Nuclease and anticancer activity of antioxidant conjugated terpyridine metal complexes

Copper-assisted anticancer activity of hydroxycinnamic acid terpyridine conjugates on triple-negative breast cancer

The development of active therapeutic agents to treat highly metastatic cancer while minimizing damage to healthy cells is of utmost importance. Due to potential antioxidant properties, hydroxycinnamic acid derivatives (caffeic acid and p-coumaric acids) were found to inhibit highly metastatic breast cancer cell growth both in vitro and in vivo without much effect on normal cells. Especially due to the structure-activity relationships, ester and amide derivatives of hydroxycinnamic acids are reported to gain much higher radical scavenging ability than their naked hydroxycinnamic acid analogs like caffeic acid and p-coumaric acid. These results prompted us to design a set of ligands by incorporating an amide moiety on caffeic acid and p-coumaric acid to achieve the least toxicity towards healthy cell lines. Further, the Cu(II) complexes of amide-coupled caffeic acid and p-coumaric acid ligands have been explored for their therapeutic activity on triple-negative breast cancer and other cancer cells like colon, and prostate cancer. The Cu(II) complexes (4 & 5) were characterized by UV-Vis spectroscopy, FTIR, and X-band EPR spectroscopy. The trigonal bipyramidal geometry of complexes was confirmed by the X-band EPR spectra recorded in solution state at liquid N2 temperature. The purity of the complexes was determined by elemental analysis and HPLC traces. Initially, Calf thymus DNA (ct-DNA) binding studies with the complexes were explored. The results suggested the complexes (4 & 5) bind majorly through an intercalative mode of binding with ct-DNA, whereas no significant binding was observed for the bare organic ligands (2 & 3). The intercalation binding modes of 4 and 5 were further supported by UV-visible spectroscopy, ct-DNA melting point analysis, and CD spectroscopy. Moreover, these complexes showed better activity towards cisplatin-resistant TNBC cell lines (4T1, a TNBC cell line derived from the mammary gland tissue of a mouse). The combination of antioxidants and Cu(II) as the metal center made the complexes more cytotoxic toward cancer cell lines (4T1) (IC50 ∼ 3.5 ± 2.5 μM) and the least toxic toward healthy cells (L929) (IC50 ∼ 15 ± 5 μM). Finally, the mechanism of cell death was studied using JC-1 staining and a cell colony formation assay. These studies might help in designing safer anticancer drugs for treating more aggressive types of cancer.

Optimization of Antiproliferative Properties of Triimine Copper(II) Complexes

Cu(II) complexes with 2,2':6',2″-terpyridines (terpy) and 2,6-bis(thiazol-2-yl)pyridines (dtpy) with 1- or 2-naphtyl and methoxy-naphtyl were synthesized to elucidate the impact of the triimine core, naphtyl linking mode, and presence of methoxy groups on the antiproliferative activity of [CuCl2(Ln)]. Their antiproliferative effect was analyzed in ovarian (A2780) and colorectal (HCT116) carcinomas and colorectal carcinoma resistant to doxorubicin (HCT116-DoxR) cell lines and in normal human fibroblasts. Among all complexes, the 1- and 2-naphtyl substituted terpy Cu(II) complexes (Cu1a and Cu1b) showed the strongest cytotoxicity, namely, in HCT116-DoxR 2Dcells and were also capable of inducing the loss of cell viability in 3D HCT116-DoxR spheroids. Their intracellular localization, capability to increase reactive oxygen species (ROS), and interaction with DNA (nonintercalative mode) trigger oxidative DNA cleavage leading to cell death by apoptosis and autophagy. Cu1a and Cu1b do not show in vivo toxicity in a chicken embryo and can interact with bovine serum albumin (BSA).

Glutathione - IR 797 coupled Casein Nano-Trojan for augmenting the therapeutic efficacy of camptothecin in highly invasive triple negative breast cancer

The rapid metastasis & heterogenic constitution of triple negative breast cancer (TNBC) limits drug entry to the tumor, reducing treatment effectiveness. To address this, we have synthesized Casein nanoparticles (Cn NPs) with attached glutathione (GSH), a natural ligand for cancer cell overexpressed γ-glutamyl transpeptidase (GGT). Cn NPs encapsulated with Camptothecin and NIR dye IR 797 (CCN NPs) for combinatorial therapy of TNBC. The GSH-CCN nanoparticles (CCNG NPs) act as a Nano-Trojan to deceive the cancer cells by delivering therapeutic payloads directly to specific target cells. In this study, Casein Nano-Trojan is equipped with GSH as a targeting ligand for GGT. The binding of CCNG NPs with cell surface receptors switched the anionic charge to catanionic, prompting the target cell to engulf the nanoparticles. The Casein Nano-Trojan releases its therapeutic payload inside the target cell, potentially inhibiting proliferation & inducing a high percentage of cell death (85 ± 7 %). Disintegration of mitochondrial membrane potential, inhibition of both migration & re-growth were observed. Immunofluorescence, acridine orange/ethidium bromide stain, and nuclear fragmentation assay further confirmed the substantial DNA damage induced by the high expression of γH2AX and p53. Significant therapeutic efficacy was observed in the 3D spheroids of 4T1 cells and in vivo breast cancer mice model (BALB/c). These findings demonstrate that CCNG NPs could be an effective treatment approach for highly metastatic triple negative breast cancer.

In vitro and in vivo antitumor activities of Ru and Cu complexes with terpyridine derivatives as ligands

Six terpyridine ligands(L1-L6) with chlorophenol or bromophenol moiety were obtained to prepare metal terpyridine derivatives complexes: [Ru(L1)(DMSO)Cl2] (1), [Ru(L2)(DMSO)Cl2] (2), [Ru(L3)(DMSO)Cl2] (3), [Cu(L4)Br2]·DMSO (4), Cu(L5)Br2 (5), and [Cu(L6)Br2]⋅CH3OH (6). The complexes were fully characterized. Ru complexes 1-3 showed low cytotoxicity against the tested cell lines. Cu complexes 4-6 exhibited higher cytotoxicity against several tested cancer cell lines compared to their ligands and cisplatin, and lower toxicity towards normal human cells. Copper(II) complexes 4-6 arrested T-24 cell cycle in G1 phase. The mechanism studies indicated that complexes 4-6 accumulated in mitochondria of T-24 cells and caused significant reduction of the mitochondrial membrane potential, increase of the intracellular ROS levels and the release of Ca2+, and the activation of the Caspase cascade, finally inducing apoptosis. Animal studies showed that complex 6 obviously inhibited the tumor growth in a mouse xenograft model bearing T-24 tumor cells without significant toxicity.

Antioxidant conjugated metal complexes and their medicinal applications

Antioxidants are naturally available and man-made substances have the ability to protect cells from damage due to a number of intracellular redox activities. Moreover, Antioxidants such as α-lipoic acid, curcumin and catechin are good anticancer agents. In recent years, the usage of metal complexes as therapeutic agents is gaining importance due to their useful biological properties. Most of the metal ions act as the essential components in building drug molecules that serve as medicines for cancer and neurodegenerative diseases. In particular, metals like copper, gold, ruthenium, and platinum have adequate anticancer properties at both micro- and nano-levels. Hence, conjugation of antioxidants with metals and metal-based compounds results in hybrid bioactive materials with improved anticancer properties. In this chapter, medicinal applications of antioxidant conjugated metal complexes are reviewed and discussed.

Oxidative DNA cleavage mediated by a new unexpected [Pd(BAPP)][PdCl4] complex (BAPP = 1,4-bis(3-aminopropyl)piperazine): crystal structure, DNA binding and cytotoxic behavior

A novel Pd(ii) double complex, [Pd(BAPP)][PdCl4], containing the 1,4-bis(3-aminopropyl)piperazine (BAPP) ligand is investigated. X-ray crystallography of a single crystal confirmed the structure of the [Pd(BAPP)][PdCl4] complex. The spectroscopic behavior was also elucidated using elemental analysis, nuclear magnetic resonance and Fourier-transform infrared spectroscopy, and mass spectrometry. The antimicrobial susceptibility of the [Pd(BAPP)][PdCl4] complex against all tested microbial strains was lower than that of the BAPP ligand except for C. albicans. The cytotoxic impacts of the BAPP ligand and its [Pd(BAPP)][PdCl4] complex were evaluated in vitro for HepG2, CaCo-2 and MCF7 cell lines as well as the WI-38 normal cell line. The anticancer activity was markedly improved by the complexation. The [Pd(BAPP)][PdCl4] complex could selectively inhibit the tested cancer cells in a safe way to the non-tumorigenic cell (WI-38). From the DNA binding studies with ultraviolet-visible spectrophotometry, the [Pd(BAPP)][PdCl4] complex interacts more efficiently with the calf thymus DNA than its BAPP ligand through the intercalative binding mode. In the absence of an external reductant, the [Pd(BAPP)][PdCl4] complex cleaved the intact supercoiled pBR322 DNA under physiological conditions in a concentration-dependent manner. Additionally, electrophoretic experiments were performed in the presence of different radical scavengers, namely DMSO, NaN3 and KI, and ruled out the hydrolytic mechanistic pathway of the reaction and suggested that the oxidative mechanism is the preferred one. The results of the binding affinity of the [Pd(BAPP)][PdCl4] complex to human DNA were modeled using a molecular docking study showing that the complex interacts more strongly with human DNA than the ligand. Finally, an in vitro pharmacokinetic study was assessed through in silico ADME predictions.

Copper in tumors and the use of copper-based compounds in cancer treatment

Copper homeostasis is strictly regulated by protein transporters and chaperones, to allow its correct distribution and avoid uncontrolled redox reactions. Several studies address copper as involved in cancer development and spreading (epithelial to mesenchymal transition, angiogenesis). However, being endogenous and displaying a tremendous potential to generate free radicals, copper is a perfect candidate, once opportunely complexed, to be used as a drug in cancer therapy with low adverse effects. Copper ions can be modulated by the organic counterpart, after complexed to their metalcore, either in redox potential or geometry and consequently reactivity. During the last four decades, many copper complexes were studied regarding their reactivity toward cancer cells, and many of them could be a drug choice for phase II and III in cancer therapy. Also, there is promising evidence of using ⁶⁴Cu in nanoparticles as radiopharmaceuticals for both positron emission tomography (PET) imaging and treatment of hypoxic tumors. However, few compounds have gone beyond testing in animal models, and none of them got the status of a drug for cancer chemotherapy. The main challenge is their solubility in physiological buffers and their different and non-predictable mechanism of action. Moreover, it is difficult to rationalize a structure-based activity for drug design and delivery. In this review, we describe the role of copper in cancer, the effects of copper-complexes on tumor cell death mechanisms, and point to the new copper complexes applicable as drugs, suggesting that they may represent at least one component of a multi-action combination in cancer therapy.

An in vitro selective inhibitory effect of silver(i) aminoacidates against bacteria and intestinal cell lines and elucidation of the mechanism of action by means of DNA binding properties, DNA cleavage and cell cycle arrest

Novel silver(i) aminoacidate complexes {[Ag(HVal)(H2O)(NO3)]}n (AgVal) and {[Ag3(HAsp)2(NO3)]}n·nH2O (AgAsp) were prepared, investigated and fully characterized by vibrational spectroscopy (mid-IR), elemental analysis, thermogravimetric analysis, X-ray crystallography and mass spectrometry. Their stability in D2O and PBS buffer was verified by time-dependent 1H and 13C NMR measurements. Their in vitro antibacterial activity (against pathogenic Staphylococcus aureus CCM4223, Escherichia coli CCM4787) and that against probiotic bacteria Lactobacillus plantarum CCM7102 and Lactobacillus reuteri (L26) were determined and potential dosing concentration was evaluated. The cytotoxicity of both the complexes against intestinal porcine epithelial (IPEC-1) and human epithelial colorectal adenocarcinoma (CaCo-2) cell lines was determined using the colorimetric MTT assay and against human metastatic melanoma (A2058), human pancreatic adenocarcinoma (PaTu 8902), human cervical adenocarcinoma (HeLa), human colorectal carcinoma (HCT116), human leukaemic T cell lymphoma (Jurkat), and human dermal fibroblasts (HDF) using colorimetric MTS assay. The selectivity index (SI) was identified for intestinal cancer (CaCo-2) and healthy (IPEC-1) cells. The mechanism of action of AgVal and AgAsp was further elucidated and discussed by the study of their binding affinity toward the CT DNA, the ability to cleave the supercoiled form of pUC19 DNA and the ability to influence numbers of cells within each cell cycle.

Synthesis, X-ray structure, antiproliferative activity, interaction with HSA and docking studies of three novel mono and binuclear copper complexes containing the maltol ligand

The present study aims at synthesizing three new copper(ii) complexes of maltol in the presence of 1,10-phenanthroline-, 2,2′-bipyridine- and 4,4-dibromo-2,2′-bipyridine ligands.