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

Abstract

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. Concealed activity: A series of titanocene-functionalized silica-based materials have been synthesized, characterized, and studied in vitro against human cell lines (see figure). They act as Trojan horses for the incorporation of the titanium active species into cells, leading to much higher quantities of titanium uptake in cells, changing the dynamics of apoptotic morphological and functional changes, and inducing programmed cell death in tumor cell populations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.