Platinum and ruthenium complexes of new long-tail derivatives of PTA (1,3,5-triaza-7-phosphaadamantane): Synthesis, characterization and antiproliferative activity on human tumoral cell lines

Gold(I) Complexes Bearing Alkylated 1,3,5-Triaza-7-phosphaadamantane Ligands as Thermoresponsive Anticancer Agents in Human Colon Cells

Overheating can affect solubility or lipophilicity, among other properties, of some anticancer drugs. These temperature-dependent changes can improve efficiency and selectivity of the drugs, since they may affect their bioavailability, diffusion through cell membrane or activity. One recent approach to create thermosensitive molecules is the incorporation of fluorine atoms in the chemical structure, since fluor can tune some chemical properties such as binding affinity. Herein we report the anticancer effect of gold derivatives with phosphanes derived from 1,3,5-triaza-7-phosphaadamantane (PTA) with long hydrocarbon chains and the homologous fluorinated chains. Besides, we analysed the influence of temperature in the cytotoxic effect. The studied gold(I) complexes with phosphanes derived from PTA showed antiproliferative effect on human colon carcinoma cells (Caco-2/TC7 cell line), probably by inhibiting cellular TrxR causing a dysfunction in the intracellular redox state. In addition, the cell cycle was altered by the activation of p53, and the complexes produce apoptosis through mitochondrial depolarization and the consequent activation of caspase-3. Furthermore, the results suggest that this cytotoxic effect is enhanced by hyperthermia and the presence of polyfluorinated chains.

New organometallic ruthenium(ii) complexes with purine analogs - a wide perspective on their biological application

Three half-sandwich organometallic ruthenium(ii) complexes containing purine analogs such as triazolopyrimidines of general formula [(η6-p-cym)Ru(L)Cl2], where p-cym represents p-cymene and L is 5,6,7-trimethyl-1,2,4-triazolo[1,5-a]pyrimidine (tmtp for 1), 5,7-diethyl-1,2,4-triazolo[1,5-a]pyrimidine (detp for 2) and 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO for 3), have been synthesized and characterized by elemental analysis, infrared, multinuclear magnetic resonance spectroscopic techniques (1H, 13C, 15N), and single-crystal X-ray diffraction (for 1 and 2). All these complexes have been thoroughly screened for their in vitro cytotoxicity against MCF-7 and HeLa cell lines as well as L929 murine fibroblast cells, indicating [(η6-p-cym)Ru(HmtpO)Cl2] (3) as the most active representative against the HeLa cell line and simultaneously being 64-fold less toxic to normal L929 murine fibroblast cells than cisplatin. At the same time, 3 has shown antimetastatic activity comparable to NAMI-A against HeLa cells both after 24 and 48 h of treatment in a wound healing assay. In order to better understand the mechanism of anticancer action and differences in the cytotoxic activity of 1-3, the studies were expanded to determining their lipophilicity, the kinetic stability at pH 6.5-8, the effect on reactive oxygen species (ROS) production in HeLa cells and interactions with significant biomolecules (DNA and albumin) by using molecular docking and circular dichroism (CD) experiments. Furthermore, antiparasitic studies against L. braziliensis, L. infantum and T. cruzi reveal that the newly synthesized complexes 1-3 are very promising candidates which can compete with commercial antiparasitic drugs. Complex 3 in particular, on top of exhibiting a high antiparasitic effect (IC50 < 1 μM against two strains), reaches a selectivity index >1000.

Pentafluorophenyl Platinum(II) Complexes of PTA and its N-Allyl and N-Benzyl Derivatives: Synthesis, Characterization and Biological Activity

From the well-known 1,3,5-triaza-phosphaadamantane (PTA, 1a), the novel N-allyl and N-benzyl tetrafuoroborate salts 1-allyl-1-azonia-3,5-diaza-7-phosphaadamantane (APTA(BF₄), 1b) and 1-benzyl-1-azonia-3,5-diaza-7-phosphaadamantane (BzPTA(BF₄), 1c) were obtained. These phosphines were then allowed to react with (Pt(μ-Cl)(C₆F₅)(tht))₂ (tht = tetrahydrothiophene) affording the water soluble Pt(II) complexes trans-(PtCl(C₆F₅)(PTA)₂) (2a) and its bis-cationic congeners trans-(PtCl(C₆F₅)(APTA)₂)(BF₄)₂ (2b) and trans-(PtCl(C₆F₅)(BzPTA)₂)(BF₄)₂ (2c). The compounds were fully characterized by multinuclear NMR, ESI-MS, elemental analysis and (for 2a) also by single crystal X-ray diffraction, which proved the trans configuration of the phosphine ligands. Furthermore, in order to evaluate the cytotoxic activities of all complexes the normal human dermal fibroblast (NHDF) cell culture were used. The antineoplastic activity of the investigated compounds was checked against the human lung carcinoma (A549), epithelioid cervix carcinoma (HeLa) and breast adenocarcinoma (MCF-7) cell cultures. Interactions between the complexes and human serum albumin (HSA) using fluorescence spectroscopy and circular dichroism spectroscopy (CD) were also investigated.

A new amido-phosphine of dichloroacetic acid as an active ligand for metals of pharmaceutical interest. Synthesis, characterization and tests of antiproliferative and pro-apoptotic activity

We herein describe the synthesis and characterization of the new amido-phosphinic ligand 3,7‑bis(dichloroacetyl)‑1,3,7‑triaza‑5‑phosphabicyclo[3.3.1]nonane (DCP), a derivative of dichloroacetic acid (DCA), whose ability to reverse the suppressed mitochondrial apoptosis in cancer cells is known. DCP was obtained by a double N-acylation of PTA (1,3,5‑triaza‑7‑phosphaadamantane) occurring with loss of CH₂, in appropriate conditions_. Due to the hindered rotation around the amidic CN bonds, three rotameric forms of DCP were observed, whose ratio in solution was dependent on the solvent, while the X-ray crystal structure of DCP showed an opposite orientation of the two amidic carbonyl groups (anti rotamer). The lipophilic, air and thermally stable DCP was found able to act regiospecifically as a P-donor ligand toward soft metal ions. By ligand substitution on appropriate precursors, we obtained the complexes 1-9, where proapoptotic DCA is associated with metal ions of known cytotoxic activity on cancer cells (Pt²⁺, Pd²⁺, Ru²⁺, Re⁺, Au⁺). The antiproliferative activity of DCP and its complexes was tested in vitro, in comparison with cisplatin, on three human tumor cell lines: A2780 (ovarian cisplatin-sensitive), A2780cis (ovarian cisplatin-resistant) and K562 (erythroleukemic). The results showed that the simultaneous presence of DCP (containing two residues of proapoptotic DCA) and Pt(II) produces the best performances with respect to non-platinum complexes. Experiments of pro-apoptotic activity indicated that the antiproliferative activity of the most active DCP-Pt(II) complexes is associated with induction of apoptosis.

Water soluble derivatives of platinum carbonyl Chini clusters: synthesis, molecular structures and cytotoxicity of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2-

The reactions of [Pt3n(CO)6n]2- (n = 2-5) homoleptic Chini-type clusters with increasing amounts of 1,3,5-triaza-7-phosphaadamantane (PTA) result in the stepwise substitution of one terminal CO ligand per Pt3 triangular unit up to the formation of [Pt3n(CO)5n(PTA)n]2- (n = 2-5). Competition between the nonredox substitution with retention of the nuclearity and the redox fragmentation to afford lower nuclearity heteroleptic Chini-type clusters is observed as a function of the amount of PTA and the nuclearity of the starting cluster. Because of this, [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- are more conveniently obtained via the oxidation of [Pt9(CO)15(PTA)3]2-. All the new species were spectroscopically characterized, and the structures of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- were determined by single-crystal X-ray diffraction. These clusters may be viewed as heteroleptic Chini-type clusters composed of stacks of four and five Pt3(μ-CO)3(CO)2(PTA) units, respectively. The solubility in water of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- has been determined and their cytotoxicity towards human ovarian (A2780) cancer cells and their cisplatin-resistant strain (A2780cisR) has been evaluated.

Solid lipid nanoparticles for the delivery of 1,3,5-triaza-7-phosphaadamantane (PTA) platinum (II) carboxylates

The use of solid lipid nanoparticles (SLN) is a promising route for the delivery of platinum complexes aimed to anticancer activity. This paper describes the production and characterization of SLN suitable for the loading of Pt complexes containing the biocompatible phosphine 1,3,5-triaza-7-phosphaadamantane (PTA) as neutral ligand. After a screening of several lipidic phases, stearic acid-based SLN were identified as the most appropriate for the purpose. They were produced by emulsion-dilution method and then characterized in terms of dimension, polydispersity, time stability, pH balance and morphological aspect. Stearic acid SLN are designed as a system able to coordinate to platinum, acting as anionic carboxylic ligands, replacing the base carbonate of the Pt synthon [PtCO₃(DMSO)₂], where also DMSO can subsequently be substituted by phosphinic ligands, namely PTA. SLN functionalised with Pt-PTA were produced and characterized by this synthetic route. The toxicity of plain SLN and the antiproliferative effect of SLN functionalised with Pt-PTA were evaluated on two human cancer cell lines K562 and A2780. The results indicate that SLN can be exploited as a delivery system for Pt complexes with potential anticancer activity.

Nafion®-Containing Solid Lipid Nanoparticles as a Tool for Anticancer Pt Delivery: Preliminary Studies

Preliminary studies of nanoparticles based on the perfluorosulfonic acid resin Nafion have been carried out with the aim of establishing an ionic connection with the protonable phosphine 1,3,5-triaza-7-phosphaadamantane (PTA), suitable for the coordination of platinum. Nafion-containing nanoparticles (NAF) were produced by homogenization followed by ultrasonication method. After production, NAF were characterized in terms of size, morphology, andin vitrocytotoxicity. The PCS studies showed that theZ-average mean diameter was around 250 nm. Moreover, the polydispersity index showed a monodimensional distribution of nanoparticles. Cryo-TEM analysis showed a uniform and homogenous population of particles, characterized by the presence of both ovoidal and needle-like structures. To evaluate thein vitrocytotoxicity, NAF were tested on human cancer cell lines K562 and A2780. No cytotoxic effect was found on both cell lines. By13P-NMR measures, it is here proved that the strongly acidic sulfonic groups of Nafion-containing nanoparticles (NAF) can act as protonating agents for PTA. The protonation occurs selectively at nitrogen; hence protonated PTA maintains its ability to coordinate platinum via its phosphorus atom.

The anticancer effect related to disturbances in redox balance on Caco-2 cells caused by an alkynyl gold(I) complex

The alkynyl gold(I) derivative [Au(C≡CPh)(PTA)] (PTA=1,3,5-triaza-7-phosphaadamantane) induces apoptosis in colorectal carcinoma tumour cells (Caco-2) without affecting to normal enterocytes. [Au(C≡CPh)(PTA)] is a slight lipophilic drug, stable in PBS (Phosphate Buffered Saline) and able to bind BSA (Bovin Serum Albumin) by hydrophobic interactions. Once inside the cell, [Au(C≡CPh)(PTA)] targets seleno proteins such as Thioredoxin Reductase 1, increasing ROS (Reactive Oxygen Species) levels, reducing cell viability and proliferation and inducing mitochondrial apoptotic pathway, pro-apoptotic and anti-apoptotic protein imbalance, loss of mitochondrial membrane potential, cytochrome c release and activation of caspases 9 and 3. Moreover, unlike other metal-based drugs such as cisplatin, [Au(C≡CPh)(PTA)] does not target nucleic acid, reducing the risk of side mutation in the DNA. In consequence, our results predict a promising future for [Au(C≡CPh)(PTA)] as a chemotherapeutic agent for colorectal carcinoma.

Lipid-based nanoparticles containing cationic derivatives of PTA (1,3,5-triaza-7-phosphaadamantane) as innovative vehicle for Pt complexes: Production, characterization and in vitro studies

The aliphatic phosphine PTA (1,3,5-triaza-7-phosphaadamantane) is a promising ligand for metal complexes designed and developed as innovative inorganic drugs. In the present paper, an N-alkylated derivative of PTA, (PTAC16H33)X (X=I, C1, or X=PF6, C2) and its platinum coordination complex cis-[PtCl2(PTAC16H33)2](PF6)2, C3, were considered as components of cationic lipid nanoparticles (CLNs). Particularly, CLN1, CLN2 and CLN3 were obtained by adding derivatives C1, C2 or C3 during nanoparticles preparation, while CLN2-Pt were obtained by treating preformed CLN2 with Pt(II). It was demonstrated that CLN1, CLN2 and CLN3 can be produced with technological conventional methods. However, among the two here proposed protocols, the one based on the treatment of preformed nanoparticles appears more advantageous as compared to the other since it allows a quantitative association yield of Pt. As determined by ICP-OES, a content of P and Pt 2.2-fold and 2.5-fold higher in CLN2-Pt than in CLN3 was evidenced. For the first time was demonstrated that properly functionalized preformed nanoparticles can be efficiently used to obtain a post production Pt(II) complex while maintaining a cytotoxic activity toward cultured cells. In fact, the antiproliferative activity shown by CLN3, CLN2-Pt on the three model cancer cell lines was substantially similar and comparable to that of complex C3 in dmso solution. Thus N-alkylated-PTA derivatives in CLNs could be proposed as innovative biocompatible and water dispersible nanoparticles carrying lipophilic Pt complexes becoming an interesting and improved system with respect to dmso solution.

Modulating the Anticancer Activity of Ruthenium(II)-Arene Complexes

Following the identification of [Ru(η(6)-p-cymene)Cl2(1H,1H,2H,2H-perfluorodecyl-3-(pyridin-3-yl)propanoate)], a ruthenium(II)-arene complex with a perfluoroalkyl-modified ligand that displays remarkable in vitro cancer cell selectivity, a series of structurally related compounds were designed. In the new derivatives, the p-cymene ring and/or the chloride ligands are substituted by other ligands to modulate the steric bulk or aquation kinetics. The new compounds were evaluated in both in vitro (cytotoxicity and migration assays) and in vivo (chicken chorioallantoic membrane) models and were found to exhibit potent antivascular effects.