Ioana Demetrescu

Effect of nano-topographical features of Ti/TiO2 electrode surface on cell response and electrochemical stability in artificial saliva

The paper is a new approach which aims to evaluate the relation between surface aspects (wettability and roughness) of materials based on titanium with native passive TiO(2) as untreated samples and TiO(2) nanotubes as treated discs respectively, their electrochemical stability in artificial saliva, and fibroblast cell behavior. Ti/TiO(2) modified electrodes as nanotubes with 120 nm as diameter were obtained using an electrochemical method as anodizing and surface analysis as SEM, AFM and contact angle measurements were performed to obtain topographical features and wettability. The TiO(2) nanotube structured oxide films electrochemical growth increases the stability of titanium surfaces. The electrochemical behavior of the Ti/TiO(2) nanotube surface was evaluated by corrosion parameters obtained from Tafel plots and electrical parameters for proposed circuits from electrochemical impedance spectroscopy were analyzed. The cell results indicated a slight preference in terms of cell survival and adhesion for nanostructure TiO(2) with a more hydrophilic character and the electrochemical data revealed that such features are connected with better stability in artificial saliva. The roughness seems to be not conclusive for this case.

Reduced inflammatory activity of RAW 264.7 macrophages on titania nanotube modified Ti surface.

Macrophages play a pivotal role in the hosts response to biomaterials being considered as an essential cell type during both optimal tissue-implant integration and pathologic process of implant failure. Hence, understanding of their cellular activity on biomaterials is important for improving evaluation and design of biomaterials for biomedical applications. In the present study, we have comparatively investigated the interactions of titania nanotubes (78 nm diameter) and commercial pure Ti with RAW 264.7 macrophages in both standard and pro-inflammatory (stimulation with lipopolysaccharide, LPS) culture conditions. In vitro tests showed that TiO2 nanotubes exhibited significantly decreased inflammatory activity of macrophages with respect to cytokine and chemokine gene expression/protein secretion, induction of foreign body giant cells (FBGCs) and nitric oxide (NO) release thereby mitigating the inflammatory response induced by LPS as compared to flat Ti surface. Therefore, our results suggest a novel role of TiO2 nanotubes in modulating macrophage response in biomaterial-associated bacterial infections. Overall, the current study provides new insight into how TiO2 nanotubes can be involved in macrophage activation and supports the great promise of such surface modifications for biomedical applications.

The two step nanotube formation on TiZr as scaffolds for cell growth

Various TiO2 nanotubes on Ti50Zr alloy have been fabricated via a two step anodization method in glycol with 15vol.% H2O and 0.2M NH4F under anodization controlled voltages of 15, 30 and 45V. A new sonication treatment in deionized water with three steps and total sonication time as 1min was performed after the first anodization step in order to remove the oxide layer grown during 2h. The second step of anodization was for 1h and took place at the same conditions. The role of removed layer as a nano-prepatterned surface was evidenced in the formation of highly ordered nanotubular structures and morphological features were analyzed by SEM, AFM and surface wettability. The voltage-controlled anodization leads to various nanoarhitectures, with diameters in between 20 and 80nm. As biological assay, cell culture tests with MG63 cell line originally derived from a human osteosarcoma were performed. A correlation between nanostructure morphological properties as a result of voltage-controlled anodization and cell response was established.

Antimicrobial activity of the surface coatings on TiAlZr implant biomaterial

This study is devoted to antimicrobial activity of new surface coatings on TiAlZr. Ti alloys such as TiAlZr are used as implant biomaterials, but, despite the good behavior of such alloys in simulated conditions, bacterial infections appear after the introduction of an implant into the body. The infections are typically caused by the adherence and colonization of bacteria on the surfaces of the implants. The study presents preparation and surface morphology characterization of coatings obtained via anodizing, as well as biomimetic coatings with hydroxyapatite and silver ions with and without antibiotic. The percentage inhibition of Escherichia coli bacteria growth was evaluated for each of the studied coating, and a Trojan-horse model of silver nanoparticles (nAg) antibacterial activity at interface was proposed. Such coatings could be more important taking into account that antibacterial treatments with antibiotics are becoming less effective due to their intensive use.

Nanochannels formed on TiZr alloy improve biological response

UNLABELLED In the present work we report the fabrication of non-thickness-limited 1D nanostructures with nanochannelar structure by anodization of Ti50Zr alloy in hot glycerol-phosphate electrolyte. These nanochannelar structures show high and adjustable aspect ratios and provide as-formed already partial crystallinity for nanochannels. In vitro studies were performed to assess the inflammatory response to nanochannel coated surfaces using RAW 264.7 macrophages. The results show that these nanochannels yield a reduced amount of metabolically-active macrophages, low potential to induce macrophage fusion into FBGC, and low concentration of pro-inflammatory cytokines in the culture medium. Moreover, higher hydrophilicity and lower corrosion rates were registered, compared to compact oxide. Collectively, the results indicate a more favorable cellular response on such nanoscale topography as compared to compact oxide control substrate, and suggest that surface architecture design of nanochannel type on implant materials holds promise for biomedical applications. STATEMENT OF SIGNIFICANCE The use of titanium and its alloys in biomedical devices has been extensively investigated, especially for alloys possessing inherent antibacterial properties such as TiZr alloys. We report for the first time the growth of mesoporous structures, aligned oxide nanochannels, on Ti50Zr alloy. The advantages of these nanochannelar surfaces are a high surface area, a long range ordered nanoscale topology and already partial crystallinity in the as-grown state. In vitro studies performed on RAW 264.7 macrophages demonstrate the potential of nanochannels to lower the inflammatory response, thus reducing the foreign body reaction against Ti50Zr biomedical implants and promoting the successful integration of the implant.

Effect of anodization on the surface characteristics and electrochemical behaviour of zirconium in artificial saliva

The paper is focused on elaboration of ZrO2 films on pure zirconium via anodizing in phosphoric acid with and without fluoride at constant potentials of 30 V and 60 V. The structure and composition of the films were investigated using scanning electronic microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The composition of the oxides formed at both potentials can be identified as monoclinic ZrO2. In addition to Zr and O, the layers formed in phosphoric acid contain phosphorus originating from the phosphoric acid. When the phosphoric acid solution contains NaF, fluorine is also incorporated into the oxide layer. The oxides formed at a higher voltage have greater roughness than those formed at 30 V. Anodized samples exhibit smaller current densities during anodic polarization compared to the as-received zirconium covered with native oxide.

Passive and Bioactive Films on Implant Materials and their Efficiency in Regenerative Medicine

The article presents various behavior aspects of passive and bioactive films on Ti and CoCr alloy and their efficiency in regenerative medicine, taking into account that metallic materials are typically inert, but various surface treatments are devoted to build films which change them into active materials. The studied passive films were oxides and bioactive films with collagen and phosphate coatings. All films were characterized from the point of view of their electrochemical stability. Their composition was evaluated using infrared spectroscopy and electronic microscopy type SEM with and EDAX module The cytotoxicity test for fibroblast growth using direct contact method was the in vitro biocompatibility evaluation for all studied films.

Improving Natural Biopolymeric Membranes Based on Chitosan and Collagen for Biomedical Applications Introducing Silver

The aim of this study was to obtain new films based on collagen-chitosan with and without silver for biomedical applications. Membranes with a thin transparent elastic structure were obtained and after immersion in silver nitrate new membranes with silver have been elaborated and their physicochemical properties were assessed using infrared spectroscopy as well as contact angle determinations, and sorption properties. The water absorption has permitted the evaluation of the diffusion coefficient for modified collagen membranes and the values were comparable with diffusion coefficient specific for human cornea. Adsorption and desorption studies of silver ions were investigated based on the concentration of the silver solution. This concentration was determined by an inductively coupled plasma spectrometer. Antimicrobial investigations performed on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria and hemolytic properties assays have been evaluated measuring optical density. The enhancement of antibacterial activity of membranes with silver content was emphasized.

Present and Future Trends in TiO2 Nanotubes Elaboration, Characterization and Potential Applications

The paper is focused on TiO2 nanotubes elaboration, characterization and potential applications, starting from the idea that monitoring anodizing conditions is a way to obtain nanotubes with various dimensions and various potential applications related to the change of hydrophilic – hydrophobic balance, biocompatibility, nano-porosity, stability, etc. Such properties are important for the use of Ti as biomaterial, as self–cleaning, solar energy conversion, controllable wettability, photocatalysis, etc. The electrochemical behaviour of the nanotubes was monitoring by Tafel plots and open circuit potential determinations, and was discussed in connection with surface features evaluated from scanning electron microscopy, atomic force microscopy and contact angle measurements.

In vitro hemocompatibility and corrosion behavior of new Zr-binary alloys in whole human blood

AbstractThe aim of this study is to evaluate the accuracy of three binary alloys’ composition, and their biocompatibility. Depending on the intended use of the medical devices made from these materials, dynamic or static tests should be performed. We have chosen static tests as we thought they may be used as knee or hip replacement, and not as cardiac valves.Three binary alloys ( Zr10Nb, Zr2.5Nb and Zr12Ta) were obtained from high purity powders (>99.9%), using an induction furnace first, and an electric arc furnace for a perfect homogenization. Their final composition was verified with a XRF analyzer-INNOV-X.Hemolysis tests can determine the degree of red blood cells lysis and the release of hemoglobin. The released hemoglobin quantity was extremely small, under 2%, in all cases, and the coagulation tests showed no risk for thrombosis. The electrochemical behavior was also studied in biological fluid, human female serum, and showed a low corrosion rate.The obtained alloys do not cause hemolysis, so they are hemocompatible with all blood types.