Structure and Properties of Bioactive Titanium Dioxide Surface Layers Produced on NiTi Shape Memory Alloy in Low-Temperature Plasma.

BACKGROUND: The NiTi alloy, known for its shape memory and superelasticity, is increasingly used in medicine. However, its high nickel content requires enhanced biocompatibility for long-term implants. Low-temperature plasma treatments under glow-discharge conditions can improve surface properties without compromising mechanical integrity. METHODS: This study explores the surface modification of a NiTi alloy by oxidizing it in low-temperature plasma. We examine the impact of process temperatures and sample preparation (mechanical grinding and polishing) on the structure of the produced titanium oxide layers. Surface properties, including topography, morphology, chemical composition, and bioactivity, were analyzed using TEM, SEM, EDS, and an optical profilometer. Bioactivity was assessed through the deposition of calcium phosphate in simulated body fluid (SBF). RESULTS: The low-temperature plasma oxidization produced titanium dioxide layers (29-55 nm thick) with a predominantly nanocrystalline rutile structure. Layer thickness increased with extended processing time and higher temperatures (up to 390 °C), though the relationship was not linear. Higher temperatures led to thicker layers with more precipitates and inhomogeneities. The oxidized layers showed increased bioactivity after 14 and 30 days in SBF. CONCLUSIONS: Low-temperature plasma oxidation produces bioactive titanium oxide layers on NiTi alloys, with a structure and properties that can be tuned through process parameters. This method could enhance the biocompatibility of NiTi alloys for medical implants.

Influence of Low Temperature Plasma Oxidizing on the Bioactivity of NiTi Shape Memory Alloy for Medical Applications.

The present study elucidates the impact of glow discharge oxidation within a low-temperature plasma environment on the bioactivity characteristics of an NiTi shape memory alloy. The properties of the produced surface layers, such as structure (TEM observations), surface morphology (SEM observations), chemical and phase composition (EDS and XRD measurements), wettability (optical gonimeter), and the biological response of osteoblasts and platelets to the oxidized surface compared with the NiTi alloy without a surface layer are presented. The presented surface modification of the NiTi shape memory alloy, achieved through oxidizing in a low-temperature plasma environment, led to the creation of a continuous surface layer composed of nanocrystalline titanium oxide TiO2 (rutile). The findings obtained from this study provide evidence that the oxidized layer augments the bioactivity of the shape memory alloy. This augmentation was substantiated through the spontaneous biomimetic deposition of apatite from a simulated body fluid (SBF) solution. Furthermore, the modified surface exhibited improved osteoblast proliferation, and enhanced platelet adhesion and activation. This proposed surface modification strategy holds promise as a prospective solution to enhance the biocompatibility and bioactivity of NiTi shape memory alloy intended for prolonged use in bone implant applications.

New technology can benefit established middle ear implant users: Samba 2 vs previous models of audio processors for Vibrant Soundbridge.

INTRODUCTION: The Vibrant Soundbridge (VSB) is a semi-implantable hearing aid for patients with various types of hearing loss and has been available for over 25 years. Recently, new audio processors with advanced signal processing, noise reduction, and multi-microphone technology have appeared. The aim of this study is to compare the benefits of using the newest Samba 2 processor to the previous generation processors in a group of experienced VSB users. METHODS: There were 22 experienced VSB users (mean time of using VSB was 9 years, SD = 2) who had their processor (D404 or Amadé) upgraded to the newest model (Samba 2). The mean age of the subjects was 56 years (SD = 20). Assessments were made by free-field audiometry, speech reception in quiet and noise, and Patient-Reported Outcome Measures (PROMs). RESULTS: Hearing tests in free field showed statistically significant improvements in hearing sensitivity and speech discrimination in quiet and noise with the Samba 2 audio processor compared to the earlier technology. PROMs confirmed the benefits of using the newest audio processor and there was more satisfaction in terms of usability. CONCLUSIONS: Access to modern technology for VSB patients provides measurable benefits.

Plasma Modification of Carbon Coating Produced by RF CVD on Oxidized NiTi Shape Memory Alloy under Glow-Discharge Conditions.

Our previous work has shown that for cardiac applications, combining low-temperature plasma oxidation with an amorphous carbon coating (a-C:N:H type) constitutes a prospective solution. In this study, a short-term modification by low-temperature oxygen plasma is proposed as an example and a method for shaping the topography and surface energy of the outer amorphous carbon coating, produced via the Radio-Frequency Chemical Vapour Deposition (RFCVD) method on NiTi alloy oxidized under glow-discharge conditions. This treatment alters the chemical composition of the outer zone of the surface layer. A slight increase is also noted in the surface roughness at the nanoscale. The contact angles were shown to increase by about 20% for water and 30% for diiodomethane, while the surface free energy decreased by ca. 11%. The obtained results indicate that even short-term contact with low-temperature plasma can shape the surface properties of the carbon coating, an outcome which shows potential in terms of its use in medical applications.

Formation of Nitrogen Doped Titanium Dioxide Surface Layer on NiTi Shape Memory Alloy.

NiTi shape memory alloys are increasingly being used as bone and cardiac implants. The oxide layer of nanometric thickness spontaneously formed on their surface does not sufficiently protect from nickel transition into surrounding tissues, and its presence, even in a small amount, can be harmful to the human organism. In order to limit this disadvantageous phenomenon, there are several surface engineering techniques used, including oxidation methods. Due to the usually complex shapes of implants, one of the most prospective methods is low-temperature plasma oxidation. This article presents the role of cathode sputtering in the formation of a titanium dioxide surface layer, specifically rutile. The surface of the NiTi shape memory alloy was modified using low-temperature glow discharge plasma oxidation processes, which were carried out in two variants: oxidation using an argon + oxygen (80% vol.) reactive atmosphere and the less chemically active argon + air (80% vol.), but with a preliminary cathode sputtering process in the Ar + N2 (1:1) plasma. This paper presents the structure (STEM), chemical composition (EDS, SIMS), surface topography (optical profilometer, Atomic Force Microscopy-AFM) and antibacterial properties of nanocrystalline TiO2 diffusive surface layers. It is shown that prior cathodic sputtering in argon-nitrogen plasma almost doubled the thickness of the produced nitrogen-doped titanium dioxide layers despite using air instead of oxygen. The (TiOxNy)2 diffusive surface layer showed a high level of resistance to E. coli colonization in comparison with NiTi, which indicates the possibility of using this surface layer in the modification of NiTi implants' properties.

Structure and properties of composite surface layers produced on NiTi shape memory alloy by a hybrid method.

A hybrid process that combines oxidation under glow-discharge conditions with ion beam-assisted deposition (IBAD) has been applied to mechanically polished NiTi shape memory alloy in order to produce composite surface layers consisting of a TiO2 layer and an external carbon coating with an addition of silver. The produced surface layers a-C(Ag) + TiO2 type have shown increased surface roughness, improved corrosion resistance, altered wettability, and surface free energy, as well as reduced platelet adhesion, aggregation, and activation in comparison to NiTi alloy in initial state. Such characteristics can be of great benefit for cardiac applications.

Multi-scale characterization and biological evaluation of composite surface layers produced under glow discharge conditions on NiTi shape memory alloy for potential cardiological application.

NiTi shape memory alloys are characterized by relatively good biocompatibility primarily thanks to their ability to self-passivate. However, before they can be used as medical implants for long term use, they need to undergo treatment aimed at producing layers on their surface that are superior to spontaneously formed oxide layers and that would increase their resistance to corrosion, limit nickel ion release from the surface (metallosis) and have the capability to shape their biological properties depending on the application. Furthermore, cardiac implants require addressing the issue of blood clotting on the surface. Treatment in glow-discharge low temperature plasma makes it possible to produce titanium layers with a structure and properties that are controlled via process parameters. In addition, antithrombogenic properties can be improved by depositing a carbon coating via the RFCVD process. The aim of the study was to investigate the structure, surface topography, adhesive properties, wettability, surface free energy and evaluate metallosis after producing TiO2 and a-C:N:H + TiO2 composite layers on NiTi alloy. The capabilities of AFM microscopes in studying the adhesive properties of a surface were also highlighted in the study. The study shows that the produced surface layers are capable of significantly reducing metallosis. Furthermore, in contrast to NiTi in its initial state, layers of nanocrystalline TiO2 titanium oxide (rutile) with a homogeneous structure demonstrate greater adhesion strength and more developed surface in the microscale, which facilitates the formation of an a-C:N:H coating. Therefore the formation of a coating of a-C:N:H amorphous carbon on NiTi alloy that has previously been oxidised in low-temperature plasma may prove to be a favourable solution in terms of using NiTi alloy to produce cardiac implants.

Hybrid a-CNH+TiO2+TiN-type surface layers produced on NiTi shape memory alloy for cardiovascular applications.

AIM: The goal was to improve the properties of NiTi shape memory alloy to make it suitable for cardiac applications. For this purpose, a hybrid a-CNH+TiO2+TiN-type surface layer was produced on NiTi alloy and characterized. MATERIALS & METHODS: The NiTi alloy subjected to hybrid process combining low-temperature oxynitriding under glow discharge conditions and radio frequency chemical vapor deposition process was examined for microstructure, surface topography, corrosion resistance, wettability and surface-free energy, Ni ion release and platelets adhesion, aggregation and activation. RESULTS: The hybrid surface layers showed slightly increased surface roughness, better corrosion resistance, a more hydrophobic nature, decreased surface free energy, smaller release of nickel ions and reduced platelets activation. CONCLUSION: The produced layers could expand the range of NiTi medical applications.

[Changes in the lipid content of erythrocytes in patients with chronic renal failure]. / Zmiany skladu lipidowego blon erytrocytów osób z przewlekla niewydolnoscia nerek.

The oxidative stress accompanying chronic renal failure may cause a number of harmful changes in the organism of a human being. Hemodialysis, as one of the treatment methods of chronic renal failure, increases the oxidative stress, whose destructive activity is among other things manifested by changes in the lipid profile of the membranes of erythrocytes (RBC). Disturbances in the decomposition of membrane phospholipids are the causes of a lowered viability of red blood cells and an increased oligocytosis among hemodialysed patients. So far, reports do not, however, explain in a complex way the mechanism of how reactive oxygen species affect the functioning and the lipid profile of the cell membranes of erythrocytes. Besides, studies devoted to the mentioned problem provide contradictory results. It is being searched for new ways of decreasing the effects of the oxidative stress among patients with chronic illnesses in which free radicals are at the basis. One of the most frequently used methods of dialysis therapy is the usage of polysulfone membranes which to a great degree decrease the unwanted effects of hemodialysis. The information included in this work refer to data describing the effect of the oxidative stress in chronic renal failure, hemodialysis and preventive ways of decreasing the negative effects of an increased action of reactive oxygen species.