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Microtubules are hollow protein cylinders of 25 nm diameter which are implicated in cytokinetics and proliferation in all eukaryotic cells. Here we demonstrate in vivo how multiwalled carbon nanotubes (MWCNTs) interact with microtubules in human cancer cells (HeLa) blocking mitosis and leading to cell death by apoptosis. Our data suggest that, inside the cells, MWCNTs display microtubule biomimetic properties, assisting and enhancing noncentrosomal microtubule polymerization and stabilization. These features might be useful for developing a revolutionary generation of chemotherapeutic agents based on nanomaterials.

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The interplay between the Jahn-Teller (JT) effect and octahedron tilting in transition-metal perovskites is investigated as a function of pressure. Our focus is on its effects on the exchange and electron-phonon interactions, both having a strong influence on materials properties. We demonstrate that the JT distortion in Cu 2+ and Mn 3+ is reduced upon compression and is eventually suppressed at pressures above 20 GPa. X-ray diffraction and x-ray absorption measurements in A 2 CuCl 4 layer perovskites (A: Rb, C n H 2n+1 NH 3 ; n = 1-3) show that, although pressure slightly reduces the long Cu-Cl distance in comparison to the Cu-Cu distance in the layer, the JT distortion is stable in the 0-20 GPa range. The difference between lattice (β C 0 = 0.14 GPa −1 ) and local CuCl 6 (β 0 = 0.016 GPa −1 ) compressibilities, together with the high stability of the JT distortion, lead to CuCl 6 tilts upon compression. The evolution of the elongated CuCl 6 octahedron in A 2 CuCl 4 , as well as MnF 6 in CsMnF 4 and MnO 6 in LaMnO 3 and DyMnO 3 , toward a nearly regular octahedron takes place above 20 GPa, in agreement with experimental results and a model analysis based on the JT energy derived from optical absorption spectroscopy: E JT = 0.25-0.45 eV/Cu 2+ , E JT = 0.45 eV/Mn 3+ (CsMnF 4 ), and E JT = 0.25 eV/Mn 3+ (LaMnO 3 ). The proposed model clarifies controversial results about pressure-induced JT quenching in Cu 2+ and Mn 3+ systems, providing an efficient complementary means to predict pressure behavior in perovskites containing JT transition-metal ions.

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