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As the debate about TiO2 food additive safety is still open, the present study focuses on the extraction and characterisation of TiO2 (nano)particles added as a whitening agent to confectionary products, that is, chewing gum pellets. The aim was to (1) determine the colloidal properties of suspensions mutually containing TiO2 and all other chewing gum ingredients in biologically relevant media (preingestion conditions); (2) characterise the TiO2 (nano)particles extracted from the chewing gum coating (after ingestion); and (3) verify their potential photocatalysis. The particle size distribution, in agreement with the zeta potential results, indicated that a small but significant portion of the particle population retained mean dimensions close to the nanosize range, even in conditions of moderate stability, and in presence of all other ingredients. The dispersibility was enhanced by proteins (i.e., albumin), which acted as surfactants and reduced particle size. The particle extraction methods involved conventional techniques and no harmful chemicals. The presence of TiO2 particles embedded in the sugar-based coating was confirmed, including 17–30% fraction in the nanorange (2 layer surrounding the TiO2 particles.

Even though Ti-based implants are the most used materials for hard tissue replacement, they may present lack of osseointegration on the long term, due to their inertness. Hydrothermal treatment (HT) is a useful technique for the synthesis of firmly attached, highly crystalline coatings made of anatase titanium dioxide (TiO2), providing favorable nanoroughness and higher exposed surface area, as well as greater hydrophilicity, compared to the native amorphous oxide on pristine titanium. The hydrophilicity drops even more by photofunctionalization of the nanostructured TiO2-anatase coatings under UV light. Human mesenchymal stem cells exhibited a good response to the combination of the positive surface characteristics, especially in respect to the UVB pre-irradiation. The results showed that the cells were not harmed in terms of viability; even more, they were encouraged to differentiate in osteoblasts and to become osteogenically active, as confirmed by the calcium ion uptake and the formation of well-mineralized, bone-like nodule structures. In addition, the enrichment of hydroxyl groups on the HT-surfaces by UVB photofunctionalization accelerated the cell differentiation process and greatly improved the osteogenesis in comparison with the nonirradiated samples. The optimal surface characteristics of the HT-anatase coatings as well as the high potentiality of the photo-induced hydrophilicity, which was reached during a relatively short pre-irradiation time (5 h) with UVB light, can be correlated with better osseointegration ability in vivo; among the samples, the superior biological behavior of the roughest and most hydrophilic HT coating makes it a good candidate for further studies and applications.

Metallic materials have attracted the interest from a wide research community including materials scientists, materials engineers, biologists and medical doctors for their use in the biomedical area. Some alloy compositions are already in use in the market but suffer from several shortcomings. For this reason, novel, optimized, non-toxic, biocompatible compositions are being continuously devised. This chapter first reviews and discusses the advantages of bulk metallic glasses (BMGs) for orthopaedic applications, with special emphasis on their mechanical properties. Examples of newly developed permanent Ti-based and biodegradable Mg-based materials are given. In the second part of this chapter, the surface engineering methods currently available to modify the surface of Ti alloys are discussed. The outermost material layer in contact with the surrounding tissue acts as the biointerface and, hence, if appropriately designed, it can provide enhanced mechanical and corrosion resistance to the bioimplant and prevent from ions leaching. Finally, the recent progress on the formation of nanostructured titania coatings by hydrothermal treatment on the surface of Ti-based alloys is analysed.

Cancer theranostic is an approach that combines cancer diagnostic and therapeutic capabilities into a single agent. We synthesized Gadolinium-doped mesoporous TiO2 microbeads (TiO2 + xGd MBs; x = 0%, 5%, and 10%), which can be used as a contrast agent in magnetic resonance imaging and as a photosensitizer in photodynamic therapy. Human osteosarcoma MG-63 cells were used as an in vitro model for cancer cells. In preliminary experiments, we studied the cytotoxicity of TiO2 + xGd MBs with different Gd contents (0%, 5%, and 10%). To study cellular internalization of different TiO2 + xGd MBs, differential interference microscopy and transmission electron microscopy were performed. Phototoxicity of Gd-doped TiO2 MBs (TiO2 + 5%Gd and TiO2 + 10%Gd MBs) was evaluated and compared with undoped TiO2 MBs to determine if Gd-doping can be used to design TiO2 MBs for theranostic medicinal purposes. The viability of MG-63 cells exposed to TiO2 + xGd MBs and UV-A radiation was examined by resazurin assay, neutral red uptake assay, and differential staining using propidium iodide and Hoechst 33342. All the tested TiO2 + xGd MBs were internalized by MG-63 cells and significantly reduced cell viability after 3 min UV-A radiation, while the viability of untreated cells was unaffected by 3 min radiation. Moreover, our results show that MG-63 cells internalize TiO2 + 5%Gd MBs and TiO2 + 10%Gd MBs to a much greater extent than undoped TiO2 MBs, which resulted in higher phototoxicity of Gd-doped TiO2 MBs. These outcomes suggest that Gd-doped TiO2 MBs have a potential use in theranostic medicine.

The paper reports on the photoinduced properties of hydrothermally treated (HT) titanium used for bone implants. The anatase coatings composed of 30–100 nm anatase crystals exhibited high photocatalytic activity and good photo-induced wettability, reaching a superhydrophilic state, despite the larger crystal dimensions than the previously reported optimal ones. These properties are due to a suitable combination of surface texture, roughness, thickness, crystal morphology and particle size, which allowed the two independent photo-induced phenomena to occur simultaneously. The results on caffeine degradation by photocatalysis and the prolonged effect (up to two weeks) of photo-induced wettability in dark suggested a possible applicability of the HT anatase coatings as bacteria-repelling surfaces for body implants, in favor of a better osseointegration in vivo.

Copyright © Materials Research Society 2016. The glass-forming Ti75Zr10Si15 and Ti60Zr10Nb15Si15 alloys composed of nontoxic elements may represent new materials for biomedical applications. For this study, melt-spun alloy samples exhibiting glass-matrix nanocomposite structures were subjected to thermal oxidation treatments in synthetic air to improve their surface characteristics. 550 °C was identified as the most appropriate temperature to carry out oxidative surface modifications while preserving the initial metastable microstructure. The modified surfaces were evaluated considering morphological and structural aspects, and it was found that the oxide films formed at 550 °C are amorphous and consist mainly of TiO2; their thicknesses were estimated to be ∼560 nm for Ti75Zr10Si15 and ∼460 nm for Ti60Zr10Nb15Si15. The thermally treated sample surfaces exhibit not only higher roughnesses and higher hardnesses but also improved wettability compared to the as-spun materials. By immersion of oxidized samples in simulated body fluid Ca- and P-containing coatings exhibiting typical morphologies of apatite are formed. ispartof: JOURNAL OF MATERIALS RESEARCH vol:31 issue:9 pages:1264-1274 status: published

In this study, the physicochemical properties of several commercial ultrafine TiO2 powders and their behaviour in the as-received form and colloidal suspensions were analysed. Besides the particle size, the morphology and agglomeration state of the dry powders, dispersibility, ζ-potential and sedimentation in water and in phosphate-buffered saline (PBS) were studied. Also, leaching of ions from the powders during ageing in physiological solution and the ability of the photoactivated powders to decompose organic substances were evaluated. The examined TiO2 powders revealed diversified characteristics when dispersed in water. In general, while in dry conditions the particle size appeared in the nano-range (down to 32 nm), the particles were agglomerated in aqueous suspensions at pH ~7 and only a minor amount showed dimensions below 200 nm, but none below 100 nm. The inherent pH of the 3 % suspensions varies from 3.7 to 7.5 and the surface charge at these pH values varied from highly positive to highly negative values. In PBS, the surface charge is negative and relatively low for all the samples, which resulted in agglomeration. Five out of six powders exhibited significant photocatalytic activity when exposed to UV irradiation. This also includes one cosmetic-grade powder. Furthermore, during the immersion in aqueous media at physiological temperature, the powders released foreign ions, which might also contribute to the results of cytotoxicity tests. The results revealed the major role of the particle surface charge and its impact on particle dispersion or agglomeration. Due to the high ionic strength in the liquids relevant for cell-surface interaction tests, for all the examined titania powders the nanoparticulate character was lost. However, the presence of impurities and photocatalysis might further contribute to the results of cytotoxicity tests.

It is known that the "race for the surface" determining the in vivo response is strictly connected to the physico-chemical properties of the material, especially at its surface. Accordingly, the study of surface roughness, charge and wettability is fundamental to predict the bio-response to the implant. In this work, streaming potential was chosen as a reliable method to quantify the solid surface charge of hydrothermally treated (HT) TiO2-anatase nano-crystalline coatings, grown on titanium substrates. The influence of metal and ionic conductance on the zeta potential values was taken into account, allowing for the correlation of the surface charge with the coating porosity, the semiconductor character of the TiO2 nano-crystals and the metallic nature of the bulk titanium.

Biomedical implants made of titanium-based materials are expected to have certain essential features including high bone-to-implant contact and optimum osteointegration, which are often influenced by the surface topography and physicochemical properties of titanium surfaces. The surface structure in the nanoscale regime is presumed to alter/facilitate the protein binding, cell adhesion and proliferation, thereby reducing post-operative complications with increased lifespan of biomedical implants. The novelty of our TiO2 nanostructures lies mainly in the high level control over their morphology and roughness by mere compositional change and optimisation of the experimental parameters. The present work focuses on the wetting behaviour of various nanostructured titanium surfaces towards water. Kinetics of contact area of water droplet on macroscopically flat, nanoporous and nanotubular titanium surface topologies was monitored under similar evaporation conditions. The contact area of the water droplet on hydrophobic titanium planar surface (foil) was found to decrease during evaporation, whereas the contact area of the droplet on hydrophobic nanorough titanium surfaces practically remained unaffected until the complete evaporation. This demonstrates that the surface morphology and roughness at the nanoscale level substantially affect the titanium dioxide surface–water droplet interaction, opposing to previous observations for microscale structured surfaces. The difference in surface topographic nanofeatures of nanostructured titanium surfaces could be correlated not only with the time-dependency of the contact area, but also with time-dependency of the contact angle and electrochemical properties of these surfaces.

This study reports on the selective adsorption of whole plasma proteins on hydrothermally (HT) grown TiO2-anatase coatings and its dependence on the three main surface properties: surface charge, wettability and roughness. The influence of the photo-activation of TiO2 by UV irradiation was also evaluated. Even though the protein adhesion onto Ti-based substrates was only moderate, better adsorption of any protein (at pH = 7.4) occurred for the most negatively charged and hydrophobic substrate (Ti non-treated) and for the most nanorough and hydrophilic surface (HT Ti3), indicating that the mutual action of the surface characteristics is responsible for the attraction and adhesion of the proteins. The HT coatings showed a higher adsorption of certain proteins (albumin 'passivation' layer, apolipoproteins, vitamin D-binding protein, ceruloplasmin, α-2-HS-glycoprotein) and higher ratios of albumin to fibrinogen and albumin to immunoglobulin γ-chains. The UV pre-irradiation affected the surface properties and strongly reduced the adsorption of the proteins. These results provide in-depth knowledge about the characterization of nanocrystalline TiO2 coatings for body implants and provide a basis for future studies on the hemocompatibility and biocompatibility of such surfaces.

The electrochemical behavior of polycrystalline TiO2 anatase coatings prepared by a one-step hydrothermal synthesis on commercially pure (CP) Ti grade 2 and a Ti13Nb13Zr alloy for bone implants was investigated in Hank’s solution at 37.5 °C. The aim was to verify to what extent the in-situ-grown anatase improved the behavior of the substrate in comparison to the bare substrates. Tafel-plot extrapolations from the potentiodynamic curves revealed a substantial improvement in the corrosion potentials for the anatase coatings. Moreover, the coatings grown on titanium also exhibited lower corrosion-current densities, indicating a longer survival of the implant. The results were explained by considering the effects of crystal morphology, coating thickness and porosity. Evidence for the existing porosity was obtained from corrosion and nano-indentation tests. The overall results indicated that the hydrothermally prepared anatase coatings, with the appropriate morphology and surface properties, have attractive prospects for use in medical devices, since better corrosion protection of the implant can be expected.

Surface charge is one of the most significant properties for the characterisation of a biomaterial, being a key parameter in the interaction of the body implant with the surrounding living tissues. The present study concerns the systematic assessment of the surface charge of electrochemically anodized TiO2 nanotubular surfaces, proposed as coating material for Ti body implants. Biologically relevant electrolytes (NaCl, PBS, cell medium) were chosen to simulate the physiological conditions. The measurements were accomplished as titration curves at low electrolytic concentration (10(-3) M) and as single points at fixed pH but at various electrolytic concentrations (up to 0.1 M). The results showed that all the surfaces were negatively charged at physiological pH. However, the zeta potential values were dependent on the electrolytic conditions (electrolyte ion concentration, multivalence of the electrolyte ions, etc.) and on the surface characteristics (nanotubes top diameter, average porosity, exposed surface area, wettability, affinity to specific ions, etc.). Accordingly, various explanations were proposed to support the different experimental data among the surfaces. Theoretical model of electric double layer which takes into account the asymmetric finite size of ions in electrolyte and orientational ordering of water dipoles was modified according to our specific system in order to interpret the experimental data. Experimental results were in agreement with the theoretical predictions. Overall, our results contribute to enrich the state-of-art on the characterisation of nanostructured implant surfaces at the bio-interface, especially in case of topographically porous and rough surfaces.