Evaluation of DNA-binding and DNA-photocleavage ability of tetra-cationic porphyrins containing peripheral [Ru(bpy)2Cl]+ complexes: Insights for photodynamic therapy agents

Light exposure of tetra-cationic porphyrins containing peripheral Pd(II)-bipyridyl complexes and the induced effects on purified DNA molecule, fibroblast and melanoma cell lines

Photodynamic therapy (PDT) combines a light source, oxygen, and a photosensitizer (PS) to generate reactive oxygen species (ROS) for treating diseases. In this study, we evaluated two meso-tetra-pyridyl porphyrins with [Pd(bpy)Cl]+, namely 3-PdTPyP and 4-PdTPyP, as PS for PDT application. DNA interaction was assessed by spectroscopic measurements (UV-Vis and fluorescence emission), viscosity analysis, and molecular docking simulations. The results indicate that Pd(II)-porphyrins do not intercalate into DNA, suggesting that the minor groove is the primary interaction site, mainly through van der Waals forces. These metalloporphyrins effectively induced nitrogenous bases oxidation, particularly in purines, after white light irradiation. The induced DNA lesions were able to inactivate plasmid DNA metabolism (DNA replication and transcription) in a bacterial model. 3-PdTPyP and 4-PdTPyP significantly decreased the viability of treated melanoma cell lines (A375 and B16-F10), demonstrating that melanoma cell lines were more sensitive to these Pd(II)-porphyrins than the fibroblast cell line (L929). Moreover, 3-PdTPyP was more photototoxic to A375 cells (IC50 = 0.43 μM), whereas 4-PdTPyP was more photototoxic to B16-F10 cells (IC50 = 0.51 μM). These findings suggest that these porphyrins are promising PS for future PDT research focused on skin cancer.

Spectroscopic investigation and structural simulation in human serum albumin with hydroxychloroquine/Silybum marianum and a possible potential COVID-19 drug candidate

In this study, the interaction between human serum albumin (HSA) and the hydroxychloroquine/Silybum marianum (HCQ/SM) mixture was investigated using various techniques. The observed high binding constant (Kb) and Stern-Volmer quenching constant (KSV) indicate a strong binding affinity between the HCQ/SM mixture and HSA. The circular dichroism (CD) analysis revealed that HCQ/SM induced conformational changes in the secondary structure of HSA, leading to a decrease in the α-helical content. UV-Vis analysis exhibited a slight redshift, indicating that the HCQ/SM mixture could adapt to the flexible structure of HSA. The experimental results demonstrated the significant conformational changes in HSA upon binding with HCQ/SM. Theoretical studies were carried out using molecular dynamics simulation via the Gromacs simulation package to explore insights into the drug interaction with HSA-binding sites. Furthermore, molecular docking studies demonstrated that HCQ/SM-HSA exhibited favorable docking scores with the receptor (5FUZ), suggesting a potential therapeutic relevance in combating COVID-19 with a value of -6.24 kcal mol-1. HCQ/SM exhibited stronger interaction with both SARS-CoV-2 virus main proteases compared to favipiravir. Ultimately, the experimental data and molecular docking analysis presented in this research offer valuable insights into the pharmaceutical and biological properties of HCQ/SM mixtures when interacting with serum albumin.

The photophysical, photobiological, and DNA/HSA-binding properties of corroles containing carbazole and phenothiazine moieties

This study characterized four corrole derivatives, namely Cbz-Cor, MetCbz-Cor, PTz-Cor, and PTzEt-Cor, examining their photophysical, electrochemical, photobiological, and biomolecule-binding properties. Experimental photophysical data of absorption and emission elements correlated with a theoretical analysis obtained through time-dependent density functional theory (TD-DFT). As for the photophysical properties, we observed lower fluorescence quantum yields and discernible differences between the excited and ground states, as indicated by Stokes shift values. Natural Transition Orbit (NTO) plots presented high occupied molecular orbital - low unoccupied molecular orbital (HOMO-LUMO) densities around the tetrapyrrolic macrocycle in all examples. Our findings demonstrate that corroles maintain stability in solution and offer photostability (<20 %), predominantly in DMSO(5 %)/Tris-HCl (pH 7.4) buffer solution. Furthermore, the singlet oxygen (1O2) quantum yield and log POW values underscore their potential application in photoinactivation approaches, as these corroles serve as effective ROS generators with more lipophilic features. We also evaluated their biomolecular binding capacity towards salmon sperm DNA and human serum albumin using spectroscopic techniques and molecular docking analysis for sustenance. Concerning biomolecule interaction profiles, the corrole derivatives showed a propensity for interacting in the minor grooves of the double helix DNA due to secondary forces, which were more pronounced in site III of the human serum protein.

G-quadruplex in the TMV Genome Regulates Viral Proliferation and Acts as Antiviral Target of Photodynamic Therapy

Plant viruses seriously disrupt crop growth and development, and classic protein-targeted antiviral drugs could not provide complete protection against them. It is urgent to develop antiviral compounds with novel targets. Photodynamic therapy shows potential in controlling agricultural pests, but nonselective damage from reactive oxygen species (ROS) unexpectedly affects healthy tissues. A G-quadruplex (G4)-forming sequence in the tobacco mosaic virus (TMV) genome was identified to interfere the RNA replication in vitro, and affect the proliferation of TMV in tobacco. N-methyl mesoporphyrin IX stabilizing the G4 structure exhibited inhibition against viral proliferation, which was comparable to the inhibition effect of ribavirin. This indicated that G4 could work as an antiviral target. The large conjugate planes shared by G4 ligands and photosensitizers (PSs) remind us that the PSs could work as antiviral agents by targeting G4 in the genome of TMV. Chlorin e6 (Ce6) was identified to stabilize the G4 structure in the dark and selectively cleave the G4 sequence by producing ROS upon LED-light irradiation, leading to 92.2% inhibition against TMV in vivo, which is higher than that of commercial ningnanmycin. The inhibition of Ce6 was lost against the mutant variants lacking the G4-forming sequence. These findings indicated that the G-quadruplex in the TMV genome worked as an important structural element regulating viral proliferation, and could act as the antiviral target of photodynamic therapy.

Molecular docking and spectroscopic study of bovine serum albumin interaction with new anticancer Pt complex with isopentyl dithiocarbamate ligand

Although cisplatin is useful in the treatment of cancer, it has a series of side effects that limit its use. Dithiocarbamates reduce the toxicity of platinum due to their structure and the presence of S, and N donating groups. In this article, the interaction of [Pt(bpy)(isopentyl.dtc)]NO3, where bpy is bipyridine and isopentyl.dtc is isopentyl-dithiocarbamate, with BSA, bovine serum albumin has been studied. The molecular binding method, including UV-Vis and fluorescence titration, was carried out in conditions including pH = 7.4 and temperatures of 27 and 37 °C. The negative values of enthalpy (ΔH°b) and entropy (ΔS°b) show that the driving forces of this interaction are hydrogen and van der Waals, and the negative value of the Gibbs free energy, ΔG°b indicates that the interaction proceeds spontaneously. The fluorescence results showed that the quenching mechanism is the static type and the Stern Volmer constant, KSV, was also obtained. The fluorescence titration method data displayed that the quenching mechanism is static. Binding constant (Kb), binding point (n), Hill coefficients, nH, Hill constant, KH, number of binding sites, g, BSA melting temperature, Tm, were also obtained. Finally, the molecular docking method result shows the binding constant, Ki and binding free energy for the platinum complex are -6.53 and 16.39 kcal mol-1, respectively, and also the proper position of binding on BSA can be considered the site I in the subdomain IIA.

DNA-Interactive and Damage Study with meso-Tetra(2-thienyl)porphyrins Coordinated with Polypyridyl Pd(II) and Pt(II) Complexes

We report the DNA-binding properties of three porphyrins with peripheral thienyl substituents (TThPor, PdTThPor and PtTThPor). The binding capacity of each porphyrin with DNA was determined by UV-Vis and steady-state fluorescence emission spectroscopy combined with molecular docking calculations. The results suggest that the interaction of these compounds probably occurs via secondary interactions via external grooves (minor grooves) around the DNA macromolecule. Moreover, porphyrins containing peripheral Pd(II) or Pt(II) complexes (PdTThPor and PtTThPor) were able to promote photo-damage in the DNA.

The interaction mechanism of candidone with calf thymus DNA: A multi-spectroscopic and MD simulation study

In this investigation, the effects of candidone on the structure and conformation of DNA were evaluated by spectroscopic methods, molecular dynamics simulation, and molecular docking studies. Fluorescence emission peaks, ultraviolet-visible spectra, and molecular docking exhibited the complex formation between candidone and DNA in a groove-binding mode. Fluorescence spectroscopy results also showed a static quenching mechanism of DNA in the presence of candidone. Moreover, thermodynamic parameters demonstrated that candidone spontaneously bound to DNA with a high binding affinity. The hydrophobic interactions were the dominant forces over the binding process. Based on the Fourier transform infrared data candidone tended to attach to the A-T base pairs of the minor grooves of DNA. The thermal denaturation and circular dichroism measurements displayed that candidone caused a slight change in the DNA structure, which was confirmed by the molecular dynamics simulation results. According to the obtained findings from the molecular dynamic simulation, the structural flexibility and dynamics of DNA were altered to a more extended structure.

Bioactivity, molecular docking and anticancer behavior of pyrrolidine based Pt(II) complexes: Their kinetics, DNA and BSA binding study by spectroscopic methods

The complex [Pt(AEP)Cl₂]; C-1 (where, AEP = 1-(2-Aminoethyl) pyrrolidine) and its hydrolyzed diaqua form cis-[Pt(AEP)(H₂O)₂]²⁺; C-2 were synthesized for their bioactivity and in vitro kinetic study with bioactive thiol group (-SH) containing ligands (like; L- cysteine and N-ac-L- cysteine) for their biological importance for 'drug reservoir' activity. The Thermal Gravimetric Analysis (TGA) was executed to confirm about the weight loss due to coordinated water molecules at high temperature range. At pH 4.0, the substitution behavior of C-2 with the thiols was studied in pseudo-first order reaction condition. The interaction mechanism of thiols with complex C-2 to their corresponding thiol substituted C-3 [Pt(AEP)(L-cys)] and C-4 [Pt(AEP)(N-ac-L-cys)] (where L-cys = L-cysteine and N-ac-L-cys = N-ac-L- cysteine) were proposed from their thermodynamical activation parameters (ΔH^≠ and ΔS^≠), which were obtained from Eyring equation. DNA and BSA binding activity of the complexes C-1 to C-4 were investigated by gel electrophoresis technique, spectroscopic titration and viscosity methods. The binding activity of the complexes with DNA and BSA was evaluated using a theoretical approach molecular docking study. The drug-like nature of the complexes is supported by the prediction of activity spectra for substance (PASS) from 2D structure of the Pt(II) complexes. Structural optimization, HOMO-LUMO energy calculation, Molecular electrostatic potential surface, NBO and TD-DFT calculation were executed by using density functional theory (DFT) with Gaussian 09 software package to pre-assessment of biological activity of the complexes. DFT-based descriptors were determined from the HOMO-LUMA energy to be related with the ability of binding affinity of Pt(II) complexes towards DNA and BSA to the formation of their corresponding adducts. The anticancer property of the design complexes were examined on HCT116 (colorectal carcinoma) cancer cell lines and as well as human normal cell NKE (Normal Kidney Epithelial) and compared with the recognised anticancer drug cisplatin. The Reactive Oxygen Species (ROS) production was assessed by DCFDA assay in presence of the Pt(II) complexes.

A Vanadium(V) complexes derived from pyridoxal/salicylaldehyde. Interaction with CT-DNA/HSA, and molecular docking assessments

With the increasing development of metallopharmaceuticals, coordination compounds become viable alternatives for therapeutic uses. Despite the importance of platinum derivatives in this area, first-row transition metals complexes are welcome due to their characteristics. Vanadium is a promising metal in this context, as it has a range of compounds with different biological applications, including anticancer therapeutic effects. In this effort, the study of interactions between coordination compounds with deoxyribonucleic acid and with human serum albumin is fundamental. In this way, ten iminic ligands were synthesized by condensing p-substituted aromatic benzohydrazides (OH, CH₃, H, NO₂, and NH₂) with salicylaldehyde (L1As-L5As) or pyridoxal hydrochloride (L1P-L5P). These ligands have characteristics that allow the tridentate coordination of vanadium cations, leading to the formation of ten vanadium(V) complexes (C1As-C5As and C1P-C5P) with different structural features, all characterized by single-crystal X-ray diffraction, UV-Vis and infrared spectroscopies, and cyclic voltammetry. In addition, the complexes were tested for their interactions with calf thymus deoxyribonucleic acid and human serum albumin by spectroscopic assays and molecular docking calculations. These new results can contribute to further research and provide different ways to design new vanadium complexes with biological applications.

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.

Rational design of an artificial hydrolytic nuclease by introduction of a sodium copper chlorophyllin in L29E myoglobin

Heme proteins have recently emerged as promising artificial metalloenzymes for catalyzing diverse reactions. In this report, L29E Mb, a single mutant of myoglobin (Mb), was reconstituted by replacing the heme with a sodium copper cholorophyllin (CuCP) to form a new green artificial enzyme (named CuCP-L29E Mb). The reconstituted protein CuCP-L29E Mb was found to exhibit hydrolytic DNA cleavage activity, which was not depending on O₂. In addition, Mg²⁺ ion could effectively promote the DNA cleavage activity of CuCP-L29E Mb. Wild-type (WT) Mb reconstituted with CuCP (named CuCP-WT Mb) did not show DNA cleavage activity under the same conditions. This study suggests that both Mg²⁺ and the ligand Glu29 are critical for the nuclease activity and the artificial nuclease of Mg²⁺-CuCP-L29E Mb may have potential applications in the future.

Comparative Studies on DNA-Binding Mechanisms between Enantiomers of a Polypyridyl Ruthenium(II) Complex

A pair of ruthenium(II) complex enantiomers, Δ- and Λ-[Ru(bpy)₂MBIP]²⁺ (bpy = 2,2'-bipyridine, MBIP = 2-(3-bromophenyl)imidazo[5,6-f]phenanthroline), were designed, synthesized, and characterized. Comparative studies between the enantiomers on their binding behaviors to calf thymus DNA (CT-DNA) were conducted using UV-visible, fluorescence, and circular dichroism spectroscopies, viscosity measurements, isothermal titration calorimetry, a photocleavage experiment, and molecular simulation. The experimental results indicated that both the enantiomers spontaneously bound to CT-DNA through intercalation stabilized by the van der Waals force or the hydrogen bond and driven by enthalpy and that Δ-[Ru(bpy)₂MBIP]²⁺ intercalated into DNA more deeply than Λ-[Ru(bpy)₂MBIP]²⁺ did and exhibited a better DNA photocleavage ability. Molecular simulation further indicated that Δ-[Ru(bpy)₂MBIP]²⁺ more preferentially intercalated between the base pairs of CT-DNA to the major groove, and Λ-[Ru(bpy)₂MBIP]²⁺ more favorably intercalated to the minor groove. These research findings should be very helpful to the understanding of the stereoselectivity mechanism of DNA-bindings of metal complexes, and be useful for the design of novel metal-complex-based antitumor drugs with higher efficacy and lower toxicity.

Nuclease-like metalloscissors: Biomimetic candidates for cancer and bacterial and viral infections therapy

Despite the extensive and rapid discovery of modern drugs for treatment of cancer, microbial infections, and viral illnesses; these diseases are still among major global health concerns. To take inspiration from natural nucleases and also the therapeutic potential of metallopeptide antibiotics such as the bleomycin family, artificial metallonucleases with the ability of promoting DNA/RNA cleavage and eventually affecting cellular biological processes can be introduced as a new class of therapeutic candidates. Metal complexes can be considered as one of the main categories of artificial metalloscissors, which can prompt nucleic acid strand scission. Accordingly, biologists, inorganic chemists, and medicinal inorganic chemists worldwide have been designing, synthesizing and evaluating the biological properties of metal complexes as artificial metalloscissors. In this review, we try to highlight the recent studies conducted on the nuclease-like metalloscissors and their potential therapeutic applications. Under the light of the concurrent Covid-19 pandemic, the human need for new therapeutics was highlighted much more than ever before. The nuclease-like metalloscissors with the potential of RNA cleavage of invading viral pathogens hence deserve prime attention.

meso-Tetra-(4-pyridyl)porphyrin/palladium(II) complexes as anticancer agents

This study reports the synthesis, structural characterization and cytotoxic activity of four new palladium/pyridylporphyrin complexes, with the general formula {TPyP[PdCl(P-P)]₄}(PF₆)₄, where P-P is 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,2-bis(diphenylphosphino)butane (dppb) or 1,1'-bis(diphenylphosphino)ferrocene (dppf). The complexes were characterized by elemental analysis, and by FT-IR, UV/Vis, ¹H and ³¹P{¹H} NMR (1D/2D) spectroscopy. The slow evaporation of a methanolic solution of {TPyP[PdCl(dppb)]₄}(PF₆)₄ (in an excess of NaBF₄ salt) resulted in single crystals suitable for X ray diffraction, allowing the determination of the tridimensional structure of this complex, which crystallized in the P2₁/a space group. The cytotoxicity of the complexes against MDA-MB-231 (breast cancer cells) and MCF-10A (non-tumor breast cancer cells), was determined by the colorimetric MTT method, which revealed that all four complexes show selective indexes close to 1.2, lower than that of cisplatin for the same cells (12.12). The interaction of the complexes with CT-DNA was evaluated by UV-visible and viscosity measurements and it was determined that the complexes interact moderately with CT-DNA, probably by H-bonding/π-π stacking and electrostatic interactions.

Syntheses, crystal structures of two Fe(III) Schiff base complexes with chelating o-vanillin aroylhydrazone and exploration of their bio-relevant activities

Two novel Fe(III) complexes, Fe(HL¹)₂Cl·1.25H₂O (1) and Fe(HL²)₂·Et₃NH·H₂O (2) (H₂L¹ = o-vanillin benzoylhydrazone, H₃L² = o-vanillin salicylhydrazone) are prepared. X-ray single crystal diffraction confirms that the hydrazone ligands can be chelated to iron centre resulting in a six-coordinate octahedral configuration. Both complexes show major intercalation effect to the herring sperm deoxyribonucleic acid (HS-DNA) with high binding constants of 2.01 × 10⁴ M^-1 and 2.24 × 10⁴ M^-1, respectively. Molecular docking studies reveal both complexes can intercalate at the gap of DC5-DG2 and DG6-DC1 base pairs of DNA hexamer (1Z3F). The interaction of the complex 1 with plasmid pBR322 DNA induces distinguishable alterations of the DNA morphology. Further, the structure of plasmid pBR322 DNA treated with complex 1 in the presence of ascorbic acid has been damaged probably due to the reactive oxygen species (ROS) generation. What's more, both complexes show high affinity with bovine serum albumin (BSA), the binding constants measured by fluorescence techniques are 5.75 × 10⁶ M^-1 and 4.39 × 10⁷ M^-1, respectively. Molecular docking demonstrates that the complexes prefer the binding pocket of site III (subdomain IIB) of BSA (PDB ID: 4F5S). Similarly, dynamic light scattering (DLS) reveals that the complexes not only bind to BSA but also induce bigger size aggregates as the concentration increases.

Halogenated Gallium Corroles:DNA Interaction and Photodynamic Antitumor Activity

A series of halogenated gallium corroles were synthesized and characterized by UV-vis, HRMS, NMR, and FT-IR. The interaction between these gallium corroles and calf thymus DNA had been investigated by spectroscopic methods. These gallium corroles would interact with CT-DNA via an outside binding mode. The photodynamic antitumor activity in vitro of these gallium corroles toward different cell lines had also been tested. 3-Ga displayed low cytotoxicity to normal cells under both light and dark conditions but high phototoxicity to liver cancer cells HepG2. The vitro experiment results showed that 3-Ga could be efficiently absorbed by tumor cells. After light illumination, it may induce reactive oxygen species (ROS) and cause destruction of the mitochondrial membrane potential, which may finally trigger tumor cell apoptosis. Flow cytometry results showed that HepG2 cells were mainly distributed in the sub-G0 phase, which corresponds to cells with highly fragmented DNA or dead cells generally. This suggests that 3-Ga could lead to tumor cell apoptosis after light illumination.