were further evaluated for its development as a novel anti-lung cancer platinum drug. Here, we found diplatin down-regulated the viability of H460 and LTEP-A-2 cells in a dose-dependent manner. Nude mice administrated with diplatin (30-120 mg/kg) via tail vein injection dose-dependently inhibited the growth of H460 and LTEP-A-2 xenograft tumors, whose action mainly correlated with the induction of tumor apoptosis. Particularly, the exposure of lung cancer cells or xenograft tumors to diplatin resulted in elevated Fas level, and knockdown of Fas ameliorated diplatin-induced cells apoptosis. Overall, we suggest that diplatin has potent anti-tumor activity, which probably acts through Fas-mediated signaling pathway.

NF-κB hijacking theranostic Pt(ll) complex in cancer therapy

Platinum complexes have been used for anti-cancer propose for decades, however, their high side effects resulting from damage to healthy cells cannot be neglected and prevent further clinical utilisation. Here, we designed a cyclometalated platinum (II) complex that can bind the endogenous nuclear factor-κB (NF-κB) protein. Employing detailed colocalization studies in co-culture cell line models, we show that by binding to NF-κB, the platinum (II) complex is capable of upregulated nuclear translocation specifically in cancer but not normal cells, thereby impairing cancer proliferation without disturbing healthy cells. In a murine tumour model, the platinum (II) complex prevents tumour growth to a greater extent than cisplatin and with considerably lower side-effects and kidney damage. Considering its weak damage to normal cells combined with high toxicity to cancer cells, this NF-κB-binding platinum complex is a potential anti-cancer candidate and acts to verify the strategy of hijacking endogenous trans-nuclear proteins to achieve cancer-cell specificity and enhance therapeutic indices.

A novel platinum complex containing a piplartine derivative exhibits enhanced cytotoxicity, causes oxidative stress and triggers apoptotic cell death by ERK/p38 pathway in human acute promyelocytic leukemia HL-60 cells

Piplartine (piperlongumine) is a plant-derived compound found in some Piper species that became a novel potential antineoplastic agent. In the present study, we synthesized a novel platinum complex containing a piplartine derivative cis-[PtCl(PIP-OH)(PPh₃)₂]PF₆ (where, PIP-OH = piplartine demethylated derivative; and PPh₃ = triphenylphosphine) with enhanced cytotoxicity in different cancer cells, and investigated its apoptotic action in human promyelocytic leukemia HL-60 cells. The structure of PIP-OH ligand was characterized by X-ray crystallographic analysis and the resulting platinum complex was characterized by infrared, molar conductance measurements, elemental analysis and NMR experiments. We found that the complex is more potent than piplartine in a panel of cancer cell lines. Apoptotic cell morphology, increased internucleosomal DNA fragmentation, without cell membrane permeability, loss of the mitochondrial transmembrane potential, increased phosphatidylserine externalization and caspase-3 activation were observed in complex-treated HL-60 cells. Treatment with the complex also caused a marked increase in the production of reactive oxygen species (ROS), and the pretreatment with N-acetyl-L-cysteine, an antioxidant, reduced the complex-induced apoptosis, indicating activation of ROS-mediated apoptosis pathway. Important, pretreatment with a p38 MAPK inhibitor (PD 169316) and MEK inhibitor (U-0126), known to inhibit ERK1/2 activation, also prevented the complex-induced apoptosis. The complex did not induce DNA intercalation in cell-free DNA assays. In conclusion, the complex exhibits more potent cytotoxicity than piplartine in a panel of different cancer cells and triggers ROS/ERK/p38-mediated apoptosis in HL-60 cells.

Direct measurement of interaction forces between a platinum dichloride complex and DNA molecules

The interaction forces between a platinum dichloride complex and DNA molecules have been studied using atomic force microscopy (AFM). The platinum dichloride complex, di-dimethylsulfoxide-dichloroplatinum (II) (Pt(DMSO)₂Cl₂), was immobilized on an AFM probe by coordinating the platinum to two amino groups to form a complex similar to Pt(en)Cl₂, which is structurally similar to cisplatin. The retraction forces were measured between the platinum complex and DNA molecules immobilized on mica plates using force curve measurements. The histogram of the retraction force for λ-DNA showed several peaks; the unit retraction force was estimated to be 130 pN for a pulling rate of 60 nm/s. The retraction forces were also measured separately for four single-base DNA oligomers (adenine, guanine, thymine, and cytosine). Retraction forces were frequently observed in the force curves for the DNA oligomers of guanine and adenine. For the guanine DNA oligomer, the most frequent retraction force was slightly lower than but very similar to the retraction force for λ-DNA. A higher retraction force was obtained for the adenine DNA oligomer than for the guanine oligomer. This result is consistent with a higher retraction activation energy of adenine with the Pt complex being than that of guanine because the kinetic rate constant for retraction correlates to exp(FΔx - ΔE) where ΔE is an activation energy, F is an applied force, and Δx is a displacement of distance.

Synthesis, properties, antitumor and antibacterial activity of new Pt(II) and Pd(II) complexes with 2,2'-dithiobis(benzothiazole) ligand

Mono- and binuclear Pt(II) and Pd(II) complexes with 2,2'-dithiobis(benzothiazole) (DTBTA) ligand are reported. [Pt(DTBTA)(DMSO)Cl]Cl∙CHCl₃ (1) and [Pd₂(µ-Cl)₂(DTBTA)₂]Cl₂ (2) have been synthesized and structurally characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopy, MS spectrometry and the content of platinum and palladium was determined using a flame atomic spectrometer. Two different coordination modes of 1 and 2 complexes were found; in both complexes, the coordination of Pt(II) and Pd(II) ions involves the N(3) atoms of the ligand but the binuclear complex 2, is a cis-chloro-bridged palladium complex. Evaluation of their in vitro antitumor activity against two human tumor cell lines human breast cancer (MCF-7) and hepatocellular carcinoma (HepG2); and their antimicrobial activity against Escherichia coli and Kokuria rhizophila was performed. Only complex 1 showed a dose- and time-dependent cytotoxic activity against the two tumor cell lines, associated to apoptosis and accumulation of treated cells in G0/G1 phase of cell cycle, while both 1 and 2 exhibited antimicrobial activity with complex 1 much more potent. The study on intracellular uptake in both MCF-7 and HepG2 cell lines revealed that only platinum of complex 1 is present inside the cells, suggesting a different mode of action of the two compounds. This was also in agreement with the results obtained for the antitumor and antibacterial activity.

Anticancer Effects of a New Aminosugar-conjugated Platinum Complex Agent Against Cisplatin-resistant Gastric Cancer

BACKGROUND/AIM

Resistance against cisplatin is a problem for the success of gastric cancer chemotherapy. Herein, we evaluated the antitumor effect of a new aminosugar-conjugated, mono-functional platinum complex (Pt-Oqn), which forms a single covalent bond with DNA.

MATERIALS AND METHODS

We compared the cytotoxicity of Pt-Oqn to that of cisplatin (CDDP), oxaliplatin (L-OHP) and carboplatin (CBDCA). We also compared Pt-Oqn and cisplatin for DNA double-strand breaks based on phosphorylated histone H2AX levels in cancer cells and antitumor effects in xenograft models.

RESULTS

The resistance factor (RF) for Pt-Oqn was low among the four drugs, indicating the potential of Pt-Oqn for overcoming CDDP-induced resistance. In MKN45-R cells, γ-H2AX protein increased following treatment with Pt-Oqn, but not with cisplatin. Finally, Pt-Oqn, but not cisplatin, showed significant antitumor effects in MKN45-R xenografts.

CONCLUSION

This new aminosugar-conjugated platinum complex is a promising candidate agent for overcoming the drug resistance of cisplatin-resistant stomach cancer.

Effects of histidin-2-ylidene vs. imidazol-2-ylidene ligands on the anticancer and antivascular activity of complexes of ruthenium, iridium, platinum, and gold

Couples of N-heterocyclic carbene complexes of ruthenium, iridium, platinum, and gold, each differing only in the carbene ligand being either 1,3-dimethylimidazol-2-ylidene (IM) or 1,3-dimethyl-N-boc-O-methylhistidin-2-ylidene (HIS), were assessed for their antiproliferative effect on seven cancer cell lines, their interaction with DNA, their cell cycle interference, and their vascular disrupting properties. In MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays only the platinum complexes were cytotoxic at single-digit micromolar IC₅₀ concentrations with the (HIS)Pt complex being on average twice as active as the (IM)Pt complex. The former was highly efficacious against cisplatin-resistant HT-29 colon carcinoma cells where the latter had no effect. Both Pt complexes were accumulated by cancer cells and bound to double-helical DNA equally well. Only the (HIS)Pt complex modified the electrophoretic mobility of circular DNA in vitro due to the HIS ligand causing greater morphological changes to the DNA. Both platinum complexes induced accumulation of 518A2 melanoma cells in G2/M and S phase of the cell cycle. A disruption of blood vessels in the chorioallantoic membrane of fertilized chicken eggs was observed for both platinum complexes and the (IM)gold complex. The (HIS)platinum complex was as active as cisplatin in tumor xenografted mice while being tolerated better. We found that the HIS ligand may augment the cytotoxicity of certain antitumoral metal fragments in two ways: by acting as a transmembrane carrier increasing the cellular accumulation of the complex, and by initiating a pronounced distortion and unwinding of DNA. We identified a new (HIS)platinum complex which was highly cytotoxic against cancer cells including cisplatin-resistant ones.

Metalated nucleotide chemisorption on hydroxyapatite

The experiments here reported evidence on the importance of the residual charge of a nucleotide derivative, for the adsorption on nHAP (hydroxyapatite nanocrystals), in water solution. We found that the simple presence of phosphates on the nucleotide derivative does not guarantee adsorption on nHAP. On the other hand, we demonstrated that a cationic or neutral charge on a nucleotide derivative produces a strongly reduced chemical adsorption (chemisorption) whereas, in the presence of a net negative charge, relevant adsorption on nHAP is observed. The number of phosphates can only modulate the adsorption efficiency of a molecule provided that this latter bears an overall negative charge. The neutral zwitterionic nucleotide Pt(II) complexes, bearing negatively charged phosphates, are unable to give stable chemisorption. Previous considerations are important to model the binding ability of phosphate bearing nucleotide derivatives or molecules on hydroxyapatite. The findings reported in the present paper could be relevant in bone tissue targeting or nHAP mediated drug delivery.

Synthesis of a platinum(II) complex with 2-(4-methoxy-phenyl) imidazo [4,5-f]-[1,10] phenanthrolin and study of its antitumor activity

A new platinum(II) complex of [Pt(II)(L) (pn)]Cl·2H2O (1) (pn = 1,3-propanediamine) with 2-(4-methoxy-phenyl)imidazo [4,5-f]-[1,10]phenanthrolin (H-L) was synthesized and characterized. In complex 1, the platinum adopts a four-coordinated square planar geometry. Complex 1 exhibited selective cytotoxicity against NCI-H460, BEL-7402, SK-OV-3, SK-OV-3/DDP and HeLa cell lines with IC50 values in the micromolar range (9.7-35.8 μM), but low cytotoxicity toward normal human liver HL-7702 cells. Complex 1 caused HeLa cell cycle arrest at S phase and it induced HeLa apoptosis by the activation of caspase-3/9. Various experiments showed that complex 1 preferred to bind with G-quadruplex in c-myc. Taken together, we found that complex 1 exerted its antitumor activity mainly via inhibiting telomerase by interaction with c-myc quadruplex and activation of caspase-3/9.

A site-selective, irreversible inhibitor of the DNA replication auxiliary factor proliferating cell nuclear antigen (PCNA)

Proliferating cell nuclear antigen (PCNA) assumes an indispensable role in supporting cellular DNA replication and repair by organizing numerous protein components of these pathways via a common PCNA-interacting sequence motif called a PIP-box. Given the multifunctional nature of PCNA, the selective inhibition of PIP-box-mediated interactions may represent a new strategy for the chemosensitization of cancer cells to existing DNA-directed therapies; however, promiscuous blockage of these interactions may also be universally deleterious. To address these possibilities, we utilized a chemical strategy to irreversibly block PIP-box-mediated interactions. Initially, we identified and validated PCNA methionine 40 (M40) and histidine 44 (H44) as essential residues for PCNA/PIP-box interactions in general and, more specifically, for efficient PCNA loading onto chromatin within cells. Next, we created a novel small molecule incorporating an electrophilic di-chloro platinum moiety that preferentially alkylated M40 and H44 residues. The compound, designated T2Pt, covalently cross-linked wild-type but not M40A/H44A PCNA, irreversibly inhibited PCNA/PIP-box interactions, and mildly alkylated plasmid DNA in vitro. In cells, T2Pt persistently induced cell cycle arrest, activated ATR-Chk1 signaling and modestly induced DNA strand breaks, features typical of cellular replication stress. Despite sustained activation of the replication stress response by the compound and its modestly genotoxic nature, T2Pt demonstrated little activity in clonogenic survival assays as a single agent, yet sensitized cells to cisplatin. The discovery of T2Pt represents an original effort directed at the development of irreversible PCNA inhibitors and sets the stage for the discovery of analogues more selective for PCNA over other cellular nucleophiles.

New heteronuclear gold(I)-platinum(II) complexes with cytotoxic properties: are two metals better than one?

A series of mono- and heterodinuclear gold(I) and platinum(II) complexes with a new bipyridylamine-phosphine ligand have been synthesized and characterized. The X-ray structures of the ligand precursor 4-iodo-N,N-di(pyridin-2-yl)benzamide, and of one gold derivative are reported. All the complexes display antiproliferative properties in vitro in human cancer cells in the range of cisplatin or higher, which appear to correlate with compounds' uptake. Interestingly, studies of the interactions of the compounds with models of DNA indicate different mechanisms of actions with respect to cisplatin. The biological activity study of these complexes provides useful information about the interest of designing multimetallic complexes for enhanced cytotoxic properties.

Synthesis, characterization and multi-spectroscopic DNA interaction studies of a new platinum complex containing the drug metformin

A new platinum(II) complex; [Pt(Met)(DMSO)Cl]Cl in which Met = metformin and DMSO: dimethylsulfoxide, was synthesized and characterized by (1)H NMR, IR, UV-Vis spectra, molar conductivity and computational methods. Binding interaction of this complex with calf thymus (CT) DNA has been investigated by using absorption, emission, circular dichroism, viscosity measurements, differential pulse voltammetry and cleavage studies by agarose gel electrophoresis. UV-Vis absorption studies showed hyperchromism. CD studies showed less perturbation on the base stacking and helicity bands in the CD spectrum of CT-DNA (B→C structural transition). In fluorimeteric studies, the Pt(II) complex can bind with DNA-NR complex and forms a new non-fluorescence adduct. The anodic peak current in the differential pulse voltammogram of the Pt(II) complex decreased gradually with the addition of DNA. Cleavage experiments showed that the Pt(II) complex does not induce any cleavage under the experimental setup. Finally all results indicated that Pt(II) complex interact with DNA via groove binding mode.

Beta-casein and its complexes with chitosan as nanovehicles for delivery of a platinum anticancer drug

The clinical application of platinum-based anticancer drugs is greatly limited by severe toxicity. Drug-delivery systems are much sought after to improve the efficacy and applicability of these drugs. Here, we describe a new drug-delivery system comprising a novel platinum complex (bipyridine morpholine dithiocarbamate Pt(II) nitrate) within nanoparticles composed of β-casein (β-CN) and chitosan (CS). The influence of pH on the formation of a colloidally-stable nanocarrier system composed of Pt complex-loaded β-CN and chitosan nanoparticles was investigated using UV-vis spectrometry, dynamic light scattering (DLS) and scanning electron microscopy (SEM). The particles of Pt complex-loaded beta-casein-chitosan formed were stable and soluble in the pH range 5.7-6.2. Hence, the optimal pH for complex formation is between the pI of casein (5.3) and the pKa of chitosan (6.5). DLS data showed that, at both pH values of 5.7 and 6.2, the particles formed had sizes between 200 and 300nm. However, the optimum pH for particle formation was pH 5.7. At this pH, the zeta-potential values of nanoparticles were positive and the particles were stable. SEM analysis confirmed the formation of nanoparticles with good colloidal stability and an average particle size of 200nm. The cytotoxicity of both free and encapsulated Pt complex was evaluated on colorectal carcinoma HCT116 cells. The results obtained indicated that both the cytotoxicity and cellular uptake of platinum were enhanced by its entrapment in β-CN-CS nanovehicles. These findings suggest that this novel drug-delivery system enables drugs to be thermodynamically stable in aqueous solutions and is potentially useful for targeted oral-delivery applications.