Naphthyl-substituted titanocene dichloride complexes: Synthesis, characterization and in vitro studies

Hydrolytically Stable TiIV-Hydrazone-Based Metallodrugs: Protein Interaction and Anticancer Potential

In this work, three titanium(IV) [TiIV(L1-3)2] (1-3) complexes have been reported using three different tridentate dibasic ONO donor hydrazone ligands, pyridine-4-carboxylic acid (3-ethoxy-2-hydroxybenzylidene)-hydrazide (H2L1), furan-2-carboxylic acid (3-ethoxy-2-hydroxybenzylidene)-hydrazide (H2L2), and thiophene-2-carboxylic acid (3-ethoxy-2-hydroxybenzylidene)-hydrazide (H2L3) tethered with heterocyclic moieties. Elemental analysis, FT-IR, UV-vis, NMR, HR-ESI-MS, and single-crystal X-ray analysis have been used to characterize H2L1-3 and 1-3. In solid structures of 1-3, two ligand molecules with N2O4 donor sets give distorted octahedral geometries to the metal center. The aqueous stability of 1-3 was investigated and well correlated to their perceived pharmacological results. During the investigation, all three complexes were found to be hydrolytically stable in a 90% DMSO-d6/10% D2O (v/v) medium up to 48 h. Furthermore, the interaction of 1-3 with bovine serum albumin (BSA) was tested using fluorescence and absorption techniques. The complexes showed static quenching with a biomolecular quenching constant of Kq ∼ 1013 proposing a high affinity of complexes for BSA. Finally, the anticancer potential of 1-3 was tested against HeLa, A549, and NIH-3T3 cell lines. Among all, 1 with an IC50 value of 11.6 ± 1.1 μM against HeLa cells was found to be the most cytotoxic in the series. Furthermore, it has been found that the compounds induce an apoptotic mode of cell death, which is confirmed by the live cell confocal microscopy and flow cytometry techniques.

Modulation of the mechanism of apoptosis in cancer cell lines by treatment with silica-based nanostructured materials functionalized with different metallodrugs

The mesoporous silica-based material SBA-15 (Santa Barbara Amorphous-15) has been modified with the aminodiol ligand 3-[bis(2-hydroxyethyl)amino]propyltriethoxysilane (PADOH) to give the corresponding material SBA-PADOH. Subsequent functionalization with a diorganotin(iv) compound, SnPh2Cl2 (1), and with two titanocene derivatives, TiCp2Cl2 ([Ti(η5-C5H5)2Cl2] (2)) and TiCpCpPhNfCl2 ([Ti(η5-C5H5)(η5-C5H4CHPhNf)Cl2] (3) (Ph = C6H5; Nf = C10H7)), gave the materials SBA-PADO-SnPh2 (M1), SBA-PADO-TiCp2 (M2) and SBA-PADO-TiCpCp* (M3), respectively. SBA-PADOH and M1-M3 have been characterized by various techniques such as FT-IR, XRD, XRF, solid-state NMR, nitrogen adsorption-desorption isotherms, electrochemical methods, SEM and TEM, observing that the functionalization has mainly taken place inside the pores of the corresponding porous system. In addition, mechanistic aspects of the apoptosis triggered by the synthesized materials have been studied in vitro in tumour cell lines derived from three distinct types of cancer in order to elucidate their growth inhibition and interference with the expression of tumour necrosis factor alfa (TNF-α) and the first apoptosis signal receptor (Fas or tumour necrosis factor receptor 6). It was observed that the antiproliferative and proapoptotic capacity of the materials depends on their functionalization with the different cytotoxic prodrugs (organotin or titanocene derivatives). The study shows that M1-M3 influence the metabolic activity of the tumour cells and modulate the apoptotic pathways by different mechanisms, according to the active compound inside the material.

Anti-cancer applications of titanocene-functionalised nanostructured systems: an insight into cell death mechanisms

A series of alkenyl-substituted titanocene compounds have been supported on the mesoporous silica-based material KIT-6. The corresponding functionalised materials were completely characterised by different techniques (solid-state multinuclear NMR spectroscopy, IR spectroscopy, N2 adsorption-desorption isotherms, X-ray fluorescence and diffraction, SEM and TEM) to observe the incorporation of the titanocene derivatives on the external surface of the material KIT-6. Both the titanocene compounds and the materials were tested in vitro against a wide variety of human cancer and normal cell lines. A very high cytotoxicity of the synthesised titanocene derivatives (IC50 values in the range of those described in the literature for the most active cytotoxic titanocene compounds), with selectivity towards cancer cell lines was observed. The cytotoxic activity of the materials is the highest reported to date for titanocene-functionalised materials. In addition, higher Ti uptake (from 4 to 23% of the initial amount of Ti) of the cells treated with materials was observed with respect to those treated with "free" titanocene derivatives (which gave Ti uptake values from 0.4 to 4.6% of the initial amount of Ti). Additional experiments with the titanocene derivatives and the functionalised materials revealed that changes to the morphological and functional dynamics of apoptosis occurred when the active titanocene species were incorporated into mesoporous materials. In addition, the materials could induce programmed cell death in tumour cell populations by impairing the damaged DNA repair mechanisms and by upregulation of intrinsic and extrinsic apoptotic signalling pathways.