Titanium dioxide based nanomaterials for photocatalytic water treatment

Water treatment using photocatalysis has gained extensive attention in recent years. Photocatalysis is promising technology from green chemistry point of view. The most widely studied and used photocatalyst for decomposition of pollutants in water under ultraviolet irradiation is TiO2 because it is not toxic, relatively cheap and highly active in various reactions. Within this thesis unmodified and modified TiO2 materials (powders and thin films) were prepared. Physico-chemical properties of photocatalytic materials were characterized with UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), ellipsometry, time-of-flight secondary ion mass spectrometry (ToF-SIMS), Raman spectroscopy, goniometry, diffuse reflectance measurements, thermogravimetric analysis (TGA) and nitrogen adsorption/desorption. Photocatalytic activity of prepared samples in aqueous environment was tested using model compounds such as phenol, formic acid and metazachlor. Also purification of real pulp and paper wastewater effluent was studied. Concentration of chosen pollutants was measured with high pressure liquid chromatography (HPLC). Mineralization and oxidation of organic contaminants were monitored with total organic carbon (TOC) and chemical oxygen demand (COD) analysis. Titanium dioxide powders prepared via sol-gel method and doped with dysprosium and praseodymium were photocatalytically active for decomposition of metazachlor. The highest degradation rate of metazachlor was observed when Pr-TiO2 treated at 450ºC (8h) was used. The photocatalytic LED-based treatment of wastewater effluent from plywood mill using commercially available TiO2 was demonstrated to be promising post-treatment method (72% of COD and 60% of TOC was decreased after 60 min of irradiation). The TiO2 coatings prepared by atomic layer deposition technique on aluminium foam were photocatalytically active for degradation of formic and phenol, however suppression of activity was observed. Photocatalytic activity of TiO2/SiO2 films doped with gold bipyramid-like nanoparticles was about two times higher than reference, which was not the case when gold nanospheres were used.

Integrin traffic and signalling – from plasma membrane to endosomes

Integrins are the main cell surface receptors by which cells adhere to the surrounding extracellular matrix (ECM). Cells regulate integrin-mediated adhesions by integrin endo/exocytic trafficking or by altering the integrin activation status. Integrin binding to ECM-components induces several intracellular signalling cascades, which regulate almost every aspect of cell behaviour from cell motility to survival, and dysregulation of integrin traffic or signalling is associated with cancer progression. Upon detachment, normal cells undergo a specialised form of programmed cell death namely anoikis and the ECM-integrin -mediated activation of focal adhesion kinase (FAK) signalling at the cell surface has been considered critical for anoikis suppression. Integrins are also constantly endocytosed and recycled back to the plasma membrane, and so far the role of integrin traffic in cancer has been linked to increased adhesion site turnover and cell migration. However, different growth factor receptors are known to signal also from endosomes, but the ability of integrins to signal from endosomes has not been previously studied. In this thesis, I demonstrate for the first time that integrins are signalling also from endosomes. In contrast to previous believes, integrin-induced focal adhesion kinase (FAK) signalling occurs also on endosomes, and the endosomal FAK signalling is critical for anoikis suppression and for cancer related processes such as anchorage-independent growth and metastasis. Moreover, we have set up a new integrin trafficking assay and demonstrate for the first time in a comprehensive manner that active and inactive integrins undergo distinct trafficking routes. Together these results open up new horizons in our understanding of integrins and highlight the fundamental connection between integrin traffic and signalling.