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

Preliminary anticancer evaluation of new Pd(II) complexes bearing NNO donor ligands

In this study we presented a novel series of NNO tridentate ligands generating imino, amido and oxo donor pocket for Pd(II) coordination. All the compounds were meticulously characterized by elemental analysis and advanced spectroscopic techniques, including FTIR, proton and carbon NMR. The synthesized compounds underwent rigorous evaluation for their potential as anti-cancer agents, utilizing the aggressive breast cancer cell lines MDA-MB (ATCC) and MCF-7 as a crucial model for assessing growth inhibition in cancer cells. Remarkably, the MTT assay unveiled the robust anti-cancer activity for all palladium complexes against MDA-MB-231 and MCF-7 cells. Particularly, complex [Pd(L1)(CH3CN)] exhibited exceptional potency with an IC50 value of 25.50 ± 0.30 µM (MDA-MB-231) and 20.76 ± 0.30 µM (MCF-7), compared to respective 27.00 ± 0.80 µM and 24.10 ± 0.80 µM for cisplatin, underscoring its promising therapeutic potential. Furthermore, to elucidate the mechanistic basis for the anti-cancer effects, molecular docking studies on tyrosine kinases, an integral target in cancer research, were carried out. The outcome of these investigations further substantiated the remarkable anticancer properties inherent to these innovative compounds. This research offers a compelling perspective on the development of potent anti-cancer agents rooted in the synergy between ligands and Pd(II) complexes and presenting a promising avenue for future cancer therapy endeavors.

Synthesis, substitution kinetics, DNA/BSA binding and cytotoxicity of tridentate N^E^N (E = NH, O, S) pyrazolyl palladium(II) complexes

The pincer complexes, [Pd(L₁)Cl]BF₄ (PdL₁), [Pd(L₂)Cl]BF₄ (PdL₂), [Pd(L₃)Cl]BF₄ (PdL₃), [Pd(L₄)Cl]BF₄ (PdL₄) were prepared by reacting the corresponding ligands, 2,6-bis[(1H-pyrazol-1-yl)methyl]pyridine (L₁), bis[2-(1H-pyrazol-1-yl)ethyl]amine (L₂), bis[2-(1H-pyrazol-1-yl)ethyl]ether (L₃), and bis[2-(1H-prazol-1-yl)ethyl]sulphide (L₄) with [PdCl₂(NCMe)]₂ in the presence NaBF₄. The solid-state structures of complexes PdL₁-PdL₄ confirmed a tridentate coordination mode, with one chloro ligand completing the coordination sphere to afford square-planar complexes. Chemical behaviour of the complexes in solution confirms their stability in both aqueous and DMSO stock media. The electrochemical properties of the compounds showed irreversible two-electron reduction process. Kinetic reactivity of Pd complexes with the biological nucleophiles viz, thiourea (Tu), L-methionine (L-Met) and guanosine 5'-diphosphate disodium salt (5'-GMP) followed the order: PdL₂ < PdL₃ < PdL₄, and PdL₂ < PdL₁. The kinetic reactivity is subject to the electronic effects of the spectator ligand(s), and the trend was supported by the DFT computed results. The palladium complexes PdL₁-PdL₄ bind to calf thymus (CT-DNA) via intercalation mode. In addition, the bovine serum albumin (BSA) showed good binding affinity to the complexes. The mode of quenching mechanism of the intrinsic fluorescence of CT-DNA and BSA by the complexes was found to be static. The order of interactions of the complexes with DNA and BSA was in tandem with the rate of substitution kinetics. The complexes, however, displayed relatively low cytotoxicity (IC₅₀ > 100 µM) when tested against the human cervical adenocarcinoma (HeLa) cell line and the transformed human lung fibroblast cell line (MRC-5 SV2).

A new palladium-based antiproliferative agent: synthesis, characterization, computational calculations, cytotoxicity, and DNA binding properties

A new palladium(II) complex entitled [Pd(phendione)(8Q)]NO₃, (PdPQ), where phendione is N,N-donor heterocyclic 1,10-phenanthroline-5,6-dion and 8Q is 8-hydroxyquinolinate, has been synthesized and then characterized by molar conductivity, CHN analysis and spectral data (UV-Vis, FT-IR, NMR). DFT/ TDDFT procedures were also performed to determine the electronic structure and the nature of the electronic transitions of PdPQ. Moreover, the affinity and binding properties of DNA to the desired complex have been studied in details using electronic absorption, fluorescence, circular dichroism spectroscopies, and viscosity measurement in combination with molecular docking technique. The obtained results exhibit relatively high DNA binding values with a static quenching mechanism, which suggest that an intercalative mode plays a peridominate role in interaction process concluded by experimental/theoretical measurements. As a result of drug exposure, in vitro cytotoxicity assay demonstrated the antiproliferative activity of the PdPQ against leukemia cancer cell line, K562.

The palladacycle, BTC2, exhibits anti-breast cancer and breast cancer stem cell activity

In women globally, breast cancer is responsible for most cancer-related deaths and thus, new effective therapeutic strategies are required to treat this malignancy. Platinum-based compounds like cisplatin are widely used to treat breast cancer, however, they come with limitations such as poor solubility, adverse effects, and drug resistance. To overcome these limitations, complexes containing other platinum group metals such as palladium have been studied and some have already entered clinical trials. Here we investigated the anti-cancer activity of a palladium complex, BTC2, in MCF-7 oestrogen receptor positive (ER+) and MDA-MB-231 triple negative (TN) human breast cancer cells as well as in a human breast cancer xenograft chick embryo model. BTC2 exhibited an average IC₅₀ value of 0.54 μM, a desirable selectivity index of >2, inhibited the migration of ER+ and TN breast cancer cells, and displayed anti-cancer stem cell activity. We demonstrate that BTC2 induced DNA double strand breaks (increased levels of γ-H2AX) and activated the p-ATM/p-CHK2 and p-p38/MAPK pathways resulting in S- and G2/M-phase cell cycle arrests. Importantly, BTC2 sensitised breast cancer cells by triggering the intrinsic (cleaved caspase 9) and extrinsic (cleaved caspase 8) apoptotic as well as necroptotic (p-RIP3 and p-MLKL) cell death pathways and inhibiting autophagy and its pro-survival role. Furthermore, in the xenograft in vivo model, BTC2 displayed limited toxicity and arrested the tumour growth of breast cancer cells over a 9-day period in a manner comparable to that of the positive control drug, paclitaxel. BTC2 thus displayed promising anti-breast cancer activity.

A novel palladium(II) antitumor agent: Synthesis, characterization, DFT perspective, CT-DNA and BSA interaction studies via in-vitro and in-silico approaches

Since numerous people annually pass away due to cancer, research in this field is essential. Thus a newly made and water like palladium(II) complex of formula [Pd(phen)(acac)]NO₃, where phen is 1,10-phenanthroline and acac is acetylacetonato ligand, has been synthesized by the reaction between [Pd(phen)(H₂O)₂](NO₃)₂ and sodium salt of acetylacetone in the molar ratio of 1:1. It has been structurally characterized via the methods such as conductivity measurement, elemental analysis and spectroscopic methods (FT-IR, UV-Vis and ¹H NMR). The geometry optimization of this complex at the DFT level of theory reveals that Pd(II) atom is situated in a square-planar geometry. The complex has been screened for its antitumor activity against K562 cancer cells which demonstrated efficacious activity. The interaction of above palladium(II) complex with CT-DNA as a target molecule for antitumor agents and BSA as a transport protein was studies by a variety of techniques. The results of UV-Vis absorption and fluorescence emission indicated that the Pd(II) complex interacts with EB + CT-DNA through hydrophobic and with BSA by hydrogen bonding and van der Waals forces at very low concentrations. In these processes, the fluorescence quenching mechanism of both the macromolecules seems to be the combined dynamic and static. The interaction was further supported for CT-DNA by carrying out the gel electrophoresis and viscosity measurement and for BSA by the circular dichroism and Förster resonance energy transfer experiments. Furthermore, results of partition coefficient determination showed that the [Pd(phen)(acac)]NO₃ complex is more lipophilic than that of cisplatin. Moreover, molecular docking simulation confirms the obtained results from experimental tests and reveals that the complex tends to be located at the intercalation site of DNA and Sudlow's site I of BSA.

Structural effects of Diamond nanoparticles and Paclitaxel combination on calf thymus DNA

The combination effects of nanodiamonds (NDs) and Paclitaxel (PTX) on the DNA structure were examined. The UV-Visible, steady-state and time-resolved fluorescence spectroscopy, CD, viscosity and zeta potential results showed that PTX + NDs could form a complex via groove binding mechanism. The values of binding constants, ΔG° and ΔH° and ΔS° values showed that PTX + NDs interact strongly with DNA and the hydrophobic force plays main role in this interaction. The ΔG25ο and T_m study indicated the instability of DNA in presence of PTX + NDs. This study demonstrated that NDs could enhance the effect of PTX on DNA structure as well as its affinity and binding to DNA.

Multiple Spectroscopic, Docking and Cytotoxic Study of a Synthesized 2,2' Bipyridin Phenyl Isopentylglycin Pt(II) Nitrate Complex: Human Serum Albumin and Breast Cancer Cell Line of MDA-MB231 as Targets

In the present study, the biological activities of a new synthesized Pt(II)-complex, 2,2' bipyridinphenyl isopentylglycin Pt(II) nitrate was investigated via its interaction with the most important blood carrier protein of human serum albumin (HSA), using fluorescence and Far-UV circular dichroism (CD) spectroscopic techniques and also molecular docking. Moreover, cytotoxicity activity of the complex was studied against breast cancer cell line of MDA MB231 using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The Pt(II)-complex has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching mechanism. According fluorescence quenching data, the binding parameters of the interaction were calculated and showed that hydrophobic interaction has an important role. The molecular docking results in coherent with fluorescence measurements illustrated that Pt(II) complex can bind to HSA at one position that located in the hydrophobic cavity of groove between drug site I and II. Also, experimental data on driving force in binding site was confirmed whereas theoretical results demonstrated Pt(II) complexinteract to HSA by hydrophobic interaction. Far-UV-CD results showed that Pt(II)-complex induced an increasing in the content of α-helical structure of the protein and stabilized it. Also, MTT assay represented growth inhibitory effect of the complex toward the breast cancer cell line.

A novel mesoionic carbene based highly fluorescent Pd(ii) complex as an endoplasmic reticulum tracker in live cells

Synthesis of new organometallic MIC based mononuclear Pd(ii) complex 1, specifically target ER of live cells and have fluorescence recovery after photobleaching (FRAP) property.

β-Lactoglobulin: An efficient nanocarrier for advanced delivery systems

Thanks to the progress of nanotechnology there are several agent-delivery systems that can be selected to achieve rapid and specific delivery of a wide variety of biologically active agents. Consequently, the manipulation and engineering of biopolymers has become one of the most exciting subjects for those who study delivery systems on the nanoscale. In this regard, both nanoparticle formation and a carrier role have been observed in the case of the globular milk whey protein, β-lactoglobulin (β-LG), setting it apart from many other proteins. To date, many efforts adopting different approaches have created β-LG nanoparticles useful in forming delivery systems for various agents with specific targets. In this review, the potential of β-LG to play the role of an efficient and diverse carrier protein, as well as its ability to form a well-targeted nano-scale delivery system is discussed.

Biological Impact of Pd (II) Complexes: Synthesis, Spectral Characterization, In Vitro Anticancer, CT-DNA Binding, and Antioxidant Activities

A new series of Pd (II) complexes of methyl substituted benzylamine ligands (BLs) has been synthesized and characterized via spectroscopic techniques such as UV/Vis. FTIR, LCMS, ¹H, and ¹³C NMR. The UV/Vis study in DMSO, DMSO + water, and DMSO + PBS buffer (pH = 7.2) confirmed their molecular sustainability in liquids. Their in vitro anticancer activity against breast cancer cell lines such as MCF-7 and MDA-MB-231 makes them interesting for in vivo analysis. Their stronger DNA binding activity (DBA) compared with free ligand suggested them as a good DNA binder. DBA was further confirmed by physicochemical studies such as surface tension and viscosity of complex + DNA which inferred the disruption of DNA and intercalation of complexes, respectively. Their % binding activity, % disruption of DNA base pairs (DNABP), and % intercalating strength are reported in this paper for the first time for better understanding of DNA binding mechanism. Along with this, their scavenging activity (SA) determined through DPPH free radical and the results indicate good antioxidant behaviour of complexes.

Sugar-boronate ester scaffold tethered pyridyl-imine palladium(II) complexes: synthesis and their in vitro anticancer evaluation

A series of five palladium(ii) pyridyl-imine Schiff base complexes 5a-e containing boronate esters with protected sugar diols derived from d-xylose, l-sorbose and d-mannitol were designed and synthesized starting from pyridyl-imines generated in situ from 3-aminophenyl boronate ester of sugars 3a-e and 2-pyridinecarboxaldehyde, followed by the addition of Pd(cod)Cl2 in dichloromethane solvent. All the complexes are remarkably stable orange/yellow crystalline solids and were obtained in good yields. The complexes were fully characterized by FT-IR, multinuclear NMR ((1)H, (13)C and (11)B), UV-visible spectroscopy, and elemental analysis. The solid state structures of 3a and 5a were established by single crystal X-ray diffraction analysis. The complexes have been tested for their in vitro anticancer activities against human colon cancer (HT-29) and breast cancer (MDA-MB-231) cell lines. All the complexes have shown moderate to good cytotoxicity in both the cancer cell lines with IC50 values ranging from 4.27 to 34.76 μM. Strikingly, 5a displayed selective anticancer activity against both HT-29 and MDA-MB-231 cells with low IC50 values 6.71 and 8.58 μM respectively. Results also demonstrate that some of these complexes are highly potent against HT-29 cells as compared to the other cancer cell lines. In particular, 1,2:5,6-di-O-isopropylidene-d-mannitol complex 5d showed a two-fold higher toxicity against HT-29 cells in comparison with that of cisplatin. In addition, these complexes are less toxic to model non-tumorigenic human embryonic kidney cells (HEK-293T). Furthermore, the interaction of the complexes with calf thymus DNA (CT-DNA) was investigated using spectroscopy and viscosity measurements. It was found that they intercalate with DNA.

Fabrication of a pH responsive DOX conjugated PEGylated palladium nanoparticle mediated drug delivery system: an in vitro and in vivo evaluation

Schematic illustration of the possible mechanism of pH based drug delivery system of DOX conjugated PEGylated PdNPs induced apoptosis in HeLa cells.

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.

Differential cytotoxic activity of a novel palladium-based compound on prostate cell lines, primary prostate epithelial cells and prostate stem cells

The outcome for patients with advanced metastatic and recurrent prostate cancer is still poor. Therefore, new chemotherapeutics are required, especially for killing cancer stem cells that are thought to be responsible for disease recurrence. In this study, we screened the effect of a novel palladium-based anticancer agent (Pd complex) against six different prostate cancer cell lines, and primary cultures from seven Gleason 6/7 prostate cancer, three Gleason 8/9 prostate cancer and four benign prostate hyperplasia patient samples, as well as cancer stem cells selected from primary cultures. MTT and ATP viability assays were used to assess cell growth and flow cytometry to assess cell cycle status. In addition, immunofluorescence was used to detect γH2AX nuclear foci, indicative of DNA damage, and Western blotting to assess the induction of apoptosis and autophagy. The Pd complex showed a powerful growth-inhibitory effect against both cell lines and primary cultures. More importantly, it successfully reduced the viability of cancer stem cells as first reported in this study. The Pd complex induced DNA damage and differentially induced evidence of cell death, as well as autophagy. In conclusion, this novel agent may be promising for use against the bulk of the tumour cell population as well as the prostate cancer stem cells, which are thought to be responsible for the resistance of metastatic prostate cancer to chemotherapy. This study also indicates that the combined use of the Pd complex with an autophagy modulator may be a more promising approach to treat prostate cancer. In addition, the differential effects observed between cell lines and primary cells emphasise the importance of the model used to test novel drugs including its genetic background, and indeed the necessity of using cells cultured from patient samples.

Calorimetric and Spectroscopic investigations οf β-lactoglobulin upon interaction with copper ion

The effect of copper(II) ions (Cu+2) on the structure of β-lactoglobulin (β-lg) was investigated spectroscopically using UV-visible, fluorescence and circular dichroism (CD) and calorimetrically using isothermal titration calorimetry (ITC), at different temperatures. Results of the UV-visible studies showed that adding Cu+2 to β-lg solution caused increasing turbidity, indicative of protein aggregation. It was noticeable that the rate of increasing turbidity was directly proportional to increasing temperature. The far-UV CD studies displayed that the Cu+2 cannot induce any significant changes in the secondary structures of β-lg at different temperatures. Also, the ITC data indicated that the binding process of Cu+2 to β-lg is mainly entropically driven. The results highlight that copper ions cause the tertiary structure of β-lg to change and induce a slightly open structure leading to the formation of supramolecular aggregates in β-lg which may result in the reduced allergenicity of β-lg and its increased use in industrial applications.

Cell death-inducing effect of novel palladium(II) and platinum(II) complexes on non-small cell lung cancer cells in vitro

PURPOSE

Treatment for lung cancer is still far from satisfying rates. Therefore, there is a need for novel anticancer agents. For this purpose, novel platinum and palladium complexes {[Pd(sac)(terpy)](sac)·4H(2)O (Complex 1), [Pt(sac)(terpy)](sac)·5H(2)O (Complex 2), [PdCl(terpy)](sac)·2H(2)O (Complex 3), [PtCl(terpy)](sac)·2H(2)O (Complex 4)} have been tested against three different non-small cell lung cancer cell lines (A549, H1299, PC-3).

METHODS

Growth-inhibiting effects have been tested by the MTT and ATP viability assays. Apoptosis has been detected by the caspase-cleaved cytokeratin 18 (M30-antigen) assay. Necrosis has been detected by staining the cells with fluorescent dyes. Mitotic index has been calculated by counting the mitotic figures after staining with hematoxylin.

RESULTS

The complex 3 exhibited significant anti-growth effects, and its anti-growth effect was more powerful than that of cisplatin that is a standard chemotherapeutic agent for this type of cancer. The complexes did not induce apoptosis, while necrosis clearly took place.

CONCLUSIONS

Novel Pd(II) complex ([PdCl(terpy)](sac)·2H(2)O) seems to represent a potentially active drug against non-small cell lung cancer cell lines, and further studies in vivo are warranted.