Temperature programmed desorption was used to study the reaction of CH3OH on several different ceria-based model catalysts. These catalysts consisted of a CeO2(111) single crystal and thin ceria films supported on α-Al2O3(0001) and yttria-stabilized zirconia (100). The results of this study demonstrate that the reaction of CH3OH on CeO2 surfaces is highly structure sensitive and depends on crystallographic orientation, the concentration of surface oxygen vacancies, and the oxidation state of surface cerium cations. The primary decomposition pathway for methoxide intermediates adsorbed on surface oxygen vacancy sites is dehydrogenation to produce H2CO and surface hydroxyl groups. The surface hydroxyl groups then either react with additional methoxides to reform CH3OH or react to produce H2O. In contrast, methoxides adsorbed on partially reduced ceria surfaces, possibly on Ce3+ sites, undergo complete dehydrogenation to CO and H2.

The clinical use of metallic expandable intravascular stents has resulted in improved therapeutic outcomes for coronary artery disease. However, arterial reobstruction after stenting, in-stent restenosis, remains an important problem. Gene therapy to treat in-stent restenosis by using gene vector delivery from the metallic stent surfaces has never been demonstrated. The present studies investigated the hypothesis that metal-bisphosphonate binding can enable site-specific gene vector delivery from metal surfaces. Polyallylamine bisphosphonate (PAA-BP) was synthesized by using Michael addition methodology. Exposure to aqueous solutions of PAA-BP resulted in the formation of a monomolecular bisphosphonate layer on metal alloy surfaces (steel, nitinol, and cobaltchromium), as demonstrated by x-ray photoelectron spectroscopy. Surface-bound PAA-BP enabled adenoviral (Ad) tethering due to covalent thiol-binding of either anti-Ad antibody or a recombinant Ad-receptor protein, D1. In arterial smooth muscle cell cultures, alloy samples configured with surface-tethered Ad were demonstrated to achieve site-specific transduction with a reporter gene, (GFP). Rat carotid stent angioplasties using metal stents exposed to aqueous PAA-BP and derivatized with anti-knob antibody or D1 resulted in extensive localized Ad-GFP expression in the arterial wall. In a separate study with a model therapeutic vector, Adinducible nitric oxide synthase (iNOS) attached to the bisphosphonate-treated metal stent surface via D1, significant inhibition of restenosis was demonstrated (neointimal͞media ratio 1.68 ؎ 0.27 and 3.4 ؎ 0.35; Ad-iNOS vs. control, P < 0.01). It is concluded that effective gene vector delivery from metallic stent surfaces can be achieved by using this approach.gene therapy ͉ local delivery ͉ restenosis T he use of balloon expandable metallic stents has resulted in improved therapeutic outcomes for coronary artery disease (1). However, stent angioplasty is complicated in many patients by reobstruction due to the formation of a neointima in the stented arterial segment, a disease process known as in-stent restenosis (2). The mechanisms responsible for instent restenosis involve proliferation and migration of medial smooth muscle cells (SMCs) and an associated increase in extracellular matrix components (2). The use of polymercoated drug-eluting stents has markedly decreased the incidence of in-stent restenosis observed with unmodified metal stents (3). However, both experimental (4) and clinical (5) studies indicate a number of concerns about this approach, because polymer coatings on stents cause a more pronounced inf lammatory response than metal surfaces (6), thus delaying rather than preventing restenosis (7,8).Polymer-coated gene-delivery stents have been demonstrated in animal studies to be effective for both reporter (9-13) and therapeutic (14, 15) vector delivery. Nevertheless, their use is problematic because of harmful properties of the polymer coatings (6, 7). Therefore, the present experiments investigated gene deli...

The reaction of methanol on TiO 2 (110)-supported vanadium oxide was studied using temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). TPD results show that methanol is oxidized to formaldehyde on monolayer and submonolayer vanadia films on TiO 2 (110), whereas both clean TiO 2 (110) and multilayer vanadia films supported on TiO 2 (110) are relatively inactive for this reaction. HREELS results demonstrate that methoxides are the primary surface intermediates in the oxidation of methanol to formaldehyde on the supported vanadium layers. The reactivity trends obtained for the model catalysts used in this study are similar to those observed for high surface area analogues. This suggests that vanadia films supported on single-crystal metal oxide substrates are excellent model systems for studying the relationships between the structure and reactivity of supported oxide catalysts.

The growth, and reactivity of monolayer V 2 O 5 films supported on TiO 2 (110) produced via the oxidation of vapor-deposited vanadium were studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Oxidation of vapor-deposited vanadium in 10 -7 Torr of O 2 at 600 K produced vanadia films that contained primarily V +3 , while oxidation in 10 -3 Torr at 400 K produced films that contained primarily V +5 . The reactivity of the supported vanadia layers for the oxidation of methanol to formaldehyde was studied using TPD. The activity for this reaction was found to be a function of the oxidation state of the vanadium cations in the film. AbstractThe growth, and reactivity of monolayer V 2 O 5 films supported on TiO 2 (110) produced via the oxidation of vapor-deposited vanadium were studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD).Oxidation of vapor-deposited vanadium in 10 -7 Torr of O 2 at 600 K produced vanadia films that contained primarily V +3 , while oxidation in 10 -3 Torr at 400 K produced films that contained primarily V +5 . The reactivity of the supported vanadia layers for the oxidation of methanol to formaldehyde was studied using TPD. The activity for this reaction was found to be a function of the oxidation state of the vanadium cations in the film.