An organized hydrophobic monolayer is formed on smooth zero-valent gold by adsorption of octadecyltrichlorosilane (OTS) from a hexadecane solution. Wetting properties, infrared (IR) spectra, and ellipsometry measurements are consistent with the silyl moiety adjacent to the metal surface and with an all-trans conformation hydrocarbon chain extended vertically from the surface with a small average tilt. The silyl head groups appear to be incorporated into a two-dimensional cross-linked network of Si-O-Si bonds within the monolayer. However, polymerization is not complete as suggested by IR and Auger spectra which indicate the presence of SiOH groups and residual Cl, respectively. Electrochemical measurements indicate the monolayer-covered gold surface behaves as a blocked electrode containing pinhole defects. Conditions for film formation on Pt were also investigated for comparison.

The in vitro and in vivo performance of hydroxyapatite (HAp) coatings can be modified by the addition of different trace ions, such as silicon (Si), lithium (Li), magnesium (Mg), zinc (Zn) or strontium (Sr) into the HAp lattice, to more closely mirror the complex chemistry of human bone. To date, most of the work in the literature has considered single ion-substituted materials and coatings, with limited reports on co-substituted calcium phosphate systems. The aim of this study was to investigate the potential of radio frequency magnetron sputtering to deposit Sr and Zn co-substituted HAp coatings using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The FTIR and XPS results highlight that all of the Sr, Zn and Sr-Zn co-substituted surfaces produced are all dehydroxylated and are calcium deficient. All of the coatings contained HPO groups, however; only the pure HAp coating and the Sr substituted HAp coating contained additional CO groups. The XRD results highlight that none of the coatings produced in this study contain any other impurity CaP phases, showing peaks corresponding to that of ICDD file #01-072-1243 for HAp, albeit shifted to lower 2θ values due to the incorporation of Sr into the HAp lattice for Ca (in the Sr and Sr-Zn co-substituted surfaces only). Therefore, the results here clearly show that RF magnetron sputtering offers a simple means to deliver Sr and Zn co-substituted HAp coatings with enhanced surface properties. (a) XRD patterns for RF magnetron sputter deposited hydroxyapatite coatings and (b)-(d) for Sr, Zn and Sr-Zn co-substituted coatings, respectively. The XPS spectra in (b) confirms the presence of a HA sputter deposited coating as opposed to

Polyetheretherketone (PEEK) has emerged as the material of choice for spinal fusion devices, replacing conventional materials such as titanium and its alloys due to its ability to easily overcome a lot of the limitations of traditional metallic biomaterials. However, one of the major drawbacks of this material is that it is not osteoinductive, nor osteoconductive, preventing direct bone apposition. One way to overcome this is through the modification of the PEEK with bioactive calcium phosphate (CaP) materials, such as hydroxyapatite (HA–Ca10(PO4)6(OH)2). RF magnetron sputtering has been shown to be a particularly useful technique for the deposition of CaP coatings due to the ability of the technique to provide greater control of the coating’s properties. The work undertaken here involved the deposition of HA directly onto PEEK via RF magnetron at a range of deposition times between 10–600 min to provide more bioactive surfaces. The surfaces produced have been extensively characterised using X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), stylus profilometry, and Time of Flight Secondary Ion Mass Spectrometry (ToFSIMS). XPS results indicated that both Ca and P had successfully deposited onto the surface, albeit with low Ca/P ratios of around 0.85. ToFSIMS analysis indicated that Ca and P had been homogeneously deposited across all the surfaces. The SEM results showed that the CaP surfaces produced were a porous micro-/nano-structured lattice network and that the deposition rate influenced the pore area, pore diameter and number of pores. Depth profiling, using ToFSIMS, highlighted that Ca and P were embedded into the PEEK matrix up to a depth of around 1.21 µm and that the interface between the CaP surface and PEEK substrate was an intermixed layer. In summary, the results highlighted that RF magnetron sputtering can deliver homogenous CaP lattice-like surfaces onto PEEK in a direct, one-step process, without the need for any interlayers, and provides a basis for enhancing the potential bioactivity of PEEK.

No abstract

Bioactive materials offer particular clinical benefits in the field of dental implantology, where differentiation of stem cells towards an osteoblastic lineage is required for osseointegration and appropriate function of implants in vivo. The aim of this study was to evaluate the osteoblastic response of Stro‐1 +ve periodontal ligament stem cells (PDLSCs) to three well‐characterized biomaterial surfaces: an abraded titanium surface (cpTi) control; a polycrystalline titanium surface, with both micro and nanotopography produced by radio frequency magnetron sputtering (TiTi); and the same surface incorporating a sputter deposited calcium phosphate coating (CaP‐TiTi). The CaP‐TiTi surfaces were nonstoichiometric, carbonated, and calcium rich with a Ca/P ratio of 1.74. PDLSCs were grown on each surface in the absence of supplementary osteogneic‐inducing agents. Osteoblastic responses were assessed for up to 21 days in culture by measuring gene expression using real time q‐PCR and via assessment of intracellular alkaline phosphatase (ALP) activity. Gene expression analysis for the CaP‐TiTi surfaces showed a significant late stage up‐regulation of Secreted Phosphoprotein 1. Additionally, there was a significant up‐regulation of the Wnt signaling genes β‐catenin and Wnt Family Member 5 A on days 14 and 21, respectively for the CaP‐TiTi surface. A significant increase in intracellular ALP at day 21 for the CaP‐TiTi surface was also observed. These data suggest that the CaP‐TiTi surfaces provide the bioactive conditions required for direct osteoblastic differentiation of PDLSCs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1692–1702, 2017.