Abstract Dental implants are especially susceptible to bacterial adhesion and so microbial contamination. Several techniques have been explored in order to obtain implant surfaces enriched with silver (Ag). The main challenge is to obtain a bactericidal effect keeping the surface biocompatible. In this regard plasma-assisted deposition is a very attractive technique due to its versatility and low environmental impact. Thus, the present work aimed at evaluating the chemical stability, antibacterial activity, and biocompatibility of a commercially pure titanium (cp-Ti) surface containing very low amounts of plasma-deposited Ag. Ag deposition obtained by 10 minutes sputtering was able to promote antibacterial action (around 30%) on a clearly cytocompatible Ti/Ag surface with no apparent impact on biocompatibility. Taken together these results indicate that the proposed deposition process has a great potential for dental implant application with the advantage of using very small amounts of silver to achieve efficacy.

Abstract It’s proposed a single methodology for the encapsulation of Aloe vera oil or microalgae fatty acids using the complex coacervation process between gelatin and gum arabic. Although a very recurrent method, it is not trivial to establish a single coacervation methodology to encapsulate different compounds. The optimal synthesis conditions, that resulted in the best yield and encapsulation efficiency, are 1:1 (m/m) wall-to-core ratio, a temperature of 40°C and agitation speed of 10,000 rpm. Optical microscopy analysis revealed that the microcapsules are spherical, have average diameters of 112 μm (A. vera) and 118 μm (microalgae) and do not form agglomerates. The microcapsules were characterized by the osmotic pressure at which they ruptured, allowing the calculation of their mechanical resistance, which resulted in 392 MPa (A. vera) and 425 MPa (microalgae). The presented optimized methodology to encapsulate both compounds aims to contribute to their efficient and rational use, especially in cosmeceutical applications.

The aim of this work was to study the corrosion process of new aluminium alloy AA2524-T3 (Solution Heat Treated and Cold Worked), which is a promising substitute of the base line AA2024-T3 for aircrafts fabrication, by global and localised techniques in sodium chloride medium (0.05 mol L-1 NaCl). The open circuit potential results revealed a stochastic evolution of pitting events and to the resulting variations in the ratio of passive/active areas and/or cathode/anode, which may be related to the presence of different types of intermetallics. The cyclicvoltammetry showed that the corrosion potential (Ecorr) and the pit nucleation potential (E pit) values are quite similar (approximately -0.525 V). The results of EIS show that the corrosion rate is quite stable, with no tendency to increase or decrease for longer immersion periods. The results of SVET were in agreement with the results obtained by EIS technique, showing strong anodic activity on the surface with no repassivation along the whole immersion time. Besides, corrosion process led to significant surface degradation after 24h.

Tantalum has been cited to have many biomaterial applications, exhibiting biocompatibility and outstanding corrosion resistance. Tantalum may be covered with tantalum oxide using the electrochemical process of anodic oxidation. The oxide surface is known to be bioactive and more corrosion resistant. In this research, compact tantalum oxide films were obtained by potentiostatic and potentiodynamic methods in H2SO4 and H3PO4 (1 mol.L-1) electrolytes. By XPS analysis the stoichiometry Ta2O5 was detected. The thermodynamic stability of those oxides was compared and the results indicated that Ta2O5 obtained in H2SO4 has higher thermodynamic stability than Ta2O5 obtained in H3PO4. The incorporation of (PO4)3- ions and the formation of a bilayer oxide are responsible for the reduced stability. Also, the better control of chemical kinetic of oxide formation allows potentiodynamic oxides to be more stable. Ta2O5 shows spontaneous dissolution in artificial blood, nevertheless, it remains stable even after 60 days of immersion. By scratching tests was possible to notice that Ta2O5 is highly adherent to the tantalum metallic substrate and by mechanical indentation was possible to measure a lower elastic modulus for the Ta2O5 than the metallic substrate, what can be considered as distinguished properties for biomedical applications.

AbstractSeveral studies regarding superficial treatments of Nitinol (NiTi) shape-memory have been developed aiming to the improve corrosion resistance and to block the Ni release to adjacent tissues. The necessary heat treatment to achieve the shape memory effect normally occurs at temperatures between 500 and 600 °C. However, titanium oxide (TiO2) is formed on the NiTi surface during the shape memory process heat treatment. In this work the effects of the heat treatment time on the surface characteristics of the formed NiTi oxide, at temperatures that promote the shape-memory (530 and 570 °C), were evaluated. The TiO2 layers which were obtained were evaluated by X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscope (SEM), thermogravimetric analysis (TGA), wettability and roughness. The results show that by increasing the exposure time at the temperature of 570 °C the formation of a thicker oxide is promoted, with less superficial roughness and of a hydrophobic nature. According to the literature, these characteristics indicate that the obtained oxide layer has properties that accelerat the osseointegration process.

To improve the implants biocompatibility many surface modifications were proposed. Investigations about the surface modification on Ti alloys by anodic oxidation are reported. This research presents a study on the stability of thin titanium dioxide grown by potentiodynamic method on Ti6Al4V surfaces up to 5.0 V. Its bioactive surface in phosphate buffer solution (PBS) and the oxide stability after immersion in artificial blood media were measured by Electrochemical Impedance Spectroscopy (EIS). Hydroxyapatite (HAP) presence was evaluated using simulated body fluid (SBF) with different immersion times. The oxides and HAP presence were analyzed by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The oxide stability was confirmed with low dissolution rates where the Rp was around 106Ω.cm2. The results showed the TiO2 was compact and thin oxide that could prevent the severe corrosion processes and improve in few days the physical-chemical interaction of the Ti alloys with bone in physiological media.

In order to improve the NiTi alloy biocompatibility, surface treatments become very important. Nevertheless, researchers use different solutions to simulate the body fluids in electrochemical assays, and the correlation between the obtained results is difficult and might not even be possible. The present paper evaluated the electrochemical behavior of polished NiTi surfaces exposed to different simulated body fluid solutions: Hanks solution, Hanks’ balanced salt (HBSS) solution, saline body fluid (SBF) solution, and Ringer solution. The electrochemical behavior of NiTi was evaluated by open circuit potential (OCP) and cyclic voltammetry tests. The surfaces of the samples were also characterized by scanning electron microscopy, which was performed after the electrochemical tests. The results demonstrated that the NiTi alloy shows the same corrosion mechanism (pitting) in all simulated body fluids that were studied. However, the corrosion potential changes for each electrolyte, being HBSS, SBF and Ringer the most corrosive solutions. Furthermore, the Hanks and HBSS solutions demonstrated good reproducibility of the electochemical results. Considering that the HBSS represents an extreme environment, this solution seems to be the most indicated to study the corrosion behavior of NiTi treated surfaces.

The properties of melanins prepared from L-dopa oxidation by both chemical and electrochemical methods are reported, searching for a material with more intense optical absorption in the visible region. The characterization of the samples have been done by cyclic voltammetry (CV), cronoamperometry (CA), Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR) and diffuse reflectance ultraviolet-visible spectroscopy (DRUV-VIS) techniques. The electrochemical method enhanced the organic free radical (spin) concentration and the absorption intensity in the visible region of the spectrum. The DRUV-VIS technique along with mathematical tools, such as the Kubelka-Munk remission function, were good options for the characterization of the final products.