In vitro DNA binding studies of antiretroviral drug nelfinavir using ethidium bromide as fluorescence probe

Re(I)[2-aryl-1H-imidazo[4,5-f][1,10]phenanthroline] tricarbonyl chloride complexes for selective cancer therapy via a potential DNA damage mechanism

Recently, achieving selective cancer therapy with trifling side effects has been a great challenge in the eradication of cancer. Thus, to amplify the cytoselective approach of complexes, herein, we developed a series of Re(I)[2-aryl-1H-imidazo[4,5-f][1,10]phenanthroline] tricarbonyl chloride complexes and screened their potency against HeLa and MCF-7 cell lines together with the evaluation of their toxicity towards a normal kidney cell line (HEK-293). On meticulous investigation, complex [ReI(CO)3Cl(K2-N,N-(2c))] (3c) was found to be the most potent anticancer entity among other complexes. Complex 3c also showed competency to induce apoptosis in MCF-7 cells through G2/M phase cell-cycle arrest in association with the generation of ample reactive oxygen species (ROS), eventually leading to DNA intercalation and internucleosomal cleavage. The order of the cytotoxicity of these complexes depended on their lipophilic character and the electron-withdrawing halogen substitution at the para-position of the phenyl ring in the imidazophenanthroline ligand.

Promising Dual Anticancer and Antimetastatic Action by a Cu(II) Complex Derived from Acylhydrazone on Human Osteosarcoma Models

Osteosarcoma cancers are becoming more common in children and young adults, and existing treatments have low efficacy and a very high mortality rate, making it pressing to search for new chemotherapies with high efficacy and high selectivity index. Copper complexes have shown promise in the treatment of osteosarcoma. Here, we report the synthesis, characterization, and anticancer activity of [Cu(N-N-Fur)(NO3)(H2O)] complex where N-N-Fur is (E)-N'-(2-hydroxy-3-methoxybenzylidene)furan-2-carbohydrazide. The [Cu(N-N-Fur)(NO3)(H2O)] complex was characterized via X-ray diffraction and electron spin resonance (ESR), displaying a copper center in a nearly squared pyramid environment with the nitrate ligand acting as a fifth ligand in the coordination sphere. We observed that [Cu(N-N-Fur)(NO3)(H2O)] binds to DNA in an intercalative manner. Anticancer activity on the MG-63 cell line was evaluated in osteosarcoma monolayer (IC50 2D: 1.1 ± 0.1 μM) and spheroids (IC50 3D: 16.3 ± 3.1 μM). Selectivity assays using nontumoral fibroblast (L929 cell line) showed that [Cu(N-N-Fur)(NO3)(H2O)] has selectivity index value of 2.3 compared to cis-diamminedichloroplatinum(II) (CDDP) (SI = 0.3). Additionally, flow cytometry studies demonstrated that [Cu(N-N-Fur)(NO3)(H2O)] inhibits cell proliferation and conveys cells to apoptosis. Cell viability studies of MG-63 spheroids (IC50 = 16.3 ± 3.1 μM) showed that its IC50 value is 4 times lower than for CDDP (IC50 = 65 ± 6 μM). Besides, we found that cell death events mainly occurred in the center region of the spheroids, indicating efficient transport to the microtumor. Lastly, the complex showed dose-dependent reductions in spheroid cell migration from 7.5 to 20 μM, indicating both anticancer and antimetastatic effects.

Biophysical insights on the interaction of anticoagulant drug dicoumarol with calf thymus-DNA: deciphering the binding mode and binding force with thermodynamics

The biological activity of drugs is exhibited due to their interactions with bio-receptors. Dicoumarol (DIC) is a natural hydroxycoumarin and a well-known anticoagulant. DNA is the genetic material and one of the targets of numerous drugs. The interaction of DIC with calf-thymus DNA (ct-DNA) has been studied using different biophysical techniques and docking studies. The binding constant in the order of 103 to 104 M-1 was observed from spectroscopic studies. Thermodynamic studies at 4 different temperatures revealed the spontaneity of the interaction with the entropy-driven process. Marker displacement studies with competitive markers of intercalators (ethidium bromide) and groove binders (Hoechst 33258) confirmed the groove-binding nature of DIC in DNA. The groove-binding mode of DIC was complemented by different studies like viscosity measurements, DNA melting, and the effect of KI on the binding. A minor perturbation in the DNA viscosity and no significant change in the DNA melting temperature (Tm) after binding with DIC further confirms the groove binding mode. The effect of KI on the DIC and DIC-DNA system suggested the absence of DIC intercalation. The absence of significant electrostatic force was revealed from the ionic-strength effect study. Binding-induced conformational variation in ct-DNA was absent in circular dichroism studies. Molecular docking studies suggested the position of DIC within the minor groove of ct-DNA, covering three base pairs long. The outcome of this report may help in understanding the pharmacodynamics and pharmacokinetics of dicoumarol analogs and related molecules.Communicated by Ramaswamy H. Sarma.

Ruthenium-Cyclopentadienyl-Cycloparaphenylene Complexes: Sizable Multicharged Cations Exhibiting High DNA-Binding Affinity and Remarkable Cytotoxicity

Two novel sizable multicharged cationic complexes, of the formulae [(η6--[12]CPP)[Ru(η5--Cp)]12]Χ12 and [(η6--[11]CPP)[Ru(η5--Cp)]11]Χ11, CPP = cycloparaphenylene, Cp = cyclopentadienyl, X = [PF6]-, (1), (3) and [Cl]-, (2), (4), were synthesized and characterized using NMR techniques, high-resolution mass spectrometry, and elemental analyses. Complexes (1) and (3) were stable in acetone and acetonitrile solutions over 48 h. In contrast, the water-soluble (2) and (4) begin to decompose in aqueous media after 1 h, due to the [Cl]- tendency for nucleophilic attack on ruthenium of the {Ru(η5--Cp)} units. Fluorescence quenching experiments conducted during the stability window of (2) with the d(5'-CGCGAATTCGCG-3')2-EtBr adducts revealed remarkably high values for Ksv = 1.185 × 104 ± 0.025 M-1 and Kb = 3.162 × 105 ± 0.001 M-1. Furthermore, the cytotoxic activity of (2) against A2780, A2780res, and MCF-7 cancer cell lines shows that it is highly cytotoxic with IC50 values in the range of 4.76 ± 1.85 to 16 ± 0.81 μΜ.

Synthesis and Characterization of Ruthenium-Paraphenylene-Cyclopentadienyl Full-Sandwich Complexes: Cytotoxic Activity against A549 Lung Cancer Cell Line and DNA Binding Properties

Novel full-sandwich (η5-Cp)-Ru-paraphenylene complexes with the general formula [(η5-Cp)nRu(η6-L)](PF6)n where n = 1-3 and L = biphenyl, p-terphenyl and p-quaterphenyl, were synthesized and characterized by means of spectroscopic and analytical techniques. The structures of the complexes [(η5-Cp)Ru(η6-biphenyl)](PF6) (1), [(η5-Cp)Ru(η6-terphenyl)](PF6) (3) and [(η5-Cp)2Ru(η6-terphenyl)](PF6)2 (4) was determined by X-ray single crystal methods. The interaction of the complexes [(η5-Cp)Ru(η6-quaterphenyl)]Cl, (6)Cl, and [(η5-Cp)2Ru(η6-quaterphenyl)]Cl2, (7)Cl2, with the DNA duplex d(5'-CGCGAATTCGCG-3')2 was studied using NMR techniques. The results showed that both complexes interacted non-specifically with both the minor and major grooves of the helix. Specifically, (6)Cl exhibited partial binding through intercalation between the T7 and T8 bases of the sequence without disrupting the C-G and A-T hydrogen bonds. Fluorometric determination of the complexes' binding constants revealed a significant influence of the number of connected phenyl rings in the paraphenylene ligand (L) on the binding affinity of their complexes with the d(5'-CGCGAATTCGCG-3')2. The complexes (6)Cl and (7)Cl2 were found to be highly cytotoxic against the A549 lung cancer cell line, with complex (6) being more effective than (7) (IC50 for (6)Cl: 17.45 ± 2.1 μΜ, IC50 for (7)Cl2: 65.83 ± 1.8 μΜ) and with a selectivity index (SI) (SI for (6)Cl: 1.1 and SI for (7)Cl2: 4.8).

In vitro and in silico binding studies of phytochemical isochroman with calf thymus DNA using multi-spectroscopic and computational modelling techniques

A wide range of therapeutic molecules uses deoxyribonucleic acid (DNA) as an intracellular target. The interaction of small molecules to DNA is a key feature in pharmacology and plays a vital role in the development of novel and more efficient drugs with increased selective activity and enhanced therapeutic effectiveness. Isochroman (IC) is a constituent of Olea europea plant, which has been shown to exhibit several beneficial pharmacological activities. At present, its interaction studies using calf thymus DNA (ct-DNA) have not been explained. A set of multi-spectroscopic techniques has been performed to determine the interaction mechanism of isochroman with ct-DNA. Absorption spectra and quenching in fluorescence studies show that isochroman and ct-DNA form a complex. The static mode of quenching was determined by the Stern-Volmer plot. The value of binding constant, Kb = 4.0 × 103 M-1 revealed moderate type of binding. Effects of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) and ionic strength were studied to examine the isochroman binding to ct-DNA. Potassium iodide (KI) quenching effects and competitive binding studies clearly showed that isochroman binds in the minor groove of ct-DNA. Circular dichroic and DNA melting experiments also confirmed these results. The experimental outputs were further corroborated via in silico computational modelling studies. Lipinski's rule of 5 and SwissADME showed drug-likeness and oral bioavailability scores. Protox ІІ online software predicts oral and organ toxicity.Communicated by Ramaswamy H. Sarma.

Exploring heterometallic bridged Pt(II)-Zn(II) complexes as potential antitumor agents

The four novel complexes [{cis-PtCl(NH₃)₂(μ-4,4'-bipyridyl)ZnCl(terpy)}](ClO₄)₂ (C1), [{trans-PtCl(NH₃)₂(μ-4,4'-bipyridyl)ZnCl(terpy)}](ClO₄)₂ (C2), [{cis-PtCl(NH₃)₂(μ-pyrazine)ZnCl(terpy)}](ClO₄)₂ (C3) and [{trans-PtCl(NH₃)₂(μ-pyrazine)ZnCl(terpy)}](ClO₄)₂ (C4) (where terpy = 2,2':6',2''-terpyridine) were synthesized and characterized. Acid-base titrations and concentration dependent kinetic measurements for the reactions with biologically relevant ligands such as guanosine-5'-monophosphate (5'-GMP), inosine-5'-monophosphate (5'-IMP) and glutathione (GSH), were studied at pH 7.4 and 37 °C. The binding of the heterometallic bridged cis- or trans-Pt(II)-Zn(II) complexes to calf thymus DNA (CT-DNA) was studied by UV absorption and fluorescence emission spectroscopy and molecular docking. The results indicated that the complexes bind strongly to DNA, through groove binding, hydrogen bonds, and hydrophobic or electrostatic interaction. The possible in vitro DNA protective effect of cis- and trans-Pt-L-Zn complexes has shown that C3 had significant dose-dependent DNA-protective effect and the same ability to inhibit peroxyl as well as hydroxyl radicals. Antiproliferative effect of the complexes, mRNA expression of apoptosis and repair-related genes after treatment in cancer cells indicated that newly synthesized C2 exhibited highly selective cytotoxicity toward colon carcinoma HCT116 cells. Only treatment with trans analog C2 induced effect similar to the typical DNA damaging agent such as cisplatin, characterized by p53 mediated cell response, cell cycle arrest and certain induction of apoptotic related genes. Both cis- and trans-isomers C1 and C2 showed potency to elicit expression of PARP1 mRNA and in vitro DNA binding.

Synthesis, characterization, interactions with the DNA duplex dodecamer d(5'-CGCGAATTCGCG-3')2 and cytotoxicity of binuclear η6-arene-Ru(II) complexes

The novel binuclear η⁶-arene-Ru(II) complexes with the general formula {[(η⁶-cym)Ru(L)]₂(μ-BL)}(PF₆)₄, and their corresponding water soluble {[(η⁶-cym)Ru(L)]₂(μ-BL)}Cl₄, where cym = p-cymene, L = 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen), BL = 4,4'-bipyridine (BL-1), 1,2-bis(4-pyridyl)ethane (BL-2) and 1,3-bis(4-pyridyl)propane (BL-3), were synthesized and characterized. The structure of {[(η⁶-cym)Ru(phen)]₂(μ-BL-1)}(PF₆)₄ was determined by X-ray single crystal methods. The interaction of {[(η⁶-cym)Ru(phen)]₂(μ-BL-i)}Cl₄ (i = 1, 2, 3; (4), (5) and (6) correspondingly) with the DNA duplex d(5'-CGCGAATTCGCG-3')₂ was studied by means of NMR techniques and fluorescence titrations. The results show that complex (4) binds with a K_b = 12.133 × 10³ M^-1 through both intercalation and groove binding, while (5) and (6) are groove binders (K_b = 2.333 × 10³ M^-1 and K_b = 3.336 × 10³ M^-1 correspondingly). Comparison with the mononuclear complex [(η⁶-cym)Ru(phen)(py)]²⁺ reveals that it binds to the d(5'-CGCGAATTCGCG-3')₂ with a K_b value two orders of magnitude lower than (4) (K_b = 0.158 × 10³ M^-1), indicating that for the binuclear complexes both ruthenium moieties participate in the binding. The complexes were found to be cytotoxic against the A2780 and A2780 res. cancer cell line with a selectivity index (SI) in the range of 3.0-5.9.

Deciphering the nature of binding of dexlansoprazole with DNA: Biophysical and docking approaches

Drugs, in general, exhibit their pharmacological activity in binding with intracellular targets. Numerous anticancer and antibacterial drugs target DNA as one of their primary intracellular targets. Dexlansoprazole (DLP) is a heterocyclic compound containing benzimidazole moiety and a proton pump inhibitor used to treat gastroesophageal reflux disease. The interaction of dexlansoprazole with calf thymus DNA (ct-DNA) has been studied using biophysical methods. The UV-Visible studies revealed a binding constant of 2.15 ± 0.3 × 104 M^-1 which is close to the value of 2.44 ± 0.3 × 10⁴ M^-1 obtained from the fluorescence studies. Competitive displacement studies using the fluorescence spectroscopic method with ethidium bromide and Hoechst as DNA markers suggested the groove binding mode of DLP in ct-DNA. The groove binding mode of DLP in ct-DNA was complemented by the results of viscosity and DNA melting studies. Further studies on the effect of ionic strength and potassium iodide on DLP binding with ct-DNA supported the observed binding mode. Circular dichroism studies reflected no significant conformational variation in ct-DNA after the interaction. The binding mode obtained from the experimental studies was corroborated by the molecular docking studies that showed the position of DLP in the minor groove of ct-DNA along with the receptor interface restudies involved in the interaction.

Spectroscopic and molecular modeling methods to investigate the interaction between psycho-stimulant modafinil and calf thymus DNA using ethidium bromide as a fluorescence probe

Interaction type of modafinil with calf thymus DNA (ct-DNA) was examined systematically using ethidium bromide (EB) as a fluorescence probe by fluorescence spectroscopy, UV-Vis spectroscopy, viscosity and molecular docking method. The fluorescence quenching mechanism of ct-DNA-EB by modafinil can be combination of static and dynamic quenching. Results of UV-Vis absorption, competitive binding with Hoechst 33258, ionic strength effect studies, viscosity measurements were confirmed that the interaction type of modafinil with ct-DNA was intercalation. According to docking studies R-modafinil showed better interaction with ct-DNA which is consistent with known pharmacological properties of modafinil. The calculated thermodynamic parameters, enthalpy and entropy change, suggested that the driven forces are hydrogen bonding or van der Walls forces. Results of the docking studies were compatible with the experimental results and confirmed the hydrogen bond formation between modafinil and ct-DNA.

Newly synthesized palladium(II) complexes with aminothiazole derivatives: in vitro study of antimicrobial activity and antitumor activity on the human prostate cancer cell line

Five new complexes of the palladium(II) ion (C1-C5) having the general formula [(PdL₂)]Cl₂ with some 2-aminothiazoles (L1-L5), where L1 = 2-amino-4-(3,4-difluorophenyl)thiazole, L2 = 2-amino-5-methyl-4-phenylthiazole, L3 = 2-amino-4-phenylthiazole, L4 = 2-amino-4-(4-chlorophenyl)thiazole, and L5 = 2-amino-4-(2,4-difluorophenyl)thiazole, have been synthesized and characterized by elemental microanalysis and infrared, ¹H NMR and ¹³C NMR spectroscopy. The in vitro antimicrobial activity of the five ligands and the corresponding Pd(II) complexes is investigated. Testing is performed by the microdilution method and the minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) have been determined. Testing is conducted against 11 microorganisms (nine strains of pathogenic bacteria and two yeast species). The tested ligands and palladium(II) complexes show selective, high and moderate activity. There is a difference in antimicrobial activity between the ligands and the corresponding palladium(II) complexes. The complexes have significant anti-staphylococcal activity and activity on Pseudomonas aeruginosa which is better than the positive control. The interactions of newly synthesized palladium(II) complexes with calf thymus DNA (CT-DNA) were investigated using UV-Vis absorption and fluorescence spectroscopy. Analysis of UV-absorption and fluorescence spectra indicates the formation of a complex between the palladium(II) complexes and DNA. The high values of intrinsic binding constants, K_b, of the order 10⁴ M^-1 and Stern-Volmer quenching constants, K_SV, of the order 10⁵ M^-1 indicated very good binding of all complexes to CT-DNA. Also, the new Pd(II) complexes show high cytotoxic activity towards the human prostate cancer cell line and insignificant activity towards non-cancerous human fibroblasts. Future research could additionally explore the biological activity of Pd(II) complexes presented in this paper and investigate the possibility of their implementation in clinical practice.

Anticancer Activity and Mechanism of Action Evaluation of an Acylhydrazone Cu(II) Complex toward Breast Cancer Cells, Spheroids, and Mammospheres

The purpose of this work was to screen the anticancer activity and mechanisms of action of Cu(II)-acylhydrazone complex [Cu(HL)(H₂ O)](NO₃ )⋅H₂ O, (CuHL), to find a potential novel agent for breast chemotherapies. Cytotoxicity studies on MCF7 cells demonstrated that CuHL has stronger anticancer properties than cisplatin over breast cancer cell models. Computational simulations showed that CuHL could interact in the minor groove of the DNA dodecamer, inducing a significant genotoxic effect on both cancer cells from 0.5 to 1 μM. In this sense, molecular docking and molecular dynamics simulations showed that the compound could interact with 20S proteasome subunits. Also, cell proteasome experiments using breast cancer cells revealed that the complex can inhibit proteasomal activity. Moreover, CuHL induced apoptosis in breast cancer cells at very low micromolar concentrations (0.5-2.5 μM) and displayed relevant anticancer activity over spheroids derived from MCF7 cells. Ultimately, CuHL diminished the number of mammospheres formed, disturbing their morphology and size.

1,2,3-Triazoles of 8-Hydroxyquinoline and HBT: Synthesis and Studies (DNA Binding, Antimicrobial, Molecular Docking, ADME, and DFT)

A new series of 1,2,3-triazole hybrids containing either 2- or 4-hydroxyphenyl benzothiazole (2- or 4-HBT) and naphthalen-1-ol or 8-hydroxyquinoline (8-HQ) was synthesized in high yields and fully characterized. In vitro DNA binding studies with herring fish sperm DNA (hs-DNA) showed that quinoline- and 2-HBT-linked 1,2,3-triazoles of shorter alkyl linkers such as 6a are better with a high binding affinity (3.90 × 105 L mol-1) with hs-DNA as compared to naphthol- and 4-HBT-linked 1,2,3-triazoles bound to longer alkyl linkers. Molecular docking of most active 1,2,3-triazoles 6a-f showed high binding energy of 6a (-8.7 kcal mol-1). Also, compound 6a displayed considerable antibacterial activity and superior antifungal activity with reference to ciprofloxacin and fluconazole, respectively. The docking results of the fungal enzyme lanosterol 14-α-demethylase showed high binding energy for 6a (-9.7 kcal mol-1) involving dominating H-bonds, electrostatic interaction, and hydrophobic interaction. The absorption, distribution, metabolism, and excretion (ADME) parameter, Molinspiration bioactivity score, and the PreADMET properties revealed that most of the synthesized 1,2,3-triazole molecules possess desirable physicochemical properties for drug-likeness and may be considered as orally active potential drugs. The electrophilicity index and chemical hardness properties were also studied by density functional theory (DFT) using the B3LYP/6-311G(d,p) level/basis set.

Unveiling the interaction between PDT active squaraines with ctDNA: A spectroscopic study

Squaraine dyes are potential photosensitizers in photodynamic therapy (PDT) due to their ability to release reactive oxygen species (ROS) and cause DNA damage. For this reason, the evaluation and determination of the type of interaction between squaraines and DNA is of the utmost importance. In this study different spectroscopic techniques such as UV-Vis and fluorescence spectroscopies were used to investigate the type of interaction that occurs between two photosensitizers (halogenated squaraines, i.e. Br-C4 and I-C4) and calf thymus DNA (ctDNA). Squaraines were found to bind ctDNA externally following a minor groove binding as they were able to replace Hoechst (a classic groove binder) from the groove of DNA. This binding mode was further supported by iodide quenching studies, ionic strength assay and Florescence Resonance Energy Transfer. Moreover, association (K_A) and dissociation (K_D) constants were obtained and compared with constants of well-known groove binders.

Insight into the binding mechanism of macrolide antibiotic; erythromycin to calf thymus DNA by multispectroscopic and computational approaches

In the present study, the interactions between Erythromycin drug and calf thymus deoxyribonucleic acid (ct-DNA) were explored by multi spectroscopic techniques (UV-Visible, fluorescence, circular dichroism spectroscopies), viscosity, molecular docking simulation, and atomic force microscopy (AFM). In addition, the values of binding constant were calculated by the UV-Visible and fluorescence spectroscopy. Competitive fluorescence study with methylene blue (MB), acridine orange (AO), and Hoechst 33258 were indicated that the Erythromycin drug could displace the DNA-bound Hoechst, which displays the strong competition of Erythromycin with Hoechst to interact with the groove binding site of DNA. In addition, the observed complexes in AFM analysis comprise the chains of ct-DNA and Erythromycin with an average size of 314.05 nm. The results of thermodynamic parameter calculations (ΔS° = -332.103 ± 14 J mol^-1 K^-1 and ΔH° = -115.839 ± 0.02 kJ mol^-1) approved the critical role of van der Waals forces and hydrogen bonds in the complexation of Erythromycin-DNA. Fluorescence spectroscopy results demonstrate the existence of a static enhancement mechanism in the interaction of Erythromycin-DNA. According to the obtained results, Erythromycin drug interacts with the major groove of ct-DNA. These consequences were further supported by the molecular docking study, and it could be determined that DNA-Erythromycin docked model was in a rough correlation with our experimental results.Communicated by Ramaswamy H. Sarma.

Tetrazolo[1,5-a]quinoline moiety-based Os(IV) complexes: DNA binding/cleavage, bacteriostatic and photocytotoxicity assay

Biological applications of platinum group metal-based complexes have been widely explored in synthetic and inorganic chemistry. The compounds have been subjected to DNA binding, DNA cleavage, In-vivo and In-vitro photocytotoxicity (HCT-116 cell line) and bacteriostatic activities. Binding constant of complexes are 1.42-5.62 × 10⁴ M^-1, whereas that of ligands are 1.12-4.72 × 10⁴ M^-1. K_sv of complexes are about 1.32-5.21 × 10³ M^-1, whereas K_f is about 1.24-6.83 × 10³ M^-1. IC₅₀ of compounds screened using HCT-116 cell line in dark are found to be 121-342 μg/mL. Whereas photocytotoxicity is found in the range of 48-316 μg/mL. Docking energy of molecules have been evaluated to evaluate efficacy of binding. Molecular docking energy of complexes are in the range of -286.00 to -303.11 kJ/mol. Whereas that of ligands are -254.03 to -282.96 kJ/mol. MIC of complexes are 47 ± 2.5 to 77.50 ± 7.5 μM. LC₅₀ values of ligands fall in the range of 4.05-19.72 μg/mL and that of Os(IV) complexes fall in the range of 3.99-15.99 μg/mL. The Os(IV) complexes dominate in proving its potentiality compared to N, N-donor ligands in biological activities. [Formula: see text]Communicated by Ramaswamy H. Sarma.

5-Nitro-Thiophene-Thiosemicarbazone Derivatives Present Antitumor Activity Mediated by Apoptosis and DNA Intercalation

BACKGROUND

Considering the need for the development of new antitumor drugs, associated with the great antitumor potential of thiophene and thiosemicarbazonic derivatives, in this work we promote molecular hybridization approach to synthesize new compounds with increased anticancer activity.

OBJECTIVE

Investigate the antitumor activity and their likely mechanisms of action of a series of N-substituted 2-(5-nitro-thiophene)-thiosemicarbazone derivatives.

METHODS

Methods were performed in vitro (cytotoxicity, cell cycle progression, morphological analysis, mitochondrial membrane potential evaluation and topoisomerase assay), spectroscopic (DNA interaction studies), and in silico studies (docking and molecular modelling).

RESULTS

Most of the compounds presented significant inhibitory activity; the NCIH-292 cell line was the most resistant, and the HL-60 cell line was the most sensitive. The most promising compound was LNN-05 with IC50 values ranging from 0.5 to 1.9 µg.mL-1. The in vitro studies revealed that LNN-05 was able to depolarize (dose-dependently) the mitochondrial membrane, induceG1 phase cell cycle arrest noticeably, promote morphological cell changes associated with apoptosis in chronic human myelocytic leukaemia (K-562) cells, and presented no topoisomerase II inhibition. Spectroscopic UV-vis and molecular fluorescence studies showed that LNN compounds interact with ctDNA forming supramolecular complexes. Intercalation between nitrogenous bases was revealed through KI quenching and competitive ethidium bromide assays. Docking and Molecular Dynamics suggested that 5-nitro-thiophene-thiosemicarbazone compounds interact against the larger DNA groove, and corroborating the spectroscopic results, may assume an intercalating interaction mode.

CONCLUSION

Our findings highlight 5-nitro-thiophene-thiosemicarbazone derivatives, especially LNN-05, as a promising new class of compounds for further studies to provide new anticancer therapies.

Spectroscopic and viscometric determination of DNA-binding modes of some bioactive dibenzodioxins and phenazines

Push-pull dibenzodioxins and phenazines having ‘anthracene-like’ planar structures and good charge transfer character had been previously synthesised in our laboratory. The dibenzodioxins had earlier proven their anti-proliferative nature against HeLa tumor cell lines. Since phenazines are structural analogues of the former, these molecules were evaluated in course of the current study for their cytotoxic action against HeLa cell lines and they exhibited strong anti-tumor activity. This behavior could be related to their good DNA binding property. The DNA binding modes of molecules 1–4 (Fig. 1) were evaluated using various experimental techniques and they interacted with DNA in a non-covalently by both intercalative as well as groove binding mechanisms. Molecule 1 follows predominantly intercalative binding mode whereas molecules 2 and 3 have nearly equal and opposite preferences for both groove binding and intercalative modes. For molecule 4, groove binding is preferred mode of binding to DNA. A rationale for such differential binding behaviour is provided based on the subtle structural differences in our synthesised dibenzodioxins and phenazines. Elucidation of the mode of a molecule-DNA-binding event is relevant for understanding the mechanism of action of these molecules and will help promote further research into designing better DNA targeting small molecules.

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DNA binding modes of push-pull planar dibenzodioxins and phenazines were elucidated.

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DNA binding mechanistic details were obtained by spectroscopic and viscometric techniques.

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The molecular shape and geometry has a bearing on its choice of binding mode.

Selection and Identification of Novel Aptamers Specific for Clenbuterol Based on ssDNA Library Immobilized SELEX and Gold Nanoparticles Biosensor

We describe a multiple combined strategy to discover novel aptamers specific for clenbuterol (CBL). An immobilized ssDNA library was used for the selection of specific aptamers using the systematic evolution of ligands by exponential enrichment (SELEX). Progress was monitored using real-time quantitative PCR (Q-PCR), and the enriched library was sequenced by high-throughput sequencing. Candidate aptamers were picked and preliminarily identified using a gold nanoparticles (AuNPs) biosensor. Bioactive aptamers were characterized for affinity, circular dichroism (CD), specificity and sensitivity. The Q-PCR amplification curve increased and the retention rate was about 1% at the eighth round. Use of the AuNPs biosensor and CD analyses determined that six aptamers had binding activity. Affinity analysis showed that aptamer 47 had the highest affinity (Kd = 42.17 ± 8.98 nM) with no cross reactivity to CBL analogs. Indirect competitive enzyme linked aptamer assay (IC-ELAA) based on a 5′-biotin aptamer 47 indicated the limit of detection (LOD) was 0.18 ± 0.02 ng/L (n = 3), and it was used to detect pork samples with a mean recovery of 83.33–97.03%. This is the first report of a universal strategy including library fixation, Q-PCR monitoring, high-throughput sequencing, and AuNPs biosensor identification to select aptamers specific for small molecules.

Interaction of capsaicin with calf thymus DNA: A multi-spectroscopic and molecular modelling study

Studying the mode of interaction between small molecules and DNA has received much attention in recent years, as many drugs have been reported to directly interact with DNA thereby regulating the expression of many genes. Capsaicin is a capsaiciniods family phytocompound having many therapeutic applications including diabetic neuropathy, rheumatoid arthritis, prevention of DNA strand breaks and chromosomal aberrations. In this study, we have investigated the interaction of capsaicin with calf thymus DNA using a number of biophysical techniques to get an insight and better understanding of the interaction mechanism. Analysis of UV-vis absorbance spectra and fluorescence spectra indicates the formation of complex between capsaicin and Ct-DNA. Thermodynamic parameters ΔG, ΔH, and ΔS measurements were taken at different temperatures indicated that hydrogen bonding and van der Waal's forces played major role in the binding process. Additional experiments such as iodide quenching, CD spectroscopy suggested that capsaicin possibly binds to the minor groove of the Ct-DNA. These observations were further confirmed by DNA melting studies, viscosity measurements. Molecular docking provided detailed computational interaction of capsaicin with Ct-DNA which proved that capsaicin binds to Ct-DNA at minor groove. Computational molecular docking also revealed the exact sites and groups to which capsaicin interacted.