Palladium complexes: new candidates for anti-cancer drugs

A combined solid state, solution and DFT study of a dimethyl-cyclen-Pd(II) complex

A new palladium(II) complex containing the previously synthesized 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane ligand maltonis was prepared and characterized both in solution and in the solid state. Hirshfeld surface and energy framework analyses were also performed. Because maltonis already showed antineoplastic activity, the complexation of Pd(II), chosen as an alternative to Pt(II), was investigated to study its possible biological activity. UV-vis and NMR studies confirmed the formation and stability of the complex in aqueous solution at physiological pH. X-ray diffraction data revealed a structure where the Pd(II) ion is lodged in the dimethyl-cyclen cavity, with maltol rings facing each other (closed shape) even if they are not involved in the coordination. DFT analysis was performed in order to understand the most stable shape of the complex. In view of evaluating its possible bioactive conformation, the DFT study suggested a slight energetic preference for the closed one. The resulting closed complex was stabilized in the X-ray structure by intermolecular interactions that replace the intramolecular interactions present in the optimized complex. According to the DFT calculated formation energies, notwithstanding its rarity, the Pd(II) complex of maltonis is the thermodynamically preferred one among analogous complexes containing different metal ions (Pt(II), Co(II), and Cu(II)). Finally, to study its possible biological activity, the interaction between the Pd(II) complex of maltonis and nucleosides was evaluated through NMR and DFT calculations, revealing a possible interaction with purines via the maltol moieties.

Influence of acid-base equilibrium on interactions of some monofunctional coumarin Pd(II) complexes with biologically relevant nucleophiles-comprehensive kinetic study

This aimed to develop a comprehensive theoretical protocol for examining substitution reaction processes. The researchers used a theoretical quantum-mechanical protocol based on the QM-ORSA approach, which estimates the kinetic parameters of thermodynamically favourable reaction pathways. This theoretical protocol was validated by experimentally investigating substitution mechanisms in two previously synthesised Pd(II) complexes: chlorido-[(3-(1-(2-hydroxypropylamino)ethylidene)chroman-2,4-dione)]palladium(II) (C1) and chlorido-[(3-(1-(2-mercaptoethylamino)-ethylidene)-chroman-2,4dione)]palladium(II) (C2), along with biologically relevant nucleophiles, namely L-cysteine (l-Cys), L-methionine (l-Met), and guanosine-5'-monophosphate (5'-GMP). Reactions were investigated under pseudo-first-order conditions, monitoring nucleophile concentration and temperature changes using stopped-flow UV-vis spectrophotometry. All reactions were conducted under physiological conditions (pH = 7.2) at 37 °C. The reactivity of the studied nucleophiles follows the order: l-Cys > l-Met > 5'-GMP, and the reaction mechanism is associative based on the activation parameters. The experimental and theoretical data showed that C2 is more reactive than C1, confirming that the complexes' structural and electronic properties greatly affect their reactivity with selected nucleophiles. The study's findings have confirmed that the primary interaction occurs with the acid-base species L-Cys, mostly through the involvement of the partially negative sulfur atom (87.2%). On the other hand, C2 has a higher propensity for reacting with L-Cys-, primarily through the partially negative oxygen atom (92.6%). The implementation of this theoretical framework will significantly restrict the utilization of chemical substances, hence facilitating cost reduction and environmental protection.

Therapeutic and Diagnostic Agents based on Bioactive Endogenous and Exogenous Coordination Compounds

Metal-based coordination compounds have very special place in bioinorganic chemistry because of their different structural arrangements and significant application in medicine. Rapid progress in this field increasingly enables the targeted design and synthesis of metal-based pharmaceutical agents that fulfill valuable roles as diagnostic or therapeutic agents. Various coordination compounds have important biological functions, both those initially present in the body (endogenous) and those entering the organisms from the external environment (exogenous): vitamins, drugs, toxic substances, etc. In the therapeutic and diagnostic practice, both the essential for all living organisms and the trace metals are used in metal-containing coordination compounds. In the current review, the most important functional biologically active compounds were classified group by group according to the position of the elements in the periodic table.

Potent saccharinate-containing palladium(II) complexes for sensitization to cancer therapy

Palladium(II) (Pd^II) complexes are among the most promising anticancer compounds. Both 2`-benzoylpyridine thiosemicarbazone (BpT) and saccharinate (Sac) are efficient metal chelators with potent anticancer activity. To explore a more effective new anticancer drug, we synthesized a series of Sac and BpT-containing Pd^II complexes coordinated with thiosemicarbazone (TSC)-derived ligands, and characterized them through nuclear magnetic resonance (NMR), Fourier transformed infrared spectroscopy (FT-IR), elemental analysis, ultraviolet-visible spectroscopy (UV-Vis) and thermogravimetric analysis (TGA). Each target complex was composed of Pd^II, BpT, and one or two Sac molecules. Both the in vitro and in vivo anti-growth effects of those ligands and the obtained Pd^II complexes were investigated in the human lung adenocarcinoma cell lines A549 and Spc-A1. The coordination of Pd^II with the TSC-derivatives and Sac resulted in clearly greater anticancer activity than single ligands. These compounds were demonstrated to be safe for 293 T normal human kidney epithelial cells. The introduction of Sac into the TSC-derived Pd^II complex significantly enhanced anti-growth effects, and induced apoptosis of human lung cancer cells in vitro and in vivo in a dose dependent manner. Moreover, the Pd^II complex containing two Sac molecules showed the most promising therapeutic effects, thereby confirming that Sac increases the cancer therapeutic efficacy of Pd^II complexes and providing a new strategy for exploring anticancer drugs for potential clinical treatment.

Cytotoxicity Induced by Newly Synthesized Palladium (II) Complexes Lead to the Death of MCF-7 and MDA-MB-435 Cancer Cell Lines

Purpose: Breast cancer is the most common female malignancy and melanoma is the most lethal type of skin cancer. Traditional therapy for cancer treatment is far from satisfactory due to drug resistance and side effects, thus a search for new medicines is being emphasized. Palladium(II) complexes have been reported as anticancer potential agents. In this work, the anticancer activities and cell death induction of a new series of square-planar Pd(II) complexes were evaluated against MCF-7 and MDA-MB-435 cancer cells. Methods: MCF-7 (breast carcinoma) and MDA-MB-435 (melanoma) cells were cultivated, and treated with ligand and Pd(II) complexes. Cell growth, migration and adhesion inhibition, morphological alterations, cell death induction and, DNA interaction upon treatment were studied. Results: Pd(II) complexes exhibited both short and long-term antiproliferative effects on both cell lines, reducing by 80% cell growth in the SRB assay and abolishing longterm proliferation, estimated by the clonogenic assay. Complexes reduced significantly (P<0.05) cell migration and adhesion when compared to the control group. Complexes induced morphological alterations in cell lines and significant (P<0.05) cellular shrinkage. Cell death was induced and the complexes were able to interact with DNA, inducing cleavage of double-stranded DNA, which may account for the complexes cytotoxic effects, observed against both MCF-7 and MDA-MB-435 cells. Conclusion: Overall, the complexes exhibited cytotoxic activities and induced cell death. These observations emphasize an anticancer role with a potential therapeutic value for Pd(II) complexes to improve the outcome of patients with breast cancer and melanoma.

First evaluation of the anxiolytic-like effects of a bromazepam‑palladium complex in mice

A significant fraction of patients are affected by persistent fear and anxiety. Currently, there are several anxiolytic drug options, however their clinical outcomes do not fully manage the symptoms. Here, we evaluated the effects of a bromazepam‑palladium derivative [2-{(7-bromo-2-oxo-1,3-dihydro-2H-1,4-benzodiazepin-5-il)pyridinyl-κ²-N,N}chloropalladium(II)], [(BMZ)PdCl₂], on fear/anxiety and memory-related behavior in mice. For this, female Swiss mice were treated intraperitoneally (i.p.) with saline (NaCl 0.9%) or [(BMZ)PdCl₂] (0.5, 5.0, or 50 μg/kg). After 30 min, different tests were performed to evaluate anxiety, locomotion, and memory. We also evaluated the acute toxicity of [(BMZ)PdCl₂] using a cell viability assay (neutral red uptake assay), and whether the drugs mechanism of action involves the γ-aminobutyric acid type A (GABA_A) receptor complex by pre-treating animals with flumazenil (1.0 mg/kg, i.p., a competitive antagonist of GABA_A-binding site). Our results demonstrate that [(BMZ)PdCl₂] induces an anxiolytic-like phenotype in the elevated plus-maze test and that this effect can be blocked by flumazenil. Furthermore, there were no behavioral alterations induced by [(BMZ)PdCl₂], as evaluated in the light-dark box, open field, and step-down passive avoidance tests. In the acute toxicity assay, [(BMZ)PdCl₂] presented IC₅₀ and LD₅₀ values of 218 ± 60 μg/mL and 780 ± 80 mg/kg, respectively, and GSH category 4. Taken together, our results show that the anxiolytic-like effect of acute treatment with [(BMZ)PdCl₂] occurs through the modulation of the benzodiazepine site in the GABA_A receptor complex. Moreover, we show indications that [(BMZ)PdCl₂] does not promote sedation and amnesia and presents the same toxicity as the bromazepam prototype.

Cytotoxic effects of Pd(II) complexes on cancer and normal cells: Their DNA & BSA adduct formation and theoretical approaches

Herein, we report the synthesis and characterisation of a series of Pd(II) complexes: Pd(TEEDA)Cl₂, C-1; [Pd(TEEDA)(OH₂)₂](NO₃)₂, C-2; [Pd(TEEDA)(l-cys)](NO₃)₂, C-3; [Pd(TEEDA)(NALC)], C-4; [Pd(TEEDA)(Meth)](NO₃)₂, C-5; and [Pd(TEEDA)(GSH)], C-6 (where TEEDA = N,N,N'-Triethylenediamine, l-cys = l-cysteine, NALC = N-acetyl-l-cysteine, Meth = dl-methionine and GSH = glutathione). UV-Vis spectroscopic characterisation was supported by TD-DFT theoretical simulation using Gaussian09 software. Different reactivity parameters were calculated from the energy difference between HOMO and LUMO of the complexes by DFT. The bonding mode of the labile ligands was confirmed by NBO analysis. Interaction of the complexes with DNA has been observed by gel electrophoresis experiment. DNA binding nature as well as binding constants of the complexes were measured with UV-Vis and fluorescence spectroscopic method. The binding nature of the complexes with DNA was confirmed by viscometric titration. Interaction of the complexes with BSA was investigated by UV-Vis and fluorescence titration method. Cytotoxic activity of the Pd(II) complexes was evaluated on A549 (lung carcinoma epithelial cells), HCT116(Colorectal Carcinoma) and HEK293 (Human embryonic kidney cells) cell lines. The ROS generation in the presence of the complexes was tested both on cancer cell lines A549 and HCT116 as well as human normal cell HEK293.

Facing Diseases Caused by Trypanosomatid Parasites: Rational Design of Pd and Pt Complexes With Bioactive Ligands

Human African Trypanosomiasis (HAT), Chagas disease or American Trypanosomiasis (CD), and leishmaniases are protozoan infections produced by trypanosomatid parasites belonging to the kinetoplastid order and they constitute an urgent global health problem. In fact, there is an urgent need of more efficient and less toxic chemotherapy for these diseases. Medicinal inorganic chemistry currently offers an attractive option for the rational design of new drugs and, in particular, antiparasitic ones. In this sense, one of the main strategies for the design of metal-based antiparasitic compounds has been the coordination of an organic ligand with known or potential biological activity, to a metal centre or an organometallic core. Classical metal coordination complexes or organometallic compounds could be designed as multifunctional agents joining, in a single molecule, different chemical species that could affect different parasitic targets. This review is focused on the rational design of palladium(II) and platinum(II) compounds with bioactive ligands as prospective drugs against trypanosomatid parasites that has been conducted by our group during the last 20 years.

Smart poly(amidoamine) dendron-functionalized magnetic graphene oxide for cancer therapy

A novel multicomponent magnetic nanocomposite whose drug release behavior is pH and temperature dependent.

New Prospects in Nano Phased Co-substituted Hydroxyapatite Enrolled in Polymeric Nanofiber Mats for Bone Tissue Engineering Applications

The most common forms of tissue impairment are fracture bones and significant bone disorders caused by multiple traumas or normal aging. Surgical care sometimes necessitates the placement of a temporary or permanent prosthesis, which continues to be a challenge for orthopedic surgeons, including those with large bone defects. Electrospun scaffolds made from natural and synthetic nanofiber-based polymers are studied as natural extracellular matrix (ECM)-like scaffolds for tissue engineering. Besides, nanostructured materials have properties and functions depending on the scale of natural materials such as hydroxyapatite (HAP), ranging from 1 to 100 nm, which activity was proficient upon enrolled in nanofiber mats. The use of nanofibers in combination with nano-HAP has increased the scaffold's ability to replicate the construction of natural bone tissue that is the aim of the present text. In bone engineering, nanofiber substrates facilitate cell adhesion, proliferation, and differentiation, while HAP induces cells to secrete ECM for bone mineralization and development. This review aims to draw the reader's attention to the critical issues with synthetic and natural polymers containing HAP in bone tissue engineering; co-substituted hydroxyapatite has also been mentioned.

Platinum and Palladium Complexes as Promising Sources for Antitumor Treatments

There is a need for new, safer, and more effective agents to treat cancer. Cytostatics that have transition metals at their core have attracted renewed interest from scientists. Researchers are attempting to use chemotherapeutics, such as cisplatin, in combination therapy (i.e., in order to enhance their effectiveness). Moreover, studies are being carried out to modify molecules, by developing them into multinuclear structures, linking different compounds to commonly used drugs, or encapsulating them in nanoparticles to improve pharmacokinetic parameters, and increase the selectivity of these drugs. Therefore, we attempted to organize recent drug findings that contain palladium and platinum atoms in their structures.

Insights into Multifunctional Nanoparticle-Based Drug Delivery Systems for Glioblastoma Treatment

Glioblastoma (GB) is an aggressive cancer with high microvascular proliferation, resulting in accelerated invasion and diffused infiltration into the surrounding brain tissues with very low survival rates. Treatment options are often multimodal, such as surgical resection with concurrent radiotherapy and chemotherapy. The development of resistance of tumor cells to radiation in the areas of hypoxia decreases the efficiency of such treatments. Additionally, the difficulty of ensuring drugs effectively cross the natural blood-brain barrier (BBB) substantially reduces treatment efficiency. These conditions concomitantly limit the efficacy of standard chemotherapeutic agents available for GB. Indeed, there is an urgent need of a multifunctional drug vehicle system that has potential to transport anticancer drugs efficiently to the target and can successfully cross the BBB. In this review, we summarize some nanoparticle (NP)-based therapeutics attached to GB cells with antigens and membrane receptors for site-directed drug targeting. Such multicore drug delivery systems are potentially biodegradable, site-directed, nontoxic to normal cells and offer long-lasting therapeutic effects against brain cancer. These models could have better therapeutic potential for GB as well as efficient drug delivery reaching the tumor milieu. The goal of this article is to provide key considerations and a better understanding of the development of nanotherapeutics with good targetability and better tolerability in the fight against GB.

Preclinical Pharmacokinetics and Biodistribution of Anticancer Dinuclear Palladium(II)-Spermine Complex (Pd2Spm) in Mice

Palladium-based compounds are regarded as potential analogs to platinum anticancer drugs with improved properties. The present study assessed the pharmacokinetics and biodistribution of a dinuclear palladium(II)-spermine chelate (Pd₂Spm), which has previously been shown to possess promising in vitro activity against several therapy-resistant cancers. Using inductively coupled plasma-mass spectrometry, the kinetic profiles of palladium/platinum in serum, serum ultrafiltrate and tissues (kidney, liver, brain, heart, lungs, ovaries, adipose tissue and mammary glands) were studied in healthy female Balb/c mice after a single intraperitoneal bolus injection of Pd₂Spm (3 mg/kg bw) or cisplatin (3.5 mg/kg bw) between 0.5 and 48 h post-injection. Palladium in serum exhibited biphasic kinetics with a terminal half-life of 20.7 h, while the free palladium in serum ultrafiltrate showed a higher terminal half-life than platinum (35.5 versus 31.5 h). Palladium was distributed throughout most of the tissues except for the brain, with the highest values in the kidney, followed by the liver, lungs, ovaries, adipose tissue and mammary glands. The in vitro cellular accumulation was also evaluated in breast cancer cells, evidencing a passive diffusion as a mechanism of Pd₂Spm’s cellular entry. This study reports, for the first time, the favorable pharmacokinetics and biodistribution of Pd₂Spm, which may become a promising pharmacological agent for cancer treatment.

Synthesis, characterization and antibacterial applications of pyrazolyl-sulfonamides and their palladium complexes

Pyrazolylsulphonamides compounds and their palladium complexes exhibiting good potential anti-bacterial activities.

Photoactive PtII and PdII complexes of N,N-diethyl-N′-3,4,5-trimethoxybenzoylthiourea: synthesis, crystal structures, DFT and cytotoxicity studies

New trans-Pd^II/Pt^II acylthiourea complexes prepared by photo-induced isomerism are found to be more cytotoxic than cis-Pd^II/Pt^II against human prostate cancer and normal embryonic kidney cell lines.

Gold(III) Complexes: An Overview on Their Kinetics, Interactions With DNA/BSA, Cytotoxic Activity, and Computational Calculations

In the last few years, metallodrugs play a key role in the development of medicinal chemistry. The choice of metal ion, its oxidation state and stability, and the choice of inert and labile ligands are just some of the very important facts which must be considered before starting the synthesis of complexes with utilization in medicinal purpose. As a result, a lot of compounds of different transition metal ions found application for diagnostic and therapeutic purpose. Beside all, gold compounds have attracted particular attention. It is well-known that gold compounds could be used for the treatment of cancer, HIV, rheumatoid arthritis (chrysotherapy), and other diseases. This metal ion has unoccupied d-sublevels and possibility to form compounds with different oxidation states, from -1 to +5. However, gold(I) and gold(III) complexes are dominant in chemistry and medicine. Especially, gold(III) complexes are of great interest due to their structural similarity with cisplatin. Accordingly, this review summarizes the chemistry of some mononuclear and polynuclear gold(III) complexes. Special attention is given to gold(III) complexes with nitrogen-donor inert ligands (aliphatic or aromatic that have a possibility to stabilize complex) and their kinetic behavior toward different biologically relevant nucleophiles, mechanism of interaction with DNA/bovine serum albumin (BSA), cytotoxic activity, as well as computational calculations.

PLGA-nanoparticles loaded with a thiosemicarbazone derived palladium(ii) complex as a potential agent to new formulations for human ovarian carcinoma treatment

The encapsulation process of the Pd^II complex [PdCl(PPh₃)(PrCh)], a promising cytotoxic agent on ovarian cancer cells, in PLGA polymer was studied. The cytotoxicity results showed that the formulation led to a significant reduction of the ovarian cell viability (80% at 1 μM).

The palladacycle complex AJ-5 induces apoptotic cell death while reducing autophagic flux in rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) forms in skeletal muscle and is the most common soft tissue sarcoma in children and adolescents. Current treatment is associated with debilitating side effects and treatment outcomes for patients with metastatic disease are dismal. Recently, a novel binuclear palladacycle, AJ-5, was shown to exert potent cytotoxicity in melanoma and breast cancer and to present with negligible adverse effects in mice. This study investigates the anti-cancer activity of AJ-5 in alveolar and embryonal RMS. IC50 values of ≤ 0.2 µM were determined for AJ-5 and it displayed a favourable selectivity index of >2. Clonogenic and migration assays showed that AJ-5 inhibited the ability of RMS cells to survive and migrate, respectively. Western blotting revealed that AJ-5 induced levels of key DNA damage response proteins (γH2AX, p-ATM and p-Chk2) and the p38/MAPK stress pathway. This correlated with an upregulation of p21 and a G1 cell cycle arrest. Annexin V-FITC/propidium iodide staining revealed that AJ-5 induced apoptosis and necrosis. Apoptosis was confirmed by the detection of cleaved PARP and increased levels and activity of cleaved caspases-3, -7, -8 and -9. Furthermore, AJ-5 reduced autophagic flux as shown by reduced LC3II accumulation in the presence of bafilomycin A1 and a significant reduction in autophagosome flux J. Finally, pharmacokinetic studies in mice show that AJ-5 has a promising half-life and that its volume of distribution is high, its clearance low and its intraperitoneal absorption is good. Together these findings suggest that AJ-5 may be an effective chemotherapeutic with a desirable mechanism of action for treating drug-resistant and advanced sarcomas.

Crystal structures, spectroscopic properties of new cobalt(II), nickel(II), zinc(II) and palladium(II) complexes derived from 2-acetyl-5-chloro thiophene thiosemicarbazone: Anticancer evaluation

The reactions of cobalt(II), nickel(II), zinc(II) chlorides and [Pd(DMSO)₂Cl₂] with 2-acetyl-5-chloro-thiophene thiosemicarbazone (HL) leads to the formation of a series of new complexes: [CoCl₂(S-HL)₂], 1; [Ni(N,S-L)₂], 2 [ZnCl₂(S-HL)₂], 3 and [PdCl₂(N,S-HL)], 4. All the complexes have been characterized by elemental analysis, IR, LC-MS. ¹H and ¹³C NMR spectroscopy have been performed for Zn(II) and Pd(II) complexes. The crystal structures of the complexes 1-3 have been determined by single-crystal X-ray diffraction methods. The compounds, (1) and (3), crystallized in the monoclinic crystal system with C2/c space group. In both complexes, the metal centers are four-coordinated in a distorted tetrahedral configuration by two sulfur atoms from two thiosemicarbazone ligands and two Cl anions. The crystal structure of (2) consists of monomeric entities where the nickel(II) ion exhibit distorted square planar geometry. The coordination geometry around nickel ion is four-coordinate with four atoms of the two chelating thiosemicarbazone ligands which are in cis position. The τ₄ value of 0.255 obtained from the τ₄ analysis of complex (2) shows that the four-coordinate geometry around the central nickel ion is close to square planar. Complex (4) is mononuclear, the central ion is coordinated through the sulfur and the azomethine nitrogen atom of neutral ligand. The cytotoxic effects of all complexes were analyzed for three cancer cell lines, Caco-2, DLD-1, and SW620 compared to normal colon epithelial cell line, CCD18Co. Complex (4) is more active against DLD-1, SW620 and Caco-2 than CCD18Co. The efficiency of complex (4) is more effective in aggressive cancer cell lines. Therefore, it can be used as a new chemotherapeutic, especially in the treatment of resistant cancer types caused by long-term use of platinum-based drugs.

Phenoxide chelated Ir(iii) N-heterocyclic carbene complexes: synthesis, characterization, and evaluation of their in vitro anticancer activity

Twelve novel half-sandwich IrIII-NHC complexes [(η5-Cpx)Ir(C^O)Cl] were synthesized and characterized. These complexes showed higher cytotoxic activity toward A549 cells and HeLa cells than cisplatin. An increase in the number of contained phenyl groups was related to better anticancer activity. The reaction of complexes with nucleobases 9-MeA, nucleobases 9-EtG, plasmid DNA and CT-DNA showed no significant effects. These complexes captured hydrogen from NADH and converted it to NAD+, which produced the reactive oxygen species (ROS). ROS led to a decrease in the mitochondrial membrane potential and lysosomal damage, finally inducing apoptosis.

Biological evaluations of newly-designed Pt(II) and Pd(II) complexes using spectroscopic and molecular docking approaches

To perform biological evaluations of newly-designed Pt(II) and Pd(II) complexes, the present study was conducted with targeted protein human serum albumin (HSA) and HCT116 cell line as model of human colorectal carcinoma. The binding of Pt(II) and Pd(II) complexes to HSA was analyzed using fluorescence spectroscopy and molecular docking. The thermal stability and alterations in the secondary structure of HSA in the presence of Pt(II) and Pd(II) complexes were investigated using the thermal denaturation method and circular dichroism (CD) spectroscopy. The cytotoxicity of the Pt(II) and Pd(II) complexes was studied against the HCT116 cell line using MTT assay. The binding analysis revealed that the fluorescence findings were well in agreement with docking results such that there is only one binding site for each complex on HSA. Binding constants of 8.7 × 10³ M^-1, 2.65 × 10³ M^-1, 0.3 × 10³ M^-1, and 4.4 × 10³ M^-1 were determined for Pd(II) and Pt(II) complexes (I-IV) at temperature of 25 °C, respectively. Also, binding constants of 1.9 × 10³ M^-1, 15.17 × 10³ M^-1, 1.9 × 10³ M^-1, and 13.1 × 10³ M^-1 were determined for Pd(II) and Pt(II) complexes (I-IV) at temperature of 37 °C, respectively. The results of CD and thermal denaturation showed that the molecular structure of HSA affected by interaction with Pt(II) and Pd(II) complexes is stable. Cytotoxicity studies represented the growth suppression effect of the Pt(II) and Pd(II) complexes toward the human colorectal carcinoma cell line. Therefore, the results suggest that the new designed Pt(II) and Pd(II) complexes are well promising candidates for use in cancer treatment, particularly for human colorectal cancer. Communicated by Ramaswamy H. Sarma.

2,2'- bipyridine coplanar with coordination square of Pd(II) nonyldithiocarbamato antitumor complex interacting with DNA in two distinct steps

Cisplatin is one of the most effective chemotherapy drugs, and has been widely employed for more than four decades in the treatment of different forms of human tumors. In recent years, various examples of metal complex-based compounds have been used for medicinal purposes. In this context, the novel palladium(II) complex, [Pd(non-dtc)(bpy)]NO₃, (non-dtc = nonyldithiocarbamate and bpy = 2,2'- bipyridine) has been synthesized and characterized by means of elemental analysis, conductivity measurements, FT-IR, ¹H NMR, ¹³C NMR, and electronic spectroscopy studies. The 50% cytotoxic concentrations (Ic₅₀) of this Pd(II) complex (0.53 mM) and cisplatin (154 mM) against human cell tumor line (K562) indicates its interaction with DNA of cancer cell at quite low concentration. Thus, binding characteristics of this compound to calf thymus DNA (CT-DNA) has been investigated by UV-vis absorption spectroscopy and fluorescence spectra. The exciting observation of this work in the UV-visible studies was that the Pd(II) complex exhibit two or more types of interaction with CT-DNA. Such properties have rarely been observed in the literature. This complex cooperatively binds with DNA and denatures it too. Fluorescence studies proved the intercalation mode of binding and the other modes seems to be hydrophobic and electrostatic interactions. Binding parameters and thermodynamics of the interaction with CT-DNA are also described. Finally, multifunctional interactions of [Pd(non-dtc)(bpy)]NO₃ make it suitable to interact with DNA of cancer cell at quite low concentration and if it is used as anticancer agent, very low doses will be needed which may have fewer side effects.