In vitro cytotoxicity studies of palladacyclic complexes containing the symmetric diphosphine bridging ligand. Studies of their interactions with DNA and BSA

Preparation and characterization of cetuximab-loaded egg serum albumin nanoparticles and their uses as a drug delivery system against Caco-2 colon cancer cells

To avoid the harmful side effects of cetuximab and improve its therapeutic efficacy, egg serum albumin (ESA) was used as a targeting drug carrier moiety for cancer therapy against Caco-2 colon cancer cells. The simple improved desolvation method was used to synthesize ESA nanoparticles (ESA-NPs) and cetuximab-loaded albumin nanoparticles (CET-ANPs) with glutaraldehyde as a crosslinking agent. The ESA-NPs and CET-ANPs were spherically shaped, and their sizes and surface potentials were 100 and − 24 nm and 170 and − 20 nm, respectively, as determined using transmission electron microscopy (TEM) and a Zeta potential analyzer. The specific functional groups of the prepared nanoparticles were revealed by FTIR analysis. In the MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay, CET-ANPs exerted the highest antitumor activity after 24 h followed by CET, ESA-NPs, and pure ESA. Combination of CET + ESA-NPs at different IC50 concentrations at ratios of 1:1, 1:2, 2:1, 1:4, 4:1, 1:9, or 9:1 showed significant synergistic effects with a combination index (CI) > 1. Furthermore, the CET either loaded with ESA-NPs or administered in combination (CET + ESA NPs) caused significant apoptotic damage, as well as an S-phase or G2/M cell cycle arrest to the cancer cells, respectively. These were directly linked with a significant upregulation of mRNA expression of Caspase3 and Bax genes and an extreme downregulation of the mRNA expression of Bcl2, particularly in the combination treatment group, as compared to the untreated cells. Finally, ESA-NPs improved the effectiveness of cetuximab, strongly caused apoptotic and antiproliferative action with lower systemic toxicity, and could be suggested for the targeted administration of anticancer medications in various nanosystems.

Study of novel bidentate heterocyclic amine-based metal complexes and their biological activities: cytotoxicity and antimicrobial activity evaluation

Metallic antitumor drugs with heterocyclic ligands, such as novel AMI (amino methyl imidazole) complexes [Pd(AMI)Cl₂](1), [Cu(AMI)L¹](2), and [Cu(AMI)L²·2H₂O](3) where L¹ = oxalate and L² = malonate, were synthesized and characterized. Assessments included elemental analyses, mass spectrometry, Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy, and thermal analysis. The cytotoxicity of AMI complexes compared to cisplatin was assessed using MTT (3-[4,5-dimethylthiazol-2-yl] 2,5diphenyl tetrazolium bromide) assay with breast (MCF-7) and cervical (HeLa) cancer cell lines. After treating these cells with the AMI complexes' IC₅₀ values for 48 h, malondialdehyde levels and catalase activity were used to assess oxidative stress, antioxidant activity was evaluated with DPPH radical scavenging method, comet assays assessed DNA damage, and DNA fragmentation was evaluated using the gel electrophoresis. In vitro, antimicrobial activity was assessed using a disc diffusion method. The anticancer activity results showed that IC₅₀ (half-maximal inhibitory concentration) values of complex one, two, and three against MCF-7 and HeLa cancer cells are 0.156 ± 0.0006, 0.125 ± 0.001, 0.277 ± 0.002 μM respectively for MCF-7 cells and 0.222 ± 0.0005, 0.126 ± 0.0009, 0.152 ± 0.001 μM respectively for HeLa cells. Complex two demonstrated strong anticancer activity against MCF-7 and Hela cells. The study of oxidative stress parameters revealed that Malondialdehyde levels increased in cancer cell lines treated with complexes compared to untreated cells. Catalase activity decreased in cells treated with palladium chelate. The DPPH radical scavenging assay results identified that complex one was a more potent antioxidant in MCF-7 and Hela cells than other complexes with SC₅₀ values of 227.5 ± 0.28 and 361 ± 1.2 μL/mL, respectively. The comet assay results showed that complex two caused significant DNA damage in MCF-7 and HeLa cancer cells treated. Antimicrobial assays identified complex three as the most effective. Copper complexes give better antifungal activity against A. flavus than the palladium complex. We conclude that complex two is the most active in both cell types and might be assessed as a clinically useful drug for breast cancer treatment. The significance of the current study is the synthesis of antitumor drugs containing heterocyclic ligands, such as novel AMI complexes, and the study of their biological activities.

Study on the interaction of two quinazoline derivatives as novel PI3K/mTOR dual inhibitors and anticancer agents to human serum albumin utilizing spectroscopy and docking

Interactions of human serum albumin (HSA) with two structurally similar quinazoline derivatives, S₁ and S₂ , which are potential anticancer drugs acting on PI3K/mTOR targets, were investigated in vitro utilizing multiple spectroscopy as well as molecular docking. The fluorescence quenching study demonstrated that HSA fluorescence could be statically quenched by S₁ and S₂ through the formation of an HSA-drug complex. Furthermore, the details of the binding site number, binding constant, as well as the thermodynamic parameters, were estimated at 298, 303, and 310 K. The results revealed that hydrogen bond interactions, as well as van der Waals forces, were the predominant factors responsible for binding HSA to S₁ or S₂ . Synchronous fluorescence and ultraviolet (UV) absorption spectra suggested that S₁ and S₂ had little effect on the polarity of the microenvironment and conformation of HSA. Energy transfer from HSA to S₁ or S₂ most probably occurred. The docking study revealed that S₁ and S₂ were able to bind to the hydrophobic cavity that was located in the HSA subdomain IIA and formed varying numbers of hydrogen bonds with amino acid residues nearby. Due to the subtle difference in the chemical structure, the binding of S₁ and S₂ to HSA was slightly different.

Mechanistic insights into the anti-cancer activity of the PEGylated binuclear palladacycle, BTC2, against triple-negative breast cancer

Triple-negative breast cancer (TNBC) has a low five-year survival rate, especially if the cancer is diagnosed at a late stage and has already metastasized beyond the breast tissue. Current chemotherapeutic options for TNBC rely on traditional platinum-containing drugs like cisplatin, oxaliplatin and carboplatin. Unfortunately, these drugs are indiscriminately toxic, resulting in severe side effects and the development of drug resistance. Palladium compounds have shown to be viable alternatives to platinum complexes since they are less toxic and have displayed selectivity towards the TNBC cell lines. Here we report the design, synthesis, and characterization of a series of binuclear benzylidene palladacycles with varying phosphine bridging ligands. From this series we have identified BTC2 to be more soluble (28.38-56.77 μg/mL) and less toxic than its predecessor, AJ5, while maintaining its anticancer properties (IC₅₀ (MDA-MB-231) = 0.58 ± 0.012 μM). To complement the previous cell death pathway study of BTC2, we investigated the DNA and BSA binding properties of BTC2 through various spectroscopic and electrophoretic techniques, as well as molecular docking studies. We demonstrate that BTC2 displays multimodal DNA binding properties as both a partial intercalator and groove binder, with the latter being the predominant mode of action. BTC2 was also able to quench the fluorescence of BSA, thereby suggesting that the compound could be transported by albumin in mammalian cells. Molecular docking studies revealed that BTC2 is a major groove binder and binds preferentially to subdomain IIB of BSA. This study provides insight into the influence of the ligands on the activity of the binuclear palladacycles and provides much needed information on the mechanisms through which these complexes elicit their potent anticancer activity.

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).

Discrimination of non-infectious SARS-CoV-2 particles from fomites by viability RT-qPCR

The ongoing coronavirus 2019 (COVID-19) pandemic constitutes a concerning global threat to public health and economy. In the midst of this pandemic scenario, the role of environment-to-human COVID-19 spread is still a matter of debate because mixed results have been reported concerning SARS-CoV-2 stability on high-touch surfaces in real-life scenarios. Up to now, no alternative and accessible procedures for cell culture have been applied to evaluate SARS-CoV-2 infectivity on fomites. Several strategies based on viral capsid integrity have latterly been developed using viability markers to selectively remove false-positive qPCR signals resulting from free nucleic acids and damaged viruses. These have finally allowed an estimation of viral infectivity. The present study aims to provide a rapid molecular-based protocol for detection and quantification of viable SARS-CoV-2 from fomites based on the discrimination of non-infectious SARS-CoV-2 particles by platinum chloride (IV) (PtCl₄) viability RT-qPCR. An initial assessment compared two different swabbing procedures to recover inactivated SARS-CoV-2 particles from fomites coupled with two RNA extraction methods. Procedures were validated with human (E229) and porcine (PEDV) coronavirus surrogates, and compared with inactivated SARS-CoV-2 suspensions on glass, steel and plastic surfaces. The viability RT-qPCR efficiently removed the PCR amplification signals from heat and gamma-irradiated inactivated SARS-CoV-2 suspensions that had been collected from specified surfaces. This study proposes a rapid viability RT-qPCR that discriminates non-infectious SARS-CoV-2 particles on surfaces thus helping researchers to better understand the risk of contracting COVID-19 through contact with fomites and to develop more efficient epidemiological measures.

Homo and heterobimetallic palladium and platinum complexes bearing μ-diphosphane bridges involved in biological studies

Given the increasing reports of well-defined bimetallic molecular complexes as potential anticancer agents in the last decades, along with the prevalence of platinum in anticancer therapy, we report here a detailed survey of bimetallic platinum and palladium complexes investigated as potential anticancer agents. Specifically, we will concentrate on the synthesis, characterisation and biological (anticancer) studies of a sub-class of these agents, namely homo and heterobimetallic complexes bearing a bridging phosphane ligand of the type: [L_nM₁(μ-R₂P(CH₂)_nPR₂)M₂L_m] (where M₁ is platinum or palladium, M₂ is any other transition metal, R = alkyl or aryl substituents, L_n or L_m are co-ligands, n = 1-6). We will review the in vitro and in vivo activities and any mechanistic anticancer studies of these complexes with a view of trying to delineate patterns in biological activity and structure-activity relationships (SAR). We do not include the review of bimetallic complexes in this class that have not undergone any anticancer testing, nor those that have been involved in other biological investigations unrelated to cancer studies.

Multispectral and molecular modeling investigations on the binding behaviors of two anticoccidials with serum albumins

The interaction properties of monensin/clopidol with bovine/human serum albumin (BSA/HSA) were determined via multispectral together with molecular modeling techniques in the report. Fluorescence quenching spectra at different temperatures and fluorescence lifetime determination demonstrated that the fluorescence quenching belonged to a static quenching type. In the case of monensin-BSA, clopidol-BSA, monensin-HSA and clopidol-HSA, the binding constants K_a (291 K) were 5.42 × 10⁴, 4.96 × 10⁴, 3.22 × 10⁴ and 2.99 × 10⁴ M^-1, respectively; the binding distances r₀ were 1.88, 2.53, 2.19 and 2.02 nm, respectively. Monensin and clopidol bound strongly with BSA/HSA with binding free energies equal to -26.37/-25.11 and -26.11/-24.93 kJ mol^-1, respectively. The spontaneous binding process was dominated by hydrogen bonds and van der Waals forces as reflected in thermodynamic parameters analyses. Synchronous, CD, FTIR and UV-vis spectra assays confirmed that serum albumins conformations were altered. Using competitive experiment, monensin/clopidol was observed to bind at site I of serum albumins, which were reconfirmed by the results of molecular modeling.Communicated by Ramaswamy H. Sarma.

Experimental and theoretical studies of Palladium-hydrazide complexes' interaction with DNA and BSA, in vitro cytotoxicity activity and plasmid cleavage ability

New palladium complexes with general formula trans-[Pd(L)₂(OAc)₂] (1,2), (L = Benzhydrazide and 2-Furoic hydrazide) have been synthesized and characterized with various methods including elemental analysis, FT-IR, ¹HNMR and mass spectroscopy. Afterward their interactions with bovine serum albumin and calf thymus deoxyribonucleic acid have been investigated by UV-vis absorption, fluorescence emission and circular dichroism spectroscopy. Also, site-selective replacement experiments with site probes have been carried out. Analysis of fluorescence spectrum indicated static quenching mechanism. Spectroscopic measurements for DNA binding showed the groove binding to DNA for both complexes. Furthermore, cytotoxicity studies of complexes and cis-platin have been done against colon carcinoma (CT26) and breast cancer (4T1) cell lines. Evaluation of complexes (1) and (2) on induction of apoptosis in CT26 cells has been done. Finally, plasmid cleavage ability of (1) and (2) was investigated by gel electrophoresis that indicate the more activity of (1) than (2).

Novel P,C-orthopalladated complexes containing histidine and phenylalanine amino acids: synthesis, DNA and BSA interactions, in vitro antitumoral activity and molecular docking approach

Novel [Pd(o-CH₂C₆H₄P(o-tolyl)₂)(histidine)] (1) and [Pd(o-CH₂C₆H₄P(o tolyl)₂)(phenylalanine)] (2) P,C-orthopalladated complexes have been prepared and characterized by elemental analysis, IR and NMR spectroscopy. To study the stability of the compounds in biological media, the complexes were incubated in Tris buffer during 10 days. The absorbance of the compounds remained constant, which confirmed the stability of the complexes in biological media. UV-Vis absorption spectrophotometry, fluorescence spectroscopy and viscosity studies were used to investigate the binding of the complexes with native calf thymus DNA (CT-DNA). These methods along with competitive binding of methylene blue (MB) DNA show that the complexes interact with DNA via groove mode. The UV-Vis absorption spectrophotometry of BSA with complexes has shown an α-helix perturbation induced by a particular interaction between the metal complexes and BSA. In addition, the fluorescence quenching mechanism of BSA with the complexes is a static process, according to the fluorescence spectrometry of bovine serum albumin (BSA). The experimental results of site competitive replacement with specific site markers are clear indications that the complexes bind to site I of BSA. Furthermore, both complexes showed significant selective cytotoxic activity against melanoma B16F0 and colon carcinoma C26 cancer cells as well as normal fibroblast NIH cell line. Ultimately, the binding of Pd(II) complexes to DNA and BSA was verified by molecular docking experiment.Communicated by Ramaswamy H. Sarma.

Synthesis of 5-(4-(1H-phenanthro[9,10-d]imidazol-2-yl)benzylidene)thiazolidine-2,4-dione as promising DNA and serum albumin-binding agents and evaluation of antitumor activity

A series of phenanthro[9,10-d]imidazole/oxazole and acenaphtho[1,2-d]imidazole with different aryl groups at C2-position has been synthesized. These compounds were in vitro evaluated for antitumor activity against a panel of 60 human cancer cell lines. Compound 8 exhibits higher cytotoxicity towards leukemia, colon, melanoma, renal, and breast cancer cell lines than the other evaluated cell panels and low toxicity against normal cell line Hek293. The binding properties of compound 8 with DNA have been investigated with absorption, emission and circular dichroism as well as thermal denaturation experiments which indicate intercalation with base pairs of human and calf thymus DNA. The molecular docking and site-selective binding studies also reveal the predominant intercalation of compound 8 in base pairs of DNA. The interaction between thiazolidine based phenanthrene 8 and serum albumins (HSA and BSA), transport proteins, has also been explored which shows quenching of fluorescence through static mechanism. The thermodynamic parameters, obtained from van't Hoff relationship indicate the prevalence of hydrogen-bonding/hydrophobic interactions for the binding phenomenon.

Novel Palladium Complex: Cytotoxicity against Cisplatin-resistant K562 Cells

Today, development of resistance to anticancer drugs (including cisplatin) is noticed as a major problem. Recently several studies demonstrated that palladium complexes showed remarkable cytotoxic effects against K562 cell line and could be used efficiently for treatment of many human cancers including leukemia. Hereof, K562 cells were made resistant to cisplatin using increasing concentration of cisplatin up to 4.5 mM and then cytotoxic effect of synthesized palladium complex was evaluated on this sub-line using MTT assay. Annexin V/PI staining using flow cytometry and scanning electron microscopy (SEM) were performed to find out the mechanism of the observed cytotoxicity. Results indicated that tested compounds had a noticeable cytotoxic effect on K562 cells 80 times more than cisplatin. Palladium complex also showed significant cytotoxicity on resistant K562 sub-line. Flow cytometry and SEM results revealed that these compounds exert their cytotoxic effect via apoptosis and it could be concluded that the novel synthesized palladium complex might be a good candidate for replacing cisplatin in case of treatment of cisplatin resistant tumors.

A saccharinate-bridged palladacyclic dimer with a Pd–Pd bond: experimental and molecular docking studies of the interaction with DNA and BSA and in vitro cytotoxicity against human cancer cell lines

The synthesis, characterization and biological activities of a saccharinate-bridged palladacyclic dimer are reported in this work.

Synthesis and spectroscopic characterization study of new palladium complexes containing bioactive O,O-chelated ligands: evaluation of the DNA/protein BSA interaction, in vitro antitumoural activity and molecular docking

[Pd{(C,N)-C₆H₄CH₂NH(Et) (Qu)] (2) and [Pd{(C,N)-C₆H₄CH₂NH(Et) (Nar)] (3) (Qu = Quercetin, Nar = Naringin) mononuclear palladium (II) complexes have been synthesized and characterized using elemental analysis, IR and electronic spectroscopy. The interaction of the prepared complexes with calf thymus DNA and bovine serum albumin (BSA), monitored by UV-visible and fluorescence titrations, respectively, have been carried out to better understand the mode of their action under biological conditions. Intercalative binding mode between the complexes and DNA is suggested by the binding constant (K_b) values of 2.5 × 10⁶ and 3.2 × 10⁶ for complexes 2 and 3, respectively. In particular, the in vitro cytotoxicity of the complexes on two cancer cells lines (bladder carcinoma TCC and breast cancer MCF7) showed that the compounds had broad spectrum, anti-cancer activity with low IC₅₀ values and the order of in vitro anticancer activities is consistent with the DNA-binding affinities. In the meantime, the quenching of tryptophan emission with the addition of complexes using BSA as a model protein indicated the protein binding ability. The quenching mechanisms of BSA by the complexes were static processes, according to the results obtained. The competitive binding using Warfarin, Digoxin and Ibuprofen site markers, which contain definite biding sites, demonstrated that the complexes bind to site I on BSA. Ultimately, the binding sites of DNA and BSA with the complexes have been determined by molecular modelling studies.

A novel Pd(ii) CNO pincer complex of MR (methyl red): synthesis, crystal structure, interaction with human serum albumin (HSA) in vitro and molecular docking

The C–H activation of methyl red (MR) (MR = 2-{[4-(dimethylamino)phenyl]diazenyl}benzoic acid) was achieved by reaction with Pd(OAc)₂under mild conditions.

Innovative Use of Palladium Compounds To Selectively Detect Live Enterobacteriaceae in Milk by PCR

Ethidium monoazide and propidium monoazide (EMA and PMA) have been used in combination with PCR for more than a decade to facilitate the discrimination of live and dead bacteria (LD discrimination). These methods, however, require many laborious procedures, including the use of a darkroom. Here, we demonstrate an innovative use of palladium compounds involving lower limits of detection and quantification of targeted live cells, fewer laborious procedures, lower costs, and potentially higher-throughput analysis than the use of EMA and PMA. We have also recently reported platinum compounds for LD discrimination, but platinum compounds carry costs that are 3 times higher because of the requirement for much larger amounts for LD discrimination than palladium compounds. Palladium compounds can penetrate dead (compromised) but not live bacteria and can be chelated primarily by chromosomal DNA and cell wall transmembrane proteins, with small amounts of DNA-binding proteins in vivo The new mechanism for palladium compounds is obviously different from that of platinum compounds, which primarily target DNA. Combining palladium compounds with PCR (Pd-PCR) in water resulted in discrimination between live and dead Enterobacteriaceae bacteria that was much clearer than that seen with the PMA method. Pd-PCR correlated with reference plating or with the currently used PMA-PCR method for pasteurized milk, based on EN ISO 16140:2003 validation. Pd-PCR enabled us to specifically detect and assay viable Enterobacteriaceae cells at concentrations of 5 to 10 CFU/ml in milk while following U.S./EU regulations after a 4.5-h process in a typical laboratory exposed to natural or electric light, as specified by U.S./EU regulations.IMPORTANCE Ethidium monoazide and propidium monoazide (EMA and PMA) facilitate the discrimination of live and dead bacteria (LD discrimination). These methods, however, require many laborious procedures, including the use of a darkroom. Here, we demonstrate an innovative use of palladium compounds involving fewer laborious procedures, lower costs, and potentially higher-throughput analysis than the use of EMA and PMA. We have also recently reported platinum compounds for LD discrimination, but platinum compounds carry costs that are 3 times higher because of the requirement for much larger amounts for LD discrimination than palladium compounds, which have also a novel reaction mechanism different from that of platinum compounds. In view of testing cost, palladium compounds are also very useful here compared with platinum compounds. Ultimately, the innovative Pd-PCR method may be also substituted for the currently used reference plating methods.