Versatile Nanocomposite Coatings with Tunable Cell Adhesion and Bactericidity

Abstract

TiO2‐Ag nanocomposites are known for their bactericidal effect during exposure to appropriate UV radiation. While involving hazardous radiation, and limited to accessible areas, the bactericidity of these coatings is not persistent in the absence of UV light, which impedes their commercial application. Herein it is shown that TiO2‐Ag nanocomposites can be made highly bactericidal without the need of irradiation. Beyond this, bactericidity can even be mitigated in the presence of pre‐irradiated coatings. Biocompatibility and cell adhesion are also negligibly small for the as‐processed, non‐irradiated coatings, and become fairly high when the coatings are irradiated prior to testing. This opens the possibility to pattern the coatings into areas with high and low cell adhesion properties. Indeed by irradiating the coating through a mechanical mask it is shown that fibroblast cell adherence is sharply confined to the irradiated area. These properties are achieved using TiO2‐Ag thin films with high silver loadings of 50 wt%. The films are processed on stainless steel substrates using solution deposition. Microstructural characterization by means of X‐ray diffraction, Raman, and X‐ray photoelectron spectroscopy, high‐resolution scanning electron microscopy, and atomic force microscopy show a highly amorphous TiO2‐AgxO nanocomposite matrix with scattered silver nanoparticles. UV irradiation of the films results in the precipitation of a high density of silver nanoparticles at the film surface. Bactericidal properties of the films are tested on α‐haemolyzing streptococci and in‐vitro biocompatibility is assessed on primary human fibroblast cultures. The results mentioned above as to the tunable bactericidity and biocompatibility of the TiO2‐Ag coatings developed herein, are amenable to silver ion release, to catalytic effects of silver nanoparticles, and to specific wettabilities of the surfaces.

Effects of Ga and Sn Additions on the Creep Strength and Oxidation Resistance of Near-α Ti Alloys

“…[26] Therefore, we concluded that deformation in the a phase is dominant in near-a Ti alloys with a small volume fraction of b phase, even though the activation energy in a-Ti is affected by solute diffusion. [36] The activation energies obtained in this study are greater than that for self-diffusion in a-Ti and are similar to the values reported for conventional alloys such as Ti-6242S and IMI 834, [27,32,33] even though the effects of Si solid solution and silicide precipitation were not factors in this study. Figure 4 shows the mass gain per unit area of the alloys oxidized in air for 340 hours at 973 K (700°C) (a) and for 240 hours at 1023 K (750°C) (b).…”

“…[27][28][29][30][31][32][33][34][35] The superior creep strength with the small volume fraction of equiaxed a phase in the present study is attributed to the concomitant effect of the following factors: (1) a larger colony size and prior b-grain size with a large volume of lamellar structure, which determines the dislocation-gliding distance; (2) possibly less grain-boundary sliding [34,35] ; and (3) an increase in the strength of the lamellar matrix in the bimodal structure as a consequence of alloy-element partitioning. [29] In the case of higher activation energies, the rate-controlling process at higher temperatures was assumed to be diffusion controlled because the activation energy for the high-temperature creep was similar to that of self-diffusion in a-Ti (e.g., 242 kJ/mol).…”

Micellar layer-by-layer synthesis of TiO2/Ag hybrid particles for bactericidal and photocatalytic activities

“…[3][4][5][6][7][8] On the other hand, silver (Ag) nanoparticles have long been known to liberate silver ions in liquids that show a broad spectrum over the antimicrobial activities. 9,10 Immobilization of Ag nanoparticles on TiO 2 to form hybrid composite particles with tailored structure and surface functionality has been demonstrated to show improved photocatalytic activity, 3,[11][12][13] as well as bactericidal activity [14][15][16] without the need of UV irradiation. * Corresponding author.…”

Creep Behavior of <I>In Situ</I> Synthesized 7715D Titanium Matrix Composite

“…1) In these activities, titanium based alloys are developed as structural materials for engine of aircraft, aerospace components, hydrogen storage materials and shape memory alloys due to their low density, high strength and modulus, corrosion resistance and other eminent properties. In spite of these advantages, applications of Ti alloys are still limited by high temperature.…”