Exploring DNA binding ability of two novel α-N-heterocyclic thiosemicarbazone palladium(II) complexes

Polyvalent aptamer DNA nanoassembly based near-infrared carbon dots and rolling circle amplification for synergistic therapy of breast cancer

Integrating imaging and therapy is of great significance in the field of tumor treatment. Here, we report a polyvalent aptamer nanoplatform for breast cancer cell treatment based on rolling circle amplification (RCA). The platform consists of a long single-stranded DNA scaffold from RCA and short-stranded DNAs with various functions. One short strand is linked to near-infrared carbon dots (NIR-CDs), another carries a MUC1 aptamer targeting cancer cells, and the third loads small interfering RNA (siRNA) for gene therapy. Doxorubicin (Dox) attaches to the platform via CG base pairs, integrating fluorescence targeting, photothermal therapy (PTT), gene therapy, and chemotherapy. Aptamer enhances breast cancer cell uptake of the platform. NIR-CDs serve as fluorescence imaging agents and are used for PTT. When deoxyribonucleases degrade the nanoplatform, Dox is released and then exerts its chemotherapeutic effect. SiRNA can form the RNA-induced silencing complex to reduce drug tolerance and enhance the efficacy of loaded drugs. The experimental results show that the platform can accumulate in cancer cells, exert a killing effect on them, and meanwhile reduce side effects on normal cells. In summary, this study expands the application of DNA materials in biomedicine by constructing a diagnostic and therapeutic platform that integrates NIR-CDs and RCA.

Antiproliferative activity in breast cancer cells of PtL2: A steroid-thiosemicarbazone platinum(II) complex

Breast cancer remains one of the most diagnosed cancers in women worldwide. Metallodrugs such as cisplatin are used in advanced stages and hormone independent tumors. We hereby report the synthesis and characterization of a new benzaldehyde thiosemicarbazone functionalized with an estradiol derivative, LH, and two metal complexes, PdCl2(LH) and PtL2. Both complexes were studied in solution showing enough stability to further perform antitumoral activity studies. The Pd(II) complex was discarded for its poor performance while PtL₂ exhibited similar cytotoxic activity to cisplatin (CDDP) in estrogen receptor (+) and triple-negative breast cancer cells. Moreover, PtL₂ demonstrated reduced toxicity in healthy cell lines. It induced cell cycle arrest at the G0/G1 phase, distinguishing its mechanism of action from CDDP, which predominantly blocks cells in the S phase. Additionally, PtL₂ displayed a balanced intracellular distribution between the nucleus and cytoplasm, independent of estrogen receptor status. Further analysis revealed that PtL₂ dysregulated antioxidant enzyme expression, potentially disrupting redox homeostasis. These findings highlight PtL₂'s potential as a promising alternative to conventional platinum-based therapies, warranting further investigation into its molecular mechanisms and therapeutic applications.

Synthesis, structural characterisation, and anticancer potential of mono and dinuclear Pd(II) complexes of N-(2-pyridyl)thiourea

Cancer is a prominent global cause of mortality. Palladium complexes have the potential to serve as effective anticancer and pharmacological agents, offering a viable alternative to platinum medications. This work focused on the development of a new thiolato-bridged dinuclear [Pd(M3MPyThU)Cl]2 and mononuclear palladium [Pd(M3MPyThU)2] complexes containing 1-methyl-3-(3-methylpyridin-2-yl) thiourea (HM3MPyThU) ligand. The prepared ligand and complexes have been fully characterised by various spectroscopic and single-crystal crystallographic data. The ligand and complexes were further examined for their anticancer activities against the HT-29 (human colon) and MCF-7 (human breast) cancer cells along with the standard drug cisplatin, and the outcome suggests that tested compounds have a better cytotoxic response against HT-29 cells. The order of anticancer activity was found as [Pd(M3MPyThU)Cl]2 > cisplatin > [Pd(M3MPyThU)2] > HM3MPyThU. The complex [Pd(M3MPyThU)Cl]2 demonstrated potent cytotoxic effects against HT-29 cells with an IC50 value of 10 ± 3.3 μM. The comparison of the anticancer activity of the described complexes with previous reports on HT-29 cells suggests that the described complexes have better anticancer activity than previously reported complexes. Further assays were performed for [Pd(M3MPyThU)Cl]2 to gain insights into the mechanism of cell death and found that reduced mitochondrial membrane potential and increased ROS production, highlighting mitochondrial-dependent apoptosis as the major mechanism for tumour cell death. Additionally, [Pd(M3MPyThU)Cl]2 was found to be more selective compared to cisplatin since it exhibited decreased toxicity towards healthy cells (HEK-293).

A select thiosemicarbazone copper(II) complex induces apoptosis in gastric cancer and targets cancer stem cells reducing pluripotency markers

Copper(II)-based complexes are promising candidates as anti-cancer agents due to their ability to target cancer cells. Here we describe the synthesis and characterization of two copper(II) thiosemicarbazone complexes with the ligands 4-(dimethylamino)benzaldehyde N4-methylthiosemicarbazone (HL1) and 4-(dimethylamino)benzaldehyde N4-(4-(dimethylamino)phenylthiosemicarbazone (HL2) and general formula [Cu(L)2]. The complexes show stability in aqueous solution with 1 % of DMSO that allows to stablish its solution profile in biological buffers. Compound [Cu(L1)₂] lipophilicity was lower than [Cu(L2)₂], however, its solubility in biological buffer was not only better but also its DLS and ζ-potential data. In vitro studies demonstrate a higher cytotoxic effect of [Cu(L1)₂] on gastric cancer cells. The proposed mechanism of action consists in the generation of free radicals that induce DNA lesions, oxidative stress and ultimately autophagy deregulation and apoptosis. Additionally, [Cu(L1)₂] is equally active on gastric cancer stem cells and tumor cells resistant to cisplatin. More importantly, stem cells treated with [Cu(L1)₂] show a downregulation of pluripotency markers such as TWIST, NANOG and OCT4. Overall, our results with [Cu(L1)₂] prompt a significant advancement in the development of rational-designed pharmaceuticals for combating cancer.

Bioactive Thiosemicarbazone Coordination Metal Complexes: Synthesis, Characterization, Theoretical analysis, Biological Activity, Molecular Docking and ADME analysis

Mn(II) and Cu(II) complexes having the formula [M(L)2 ]X2 of ligand, i. e., 2-acetyl-5-methylfuranthiosemicarbazone were synthesized. Various analytical and spectroscopic techniques described the structure of synthesized complexes. Molar conductance confirmed the electrolytic nature of the complexes. The theoretical study of the complexes explained the structural property and reactivity. The chemical reactivity, interaction and stability of the ligand and metal complexes were studied with the help of global reactivity descriptors. MEP analysis was used to investigate the charge transfer in the ligand. The biological potency was evaluated against two bacteria and two fungi. Complexes demonstrated superior inhibitory action to ligand. The inhibitory effect was also checked at the atomic scale using molecular docking, which confirmed the experimental results. Cu(II) complex was shown to have the most inhibitory effect in experimental and theoretical studies. To check the bioavailability and drug-likeness, ADME analysis was also done.

Visible-light driven regioselective synthesis, characterization and binding studies of 2-aroyl-3-methyl-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidines with DNA and BSA using biophysical and computational techniques

In recent times, fused azaheterocycles emerged as impressive therapeutic agents. Binding studies of such azaheterocycles with biomolecules is an important subject for pharmaceutical and biochemical studies aiming at the design and development of new drugs. Fused heterocyclic scaffolds, such as thiazolopyrmidines have long been used in the pharmaceutical industry for the treatment of various diseases. In this study, we have accomplished a regioselective synthesis of 2-aroyl-3-methyl-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidines by the reaction of tetrahydropyrimidine-2(H)-thione with α-bromo-1,3-diketones, generated in situ from 1,3-diketones and NBS, using visible light as an inexpensive, green and renewable energy source under mild reaction conditions with wide-ranging substrate scope. The regioisomer was characterized unambiguously by 2D-NMR [1H-13C] HMBC and [1H-13C] HMQC spectroscopy. In silico toxicity data analysis showed the low toxicity risks of the synthesized compounds. Computational molecular docking studies were carried out to examine the interaction of thiazolo[3,2-a]pyrimidines with calf-thymus DNA (ct-DNA) and Bovine Serum Albumin (BSA). Moreover, different spectroscopic approaches viz. steady-state fluorescence, competitive displacement assay, UV-visible and circular dichroism (CD) along with viscosity measurements were employed to investigate the binding mechanisms of thiazolo[3,2-a]pyrimidines with DNA and BSA. The results thus obtained revealed that thiazolo[3,2-a]pyrimidines offer groove bindings with DNA and showed moderate bindings with BSA.

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.

Chemical and Biological Evaluation of Thiosemicarbazone-Bearing Heterocyclic Metal Complexes

Thiosemicarbazones (TSCNs) constitute a broad family of compounds (R₁R₂C=N-NH-C(S)- NR₃R₄), particularly attractive because many of them display some biological activity against a wide range of microorganisms and cancer cells. Their activity can be related to their electronic and structural properties, which offer a rich set of donor atoms for metal coordination and a high electronic delocalization providing different binding modes for biomolecules. Heterocycles such as pyrrole, imidazole and triazole are present in biological molecules such as Vitamine B12 and amino acids and could potentially target multiple biological processes. Considering this, we have explored the chemistry and biological properties of thiosemicarbazones series and their complexes bearing heterocycles such as pyrrole, imidazole, thiazole and triazole. We focus at the chemistry and cytotoxicity of those derivatives to find out the structure activity relationships, and particularly we analyzed those examples with the TSCN units in which the mechanism of action information has been profoundly studied and pathways determined, to promote future studies for heterocycle derivatives.

Ni, Pd, and Pt complexes of a tetradentate dianionic thiosemicarbazone-based O^N^N^S ligand

New tetradentate phenolate O^N^N^S thiosemicarbazone (TSC) ligands and their Ni(ii), Pd(ii) and Pt(ii) complexes were studied. The diamagnetic and square planar configured orange or red complexes show reversible reductive electrochemistry and in part reversible oxidative electrochemistry at very moderate potentials. DFT calculations show essentially pyridyl-imine centred lowest unoccupied molecular orbitals (LUMO) while the highest occupied molecular orbitals (HOMO) receive contributions from the phenolate moiety, the metal d orbitals and the TSC thiolate atom in keeping with UV-vis spectroelectrochemistry. DFT calculations in conjunction with IR spectra showed details of the molecular structures, the UV-vis absorptions were modelled through TD-DFT calculation with very high accuracy. UPS is fully consistent with UV-vis absorption and TD-DFT calculated data and shows decreasing HOMO-LUMO gaps along the series Pd > Pt > Ni.

Palladium (II) complexes with thione and thioalkylated thiosemicarbazones: Electrochemical, antimicrobial and thermogravimetric investigations

Four methoxy substitute salicylidene thiosemicarbazones were synthesized. The reaction of both thione and thioalkylated thiosemicarbazones with PdCl₂ in ethanol yields ONS-coordinated chelate complexes with general formula [Pd(L)Cl]. The structures of eight compounds were characterized by using analytical and spectroscopic methods. Electrochemistry of the Pd(II) complexes was studied using cyclic voltammetric technique. The CVs of the complexes were quite complicate because of some oxidative responses of the ligands which proceed by forming conjugated -N=CH-, -HC=CH- and -N=CH-HC=CH- groups. Two cathodic responses attributed to one electron reduction of Pd(II)/(I) and Pd(I)/(0) were observed for the central ion coordinated with S atom of H₃C-S- group whereas only one reduction peak appeared when the Pd(II) coordinated with S atom of >C=S group of thiosemicarbazone ligand. The latter also showed an additional anodic response assigned to Pd(II)/(III) oxidation. Thermogravimetric analysis (TGA) technique was used to investigate and compare the thermal properties of the ligands and their metal complexes. In vitro antimicrobial activity of thiosemicarbazones and their complexes was evaluated against four Gram-negative bacteria, three Gram-positive bacteria, and antifungal activity against three fungi.

Evaluation of biomolecular interactions and cytotoxic activity of organometallic binuclear Ru(II) complexes of ferrocenyl thiosemicarbazones

Four new ferrocenyl substituted thiosemicarbazone ligands (L1-L4) and their corresponding binuclear ruthenium(II) arene complexes of the general type [(η⁶-p cym)(L)Ru(μ-im)Ru(L)(η⁶-p-cym)]Cl (C1-C4) and [(η⁶-p cym)(L)Ru(μ-azpy)Ru(L)(η⁶-p-cym)]Cl₂ (C5-C8) (cym = cymene, im = imidazole, azpy = 4,4'-azopyridine) have been synthesized and characterized. The structures of the complexes were established through DFT calculations and geometry optimization. The interactions of the binuclear complexes with DNA were investigated by absorption, emission and viscosity studies which indicated that the complexes bind to DNA via intercalation. Meanwhile, the interaction of complexes with the protein, bovine serum albumin (BSA), has also been studied using fluorescence emission spectroscopy. The experimental results show that the binuclear complexes exhibit good binding propensities to BSA. The complexes can quench the intrinsic fluorescence of BSA remarkably through a static or dynamic quenching process. In addition, the in vitro cytotoxicity of complexes C1-C8 against HeLa cell line was assayed which showed lower IC₅₀ values indicating their higher cytotoxicity and potency in killing the cancer cells at low concentrations.Communicated by Ramaswamy H. Sarma.