Spectroscopic and cytotoxic studies of the novel designed palladium(II) complexes: β-Lactoglobulin and K562 as the targets

Spectroscopic and theoretical investigation of oxali-palladium interactions with β-lactoglobulin

The possibility of using a small cheap dairy protein, β-lactoglobulin (β-LG), as a carrier for oxali-palladium for drug delivery was studied. Their binding in an aqueous solution at two temperatures of 25 and 37°C was investigated using spectroscopic techniques in combination with a molecular docking study. Fluorescence intensity changes showed combined static and dynamic quenching during β-LG oxali-palladium binding, with the static mode being predominant in the quenching mechanism. The binding and thermodynamic parameters were determined by analyzing the results of quenching and those of the van't Hoff equation. According to obtained results the binding constants at two temperatures of 25 and 37°C are 3.3×10(9) M(-1) and 18.4×10(6) M(-1) respectively. Fluorescence resonance energy transfer (FRET) showed that the experimental results and the molecular docking results were coherent. An absence change of β-LG secondary structure was confirmed by the CD results. Molecular docking results agreed fully with the experimental results since the fluorescence studies also revealed the presence of two binding sites with a negative value for the Gibbs free energy of binding of oxali-palladium to β-LG. Furthermore, molecular docking and experimental results suggest that the hydrophobic effect plays a critical role in the formation of the oxali-palladium complex with β-LG. This agreement between molecular docking and experimental results implies that docking studies may be a suitable method for predicting and confirming experimental results, as shown in this study. Hence, the combination of molecular docking and spectroscopy methods is an effective innovative approach for binding studies, particularly for pharmacophores.

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.

Promising anti-growth effects of palladium(II) saccharinate complex of terpyridine by inducing apoptosis on transformed fibroblasts in vitro

Fibrosarcoma is one of the fatal cancer types and there is still not satisfactory success in its treatment despite new drugs. Therefore, the search for a new compound has been going on. It is currently known that some palladium-based anti-cancer compounds seem to have powerful apoptosis-inducing effects in cancer cells. For this purpose, a palladium(II)-saccharinate complex containing terpyridine which was synthesized by our research group was investigated in terms of its anti-tumor effects against mouse embryonic fibroblast NIH/3T3 (normal cell line) and rat embryonic fibroblast 5RP7 (H-ras transformed cell line) in vitro. The MTT and ATP viability assays were used to determine anti-growth/cytotoxic effects. Cytotoxic activity was confirmed by real time cytotoxicity analysis system. Flow cytometry analysis was further used to determine the mode of cell death (apoptosis/necrosis). Apoptosis was confirmed by triple-staining the cells with Hoechst 33342/PI/Calcein-AM triple and evaluated with fluorescence microscopy. It was found that the compound showed significant anti-growth activity by inducing apoptosis in a dose dependent manner. In conclusion, taking into account the cytotoxic activity of the compound at even relatively lower doses, in vivo experiments to elucidate its potential use for the treatment of fibrosarcoma are warranted.

Self-assembled metalla-rectangles bearing azodipyridyl ligands: synthesis, characterization and antitumor activity

Sixteen arene-Ru based molecular-rectangles were self-assembled in high yields by the equimolar mixing of arene-Ru acceptors (Aa-Ad) with various azopyridyl ligands (1,2-di(pyridyl-4yl)diazene (L1), 1,2-bis(pyridin-4-ylmethylene)hydrazine (L2), 1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine (L3), 1,2-bis(pyridin-4-ylmethylene)hydrazine (L4)) in nitromethane-methanol solutions. These new molecular-rectangles were fully characterized by a host of analytical techniques including elemental analysis, (1)H and (13)C NMR and HR-ESI-MS. The solid-state structures of two molecular-rectangles (1b and 4d) were determined by single crystal X-ray diffraction data. UV-visible and fluorescence studies were also carried out for the entire suite of rectangles. As with recent studies of similar arene-Ru complexes, the anti-proliferative activities of these complexes were evaluated against SK-hep-1 (liver cancer) and A-549 (lung cancer) human cancer lines. Additionally, the cellular pharmacology and intracellular localizations in AGS (gastric cancer) human cancer cells were determined for selected complexes (1c, 1d and 4c) by apoptosis and fluorescence microscopy studies. These studies confirm that arene-Ru molecular-rectangles inhibit cell cycle progression to the G0 phase, in contrast to that of cisplatin which arrests cell growth in the G2 phase.

DNA-binding, spectroscopic and antimicrobial studies of palladium(II) complexes containing 2,2'-bipyridine and 1-phenylpiperazine

With the purpose of evaluating the ability of Pd(II) complex to interact with DNA molecule as the main biological target, two new complexes [Pd(bpy)(OH(2))(2)] (1) and [Pd(Phenpip)(OH(2))(2)] (2), where (bpy=2,2'-bipyridine; Phenpip=1-phenylpiperazine), have been synthesized and the binding properties of these complexes with CT-DNA were investigated. The intrinsic binding constants (K(b)) calculated from UV-Vis absorption studies were 3.78×10(3) M(-1) and 4.14×10(3)M(-1) for complexes 1 and 2 respectively. Thermal denaturation has been systematically studied by spectrophotometric method and the calculated ΔT(m) was nearly 5 °C for each complex. All the results suggest an electrostatic and/or groove binding mode for the interaction between the complexes and CT-DNA. The redox behavior of the two complexes in the absence and in the presence of calf thymus DNA has been investigated by cyclic voltammetry. The cyclic voltammogram exhibits one quasi-reversible redox wave. The change in E(1/2), ΔE(p) and I(pc)/I(pa) supports that the two complexes exhibit strong binding to calf thymus DNA. Further insight into the binding of complexes with CT-DNA has been made by gel electrophoresis, where the binding of complexes is confirmed through decreasing the intensity of DNA bands. The two complexes have been screened for their antimicrobial activities using the disc diffusion method against some selected Gram-positive and Gram-negative bacteria. The activity data showed that both complexes were more active against Gram-negative than Gram-positive bacteria. It may be concluded that the antimicrobial activity of the compounds is related to cell wall structure of bacteria.

Biological evaluation and interaction of a newly designed anti-cancer Pd(II) complex and human serum albumin

The pharmacokinetics and pharmacodynamics of any drug will depend, largely, on the interaction that has with human serum albumin (HSA), the most abundant plasma protein. The interaction between newly synthesized Pd(II) complexe, 2,2'-bipyridin Butylglycinato Pd(II) nitrate, an anti-tumor component, with HSA was studied at different temperatures by fluorescence, far UV circular dichroism (CD), UV-visible spectrophotometry and theoretical approaches. The Pd(II) complex has a strong ability to quench the intrinsic fluorescence of HSA through a dynamic quenching procedure. The binding parameters and thermodynamic parameters, including δH°, δS° and δG° were calculated by fluorescence quenching method, indicated that hydrophobic forces play a major role in the interaction of Pd(II) complex with HSA. Based on Autodock, FRET (fluorescence resonance energy transfer) and fluorescence quenching data, it may be concluded that one of the binding sites in the complex of HSA is near the only one Trp of HSA (Trp214) in sub domain IIA of the protein. Far-UV-CD results indicated that Pd(II)-complex induced increase in the α-helical content of the protein. The anti-tumor property of the synthesized Pd(II) complex was studied by testing it on human tumor cell line K562. The 50% cytotoxic concentration (Cc₅₀) of complex was determined using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Also, fluorescence staining with DAPI (4,6-diamidino-2-phenylindole) revealed some typical nuclear changes that are characteristic of apoptosis which is induced at Cc₅₀ concentration of Pd(II) complex in K562 cell line after 24 h incubation. Our results suggest that Pd(II) complex is a promising anti-proliferative agent and should execute its biological effects by inducing apoptosis.

Binding studies of a novel antitumor palladium(II) complex to calf thymus DNA

The interaction of new 1, 10-phenanthrolineoctyldithiocarbamatopalladium (II) nitrate with DNA from calf thymus was investigated at 300 and 310 K in a Tris-HCl buffer of pH 7.0 medium containing 20 mM sodium chloride. This water soluble, square planar Pd(II) complex has been synthesized and spectroscopic (electronic, infrared, and nuclear magnetic resonance) and elemental analysis of the complex are discussed. This complex shows greater growth inhibitory activity against human tumor cell line K562 than cisplatin. Results of UV-visible studies show that the complex exhibits cooperative binding with DNA and denatures the DNA at an extremely low concentration (∼11.98 μM). Fluorescence studies reveal that the mode of binding of this complex with DNA seems to be intercalation. The results of sephadex G-25 column show that the binding of metal complex with DNA is so strong that it does not readily break. Several binding and thermodynamic parameters are also described. They may shed light on the mechanisms of interaction of this agent with DNA, which should be quite different from that of cisplatin.

Interaction studies between a 1,10-phenanthroline adduct of palladium(II) dithiocarbamate anti-tumor complex and calf thymus DNA. A synthesis spectral and in-vitro study

The interaction of calf thymus DNA (CT-DNA) with a novel synthesized and characterized Palladium (II) complex with the formula of [Pd (Et-dtc) (phen)] NO(3) (where phen is 1,10-phenanthroline and Et-dtc is ethyldithiocarbamate) was extensively studied by various spectroscopic techniques. UV-vis studies imply that there is a set of 6 binding sites for the complex on DNA with positive cooperativity in the binding process. This complex unexpectedly denatures the DNA at very low concentration (approximately 9.8 microM). Gel filtration studies indicate that the binding of metal complex with DNA is strong enough not to readily break. Fluorescence studies show that the palladium complex intercalates in DNA through the planar 1,10-phenanthroline ligand presented in its structure. Several binding and thermodynamic parameters are also described. Furthermore, anti-tumor studies of this water soluble complex against human cell tumor lines (K562) have been done. It shows 50% cytotoxic concentration (Ic(50)) value much lower than that of cisplatin.

Design, synthesis, and biological evaluation of a new palladium(II) complex: beta-lactoglobulin and K562 as targets

A water-soluble Pd(II) complex (2,2'-bipyridinglycinato Pd(II) nitrate) has been synthesized and characterized. The effect of synthesized complex on the carrier model protein structure and cell proliferation was investigated. Whey carrier protein beta-lactoglobulin-B (BLG-B) and chronic myelogenous leukemia cell line K562 were the targets. Fluorescence and CD instruments were used to assess effect of the complex on the protein structure at different temperatures. Growth inhibitory and apoptotic effect of the Pd(II) complex toward the cancer cells was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. This complex exhibited potent cytotoxic properties against chronic myelogenous leukemia cell line K562. The cells showed different sensitivity to complex. Cytotoxic studies shown that Pd(II) complex induced apoptosis of K562 cells in a concentration and time dependent manner. Then, it might be concluded that Pd(II) complex is a promising antiproliferative agent and should execute its biological effects by inducing apoptosis. Results of fluorescence studies revealed that Pd(II) complex can quench the intrinsic fluorescence emission of the protein at different temperatures. The far- and near-UV CD studies displayed that the Pd(II) complex induces changes in the secondary and tertiary structures of BLG-B at different temperatures. The biological significance of this work is evident since BLG serves as a carrier molecule for several antitumor compounds. Therefore, the interaction of the Pd(II) complex (with antitumor activity) can provide useful information to better design metal anticancer complexes with fewer side effects.

Antiproliferative effect and genotoxicity of novel synthesized palladium complexes with organoarsenic ligands

Three new palladium complexes with general formula [PdCl(2)L(2)], where L=heterofunctional organoarsenic ligand: (2-isopropoxyphenyl)diphenylarsine (1), (2-methoxyphenyl)-diphenylarsine (2) and (2-hydroxyphenyl)diphenylarsine (3) have been synthesized and fully characterized, including X-ray crystallographic data. Their potential antitumor effect and genotoxicity have been studied as well. The viability test performed on human tumor (MLS) and normal (Hfl-1) cell lines indicates significant cytotoxicity of complexes, which is higher in tumor cells than in normal cells. The lethal doses are comparable with those of standard metal-based chemotherapeutical drugs (carboplatin and oxaliplatin). These palladium complexes exhibit a higher cytotoxicity against tumor cells as against normal cells in vitro. A new static cytometric method was developed and simultaneously the classic AnnexinV test was performed. Complex 2 has an important capacity to induce apoptosis in tumor cells. The apoptotic process is triggered due to the interaction of these complexes with secondary structure of DNA in treated cells. The alkaline single-cell gel assay shows that the level of DNA damages induced by compounds 2 and 3 are significantly higher in tumor cells as in normal cells. These studies shown that complexes 1, 2 and 3 have biologic activity, the effect of complex 2 being superior to its platinum analogues, attributable to its structure.