Cytocompatibility assessment of Ti-Nb-Zr-Si thin film metallic glasses with enhanced osteoblast differentiation for biomedical applications.

Biologically safe Ti-based quaternary Ti-Nb-Zr-Si thin film metallic glass (TFMG) was fabricated by sputtering on Titanium alloy (Ti6Al4V or Ti alloy) substrates. A preliminary assessment regarding glass forming ability, thermal stability and corrosion behavior was performed. The amorphous nature of the film is evidenced from the X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) and Selected Area Electron Diffraction (SAED) patterns. Ion scattering spectroscopy (ISS) and X-ray Photoelectron Spectroscopy (XPS) were used to analyse the chemical composition of surface which indicated oxygen on the top surface of the film and confirms the presence of Ti, Nb, Si, Zr without any other impurities. The surface morphology of the film showed a smooth surface as observed from scanning electron microscope (SEM) and atomic force microscope (AFM) analysis. It is found that the TFMG can sustain in the body-fluid, exhibiting superior corrosion resistance and electrochemical stability than the bare titanium. The cytotoxicity studies with L929 fibroblast cells showed that coatings were graded as zero and non-cytotoxic in nature. No hemolysis was observed on the coated surface indicating a better hemocompatibility. Assay using SaOS-2 bone cells showed good growth on the coated surfaces. The calcium assay showed that the SaOS-2 cells grown and differentiated on the control (Tissue Culture Polystyrene) TCPS surface had the highest mineral level. Higher alkaline phosphatase activity is obtained in SaOS-2 osteoblast cell cultures on TFMG than the control.

Biomineralization of osteoblasts on DLC coated surfaces for bone implants.

Diamond like carbon (DLC) films were deposited onto Ti6Al4V and Si wafer substrates by RF plasma enhanced chemical vapor deposition. The influence of dopants such as fluorine (F), silicon (Si), and nitrogen (N) on composition, structure, and biocompatibility was investigated. Ion scattering spectroscopy analysis revealed the presence of dopant atoms in the outer-most layers of the films. Raman studies showed that the position of the G-band shifts to higher frequencies with the fluorine and nitrogen content in the DLC film, whereas the incorporation of Si into DLC induces a decrease of the position of the G peak. The corrosion behavior was studied in simulated body fluid. A higher charge transfer resistance (Rct) was observed for the doped DLC films. The indirect cytotoxicity was performed using L929 fibroblast cells. The coated surfaces were hemocompatible when tested with red blood cells. DLC films were noncytotoxic to L929 cells over a 24 h exposure. Saos-2 osteoblast cell response to the doped and undoped DLC coated surfaces was studied in adhesion, proliferation, differentiation, and mineralization assays. The production of calcium and phosphate by cells on doped DLC, particularly, nitrogen doped DLC, was higher than that on undoped DLC.

Tuning the plasmonic response of TiN nanoparticles synthesised by the transferred arc plasma technique.

Titanium nitride exhibits plasmonic behaviour in the visible and NIR region. Combined with a refractory nature, it can be an attractive alternate plasmonic material useful in many applications. Despite the plethora of methods to produce TiN nanoparticles, it remains challenging to generate high quality TiN nanoparticles efficiently. Here we demonstrate the transferred arc plasma technique as a viable way to synthesise TiN nanoparticles. We show here that modulating the processing conditions can control the optical properties and tune the plasmonic response rendering the application of TiN nanoparticles viable across many applications.

Quantifying BTEX in aqueous solutions with potentially interfering hydrocarbons using a partially selective sensor array.

Partially selective gold nanoparticle sensors have the sensitivity and selectivity to discriminate and quantify benzene, toluene, ethylbenzene, p-xylene and naphthalene (BTEXN) at concentrations relevant to the US Environmental Protection Agency. In this paper we demonstrate that gold nanoparticle chemiresistors can do so in the presence of 16 other hydrocarbons and that they did not reduce the discriminating power of the array. A two-level full factorial designed experiment was performed on unary, binary, ternary, quaternary, quinary combinations of BTEXN analytes with and without the possibly interfering hydrocarbons. The nominal component concentration of the mixtures was 100 µg L(-1), equivalent to approximately 100 parts per billion (ppb). Concentrations predicted with the random forests method had an average root mean square error of 10-20% of the component concentrations. This level of accuracy was achieved regardless of whether or not the 16 possibly interfering hydrocarbons were present. This work shows that the sensitivity and selectivity of gold nanoparticles chemiresistor sensors towards BTEXN analytes are not unduly affected by the other hydrocarbons that are expected to be present at a petroleum remediation site.

High reflectance ta-C coatings in the extreme ultraviolet.

The extreme ultraviolet (EUV) reflectance of amorphous tetrahedrally coordinated carbon films (ta-C) prepared by filtered cathodic vacuum arc was measured in the 30-188-nm range at near normal incidence. The measured reflectance of films grown with average ion energies in the ~70-140-eV range was significantly larger than the reflectance of a C film grown with average ion energy of ~20 eV and of C films deposited by sputtering or evaporation. The difference is attributed to a large proportion of sp3 atom bonding in the ta-C film. This high reflectance is obtained for films deposited onto room-temperature substrates. The reflectance of ta-C films is higher than the standard single-layer coating materials in the EUV spectral range below 130 nm. A self-consistent set of optical constants of ta-C films was obtained with the Kramers-Krönig analysis using ellipsometry measurements in the 190-950 nm range and the EUV reflectance measurements. These optical constants allowed calculating the EUV reflectance of ta-C films at grazing incidence for applications such as free electron laser mirrors.

Incorporation of Si and SiO(x) into diamond-like carbon films: impact on surface properties and osteoblast adhesion.

The interaction of human osteoblast cells with diamond-like carbon films incorporating silicon and silicon oxide (SiO(x), 1 < or = x < or = 1.5) and synthesized using the direct-current plasma-activated chemical vapour deposition method was investigated. Cell culture studies were performed for films with Si contents ranging from approximately 4 at.% to 15 at.%. Substantial differences between Si-incorporated and SiO(x)-incorporated films were found for the bonding environments of Si atoms and the hybridization of underlying carbon structures. However, osteoblast-attachment studies did not show statistically significant trends in properties of cell growth (count, area and morphology) that can be attributed either to the Si content of the films or to the chemical structure of the films. The surface energy decreased by 40% as the Si content of the SiO(x) incorporated DLC films increased to 13 at.%. The cell adhesion properties however did not change in response to lowering of the surface energy. The incorporation of both Si and SiO(x) leads to a beneficial reduction in the residual stress of the films. The average roughness of the films increases and the hardness decreases when Si and SiO(x) are added to DLC films. The impact of these changes for load-bearing biomedical applications can be determined only by carefully controlled experiments using anatomic simulators.

The influence of surface chemistry and topography on the contact guidance of MG63 osteoblast cells.

The purpose of the present study was to determine in vitro the effects of different surface topographies and chemistries of commercially pure titanium (cpTi) and diamond-like carbon (DLC) surfaces on osteoblast growth and attachment. Microgrooves (widths of 2, 4, 8 and 10 microm and a depth of 1.5-2 microm) were patterned onto silicon (Si) substrates using microlithography and reactive ion etching. The Si substrates were subsequently vapor coated with either cpTi or DLC coatings. All surfaces were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Using the MG63 Osteoblast-Like cell line, we determined cell viability, adhesion, and morphology on different substrates over a 3 day culture period. The results showed cpTi surfaces to be significantly more hydrophilic than DLC for groove sizes larger than 2 microm. Cell contact guidance was observed for all grooved samples in comparison to the unpatterned controls. The cell viability tests indicated a significantly greater cell number for 8 and 10 microm grooves on cpTi surfaces compared to other groove sizes. The cell adhesion study showed that the smaller groove sizes, as well as the unpatterned control groups, displayed better cell adhesion to the substrate.

Adherent apatite coating on titanium substrate using chemical deposition.

Plasma-sprayed "HA" coatings on commercial orthopedic and dental implants consist of mixtures of calcium phosphate phases, predominantly a crystalline calcium phosphate phase, hydroxyapatite (HA) and an amorphous calcium phosphate (ACP) with varying HA/ACP ratios. Alternatives to the plasma-spray method are being explored because of some of its disadvantages. The purpose of this study was to deposit an adherent apatite coating on titanium substrate using a two-step method. First, titanium substrates were immersed in acidic solution of calcium phosphate resulting in the deposition of a monetite (CaHPO4) coating. Second, the monetite crystals were transformed to apatite by hydrolysis in NaOH solution. Composition and morphology of the initial and final coatings were identified using X-ray diffraction (XRD), Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (EDS). The final coating was porous and the apatite crystals were agglomerated and followed the outline of the large monetite crystals. EDS revealed the presence of calcium and phosphorous elements on the titanium substrate after removing the coating using tensile or scratching tests. The average tensile bond of the coating was 5.2 MPa and cohesion failures were observed more frequently than adhesion failures. The coating adhesion measured using scratch test with a 200-microm-radius stylus was 13.1N. Images from the scratch tracks demonstrated that the coating materials were squashed without fracturing inside and/or at the border of the tracks until the failure point of the coating. In conclusion, this study showed the potential of a chemical deposition method for depositing a coating consisting of either monetite or apatite. This method has the advantage of producing a coating with homogenous composition on even implants of complex geometry or porosity. This method involves low temperatures and, therefore, can allow the incorporation of growth factors or biogenic molecules.

Solution- and solid-phase synthesis of components for tethered bilayer membranes.

The synthesis of the novel compound PhCH(2)SS(C(24)H(44)N(4)O(10))(C(20)H(41)) (5) for the preparation of tethered bilayer membranes is described. The compound is the all-amide analogue of the previously reported ester-containing membrane-forming material PhCH(2)SS(C(24)H(40)O(14))(C(20)H(41)) (1). The advanced intermediate (C(20)H(41)) C(16)H(28)N(3)O(8) (17) was prepared from the same starting materials using both solution-phase (13% yield) and solid-phase (81% yield) techniques. Monolayers on gold derived from 5 have been analyzed by ellipsometry and FTIR. The monolayers exhibit thicknesses similar to monolayers derived from 1 and possess H-bonded amide functionality.

Functional expression of chimeric receptor genes in human T cells.

Tumor immunotherapy has been limited to date by the poor antigenicity of most tumors, the immunocompromised state of many cancer patients, and the slow tumor penetration and short half-life of exogenously-introduced anti-tumor antibodies. Our group has developed a model immunotherapy system using a chimeric construct containing an antibody V region fused to a T cell activation molecule (T body) introduced by transfection into cytotoxic T cell lines, or populations of activated primary T or natural killer (NK) cells. In this study we have optimized the conditions needed for efficient transduction of human peripheral lymphocytes (PBL) using retroviral vectors pseudotyped with the gibbon ape leukemia virus (GaLV) envelope. Selection of packaging cells producing high virus titers was performed following transfection with constructs containing the green fluorescent protein (GFP), and FACS sorting. As a model chimeric receptor gene we used a tripartite construct consisting of a single-chain anti-TNP antibody variable region linked to part of the extracellular domain and the membrane spanning regions of the CD28 coreceptor molecule and joined at its 5' end to a gene fragment encoding the intracellular moiety of the gamma activation molecule common to the Fcepsilon and Fcgamma receptors. Enriched preparations of retrovectors containing this chimeric receptor and the GFP gene could stably and efficiently transduce human PBL co-activated by anti-CD3 and anti-CD28 antibodies. In routine experiments, the transgene was expressed in 35-70% of the human T cells. Such lymphocytes express the chimeric receptors on their surface and upon stimulation with hapten immobilized on plastic they can produce IL-2. Transfectomas activated in this manner also undergo specific proliferation in the absence of exogenous IL-2. Moreover, the transduced lymphocytes could effectively lyse target cells expressing the TNP hapten on their surface. These studies establish the conditions for the optimal transfection of effector lymphocytes to redirect them against a variety of tumor targets.

Optical properties and stress of ion-assisted aluminum nitride thin films.

The optical properties and stress in thin films of aluminum nitride have been studied as a function of ion energy and the ion-to-vapor arrival ratio (J(i)/J(v)) for the N(2)(+) ion-assisted deposition of aluminum. The ion energy was varied between 75 and 1000 eV. The refractive index was found to depend on the ion energy and flux. The highest index was 2.10 at 633 nm. The films were found to be highly transparent over the wavelength region 275-800 nm. The films were found to be free of major oxide contamination, and x-ray photoelectron spectroscopy studies revealed the presence of excess nitrogen in films prepared at high J(i)/J(v) values. The film stress was also found to be related to the ion energy, and an anomalously high compressive stress of -5.0 GPa was found for 100-eV N(2)(+)-assisted depositions. By comparison, films prepared by magnetron deposition were found to have lower refractive indices (1.97-1 99, n633) and higher stress (-8 to -12 GPa) when deposited in pure nitrogen.