This article describes the preparation and analysis of macroporous TiO2 films on Ti surfaces, for application in bone tissue-Ti implant interfaces. These TiO2 bioceramic films have a macroporous structure consisting of monodisperse, three-dimensional, spherical, interconnected pores adjustable in the micron size range. Micron-sized polystyrene (PS) bead templates are used to precisely define the pore size, creating macroporous TiO2 films with 0.50, 16, and 50 microm diameter pores, as shown by scanning electron microscopy. X-ray photoelectron spectroscopy shows the films to be predominantly composed of TiO2, with approximately 10% carbon. X-ray diffraction reveal rutile as the main phase when fired to the optimal temperature of 950 degrees C. Preliminary experiments find that the in vitro proliferation of human bone-derived cells (HBDC) is similar on all three pore sizes. However, higher [3H]thymidine incorporation by the HBDC is observed when they are grown on 0.50- and 16-microm pores compared to the 50-microm pores, suggesting an enhanced cell proliferation for the smaller pores.

Various surface modifications have been applied to titanium alloy (Ti-6Al-4V) implants, in an attempt to enhance osseointegration; crucial for ideal prosthetic fixation. Despite the numerous studies demonstrating that peptide-modified surfaces influence in vitro cellular behavior, there is relatively little data reporting their effects on bone remodeling. The objective of this article was to examine the effects of chemically modifying Ti-6Al-4V surfaces with a common RGD sequence, a 15-residue peptide containing GRGDSP (glycine-arginine-glycine-aspartate-serine-proline), on the modulation of bone remodeling. The expression of proteins known to be associated with osseous matrix and bone resorption were studied during the growth of human bone-derived cells (HBDC) on these peptide-modified surfaces. HBDC grown for 7 days on RGD surfaces displayed significantly increased levels of osteocalcin, and pro-collagen Ialpha1 mRNAs, compared with the production by HBDC grown on the native Ti-6Al-4V. A pattern that was also reflected at the protein levels for osteocalcin, type I collagen, and bone sialoprotein. Moreover, HBDC grown for 7 and 14 days on RGD-modified Ti-6Al-4V expressed significantly higher level of osteoclast differentiation factors and lower levels of osteoprotegerin and IL-6 proteins compared with other surfaces tested. These results suggest that different chemical treatments of implant material (Ti-6Al-4V) surface result in differential bone responses, not only their ability to form bone but also to stimulate osteoclastic formation.

The photodetachment of the O(2)(-).H(2)O cluster anion at 780 and 390 nm is investigated in comparison with O(2)(-) using photoelectron imaging spectroscopy. Despite the pronounced shift in the photoelectron spectra, the monohydration has little effect on the photoelectron angular distributions: for a given wavelength and electron kinetic energy (eKE) range, the O(2)(-).H(2)O angular distributions are quantitatively similar to those for bare O(2)(-). This observation confirms that the excess electron in O(2)(-).H(2)O retains the overall character of the 2ppi(g) HOMO of O(2)(-). The presence of H(2)O does not affect significantly the partial wave composition of the photodetached electrons at a given eKE. An exception is observed for slow electrons, where O(2)(-).H(2)O exhibits a faster rise in the photodetachment signal with increasing eKE, as compared to O(2)(-). The possible causes of this anomaly are (i) the long-range charge-dipole interaction between the departing electron and the neutral O(2).H(2)O skeleton affecting the slow-electron dynamics; and (ii) the s wave contributions to the photodetachment, which are dipole-forbidden for pi(g)(-1) transitions in O(2)(-), but formally allowed in O(2)(-).H(2)O due to lower symmetry of the cluster anion and the corresponding HOMO.

No abstract

Articles you may be interested inStudy of Nb2O y (y = 2-5) anion and neutral clusters using anion photoelectron spectroscopy and density functional theory calculations Addition of water to Al 5 O 4 − determined by anion photoelectron spectroscopy and quantum chemical calculations Contributions from two structural isomers in the photoelectron spectrum of Al 3 O 3Ϫ have been isolated using an anion beam hole-burning technique. A kite-shaped structure having a lower electron affinity than the bent rectangle isomer was partially bleached from the ion beam just prior to the photoelectron spectroscopy interaction region. Further, we have performed studies varying the time allowed for cluster formation along with density functional calculations on a feasible structural intermediate that suggest that the kite structure may actually be a precursor to the rectangle structure.

Fluorocarbon films were grown on polystyrene in vacuum from 25- to 100-eV mass-selected C3F5 + ion beams. The films were analyzed by X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray reflectivity after exposure to the atmosphere for 4−8 weeks. The X-ray reflectivity indicates films that range from ∼30 to 60-Å thick. The thinner films form at lower ion energies, where the ion penetration depth and efficiency of film formation are lowest. X-ray reflectivity estimates air−fluorocarbon film roughness values of ∼6 Å for 25- and 50-eV films but ∼20 Å for the 100-eV films. The fluorocarbon−polystyrene-buried interface displays similar roughness and trends with ion energy. The AFM roughness trends are similar, but the absolute AFM roughnesses are only ∼/4 of the X-ray reflectivity values. This discrepancy is attributed to tip effects and the method of determining roughness by AFM. The AFM images and power spectral densities of the 100-eV films displayed quasi-periodic cones spaced 300−700 Å apart. Such features are either absent or of much lower amplitude in the 25- and 50-eV films. Classical molecular dynamics simulations of C3F5 + deposition on polystyrene at energies of 50 and 100 eV/ion reveal that etching at the higher energy is largely responsible for the dissimilar film structures obtained experimentally. These results demonstrate that deposition of the fluorocarbon polyatomic ion C3F5 + allows control of film nanostructure at the surface and buried interface.

Articles you may be interested inVibrationally quantum-state-specific dynamics of the reactions of CN radicals with organic molecules in solution J. Chem. Phys. 134, 244503 (2011); 10.1063/1.3603966Addition of water and methanol to Al 3 O 3 − studied by mass spectrometry and anion photoelectron spectroscopy Study of tin-and tin cluster-cyano complexes using anion photoelectron spectroscopy and density functional calculationsThe 3.49 eV photoelectron spectra of HNiCO Ϫ , PdCO Ϫ , and PtCO Ϫ generated from the gas-phase reaction of atomic anions with methanol are presented and interpreted in the context of new density functional calculations. The calculated electron affinities ͑EAs͒ for PdCO ͑0.58 eV͒ and PtCO ͑1.13 eV͒ are in excellent agreement with experimental values ͓0.606͑10͒ and 1.212͑10͒ eV, respectively͔ while for HNiCO, the calculated EA ͑1.64 eV͒ is 0.48 eV lower than the experimental value. However, in all three cases, the vibrational frequencies and spectral profiles are consistent with calculated structures, frequencies, and normal coordinates. HNiCO Ϫ and HNiCO are predicted to be linear, with 1 ⌺ ϩ and 2 ⌬ ground states, respectively. Calculations on PdCO Ϫ agree with recent calculations by Andrews and co-workers ͓J. Phys. Chem. A 104, 3905 ͑2000͔͒ which predict a bent 2 AЈ ground state. The ground state of PtCO Ϫ is calculated to be the linear 2 ⌺ ϩ state. Both PdCO and PtCO are predicted to have 1 ⌺ ϩ ground states. For all species, backdonation of d -electron density into the CO * orbital is an important component of the metal carbonyl bond, with the effect being more pronounced in the anions.

The 4.66 eV photoelectron spectra of Al3O3−, Al3O3−⋅solvent and Al3O3−⋅(solvent)2 (solvent=H2O, D2O, and CH3OH) have been obtained and analyzed in the context of existing and preliminary new density functional theory calculations. The structures and vibrational frequencies of the two isomers of Al3O3− and Al3O3 proposed by Ghanty and Davidson [J. Phys. Chem. A 103, 8985 (1999)] agree well with structural information extracted from the Al3O3− spectra using Franck–Condon simulations. Photoelectron spectra of Al3O3−⋅solvent complexes [EA=2.5(1) eV] are broad and congested, and hydroxide formation, multiple structural isomers, and anion photodissociation are suggested as possible sources of this. The photoelectron spectra of Al3O3−⋅(solvent)2 complex spectra [EA=3.05(10) eV] show two distinct electronic transitions, several of which exhibit partially-resolved vibrational structure that are similar to the two electronic bands attributed to the bare rectangular structural isomer of Al3O3−. Possible adsorption scenarios are suggested, with hydroxide formation being the most consistent with trends observed in both the photoelectron and mass spectra.