Creation of a Composite Bioactive Coating with Antibacterial Effect Promising for Bone Implantation.

When creating titanium-containing bone implants, the bioactive coatings that promote their rapid engraftment are important. The engraftment rate of titanium implants with bone tissue depends significantly on the modification of the implant surface. It is achieved by changing either the relief or the chemical composition of the surface layer, as well as a combination of these two factors. In this work, we studied the creation of composite coatings with a two-level (the micro- and nanolevel) hierarchy of the surface relief, which have bioactive and bactericidal properties, which are promising for bone implantation. Using the developed non-lithographic template electrochemical synthesis, a composite coating on titanium with a controlled surface structure was created based on an island-type TiO2 film, silver and hydroxyapatite (HAp). This TiO2/Ag/HAp composite coating has a developed surface relief at the micro- and nanolevels and has a significant cytological response and the ability to accelerate osteosynthesis, and also has an antibacterial effect. Thus, the developed biomaterial is suitable for production of dental and orthopedic implants with improved biomedical properties.

Features of Fabrication of Titanium Dioxide Based Coatings for Non-Lithographic Template Electrochemical Synthesis of Micron Metal Particle Arrays.

This work is devoted to the development of non-lithographic template methods of synthesis. These methods have a significant advantage in terms of structure formation: there is no need to design and produce masks, which greatly simplifies the process, and more of them can work with nonplanar substrates. The purpose of this study was to reveal the conditions for the synthesis of titanium dioxide xerogel films of different topologies as well as to develop a technique for non-lithographic template electrochemical synthesis of micron metal particles arrays and to study the structure of the resulting coatings. The films were deposited on the surface of substrates via dip coating. Specific topology of the films was achieved by template sol-gel synthesis. Their structures were analyzed by SEM and XRD. Template synthesis of metal micro particles were realized by pulsed electrochemical deposition of metals into the perforations of xerogel films. Obtained materials were analyzed by SEM and XRD; the element distribution on the surface was determined by the EDS detector of SEM. Based on the analysis results, we suggest the mechanisms of formation of the xerogel topology and proved the efficiency of pulsed electrodeposition for template synthesis of micron particles arrays.

Features of the Synthesis of the Dispersed TiC Phase with Nickel Nanostructures on the Surface to Create an Aluminum-Based Metal Composite.

The development of new composites with improved functional properties is the important task of modern materials science. The composites must be structurally organized to provide improved properties. For metal-ceramic composites, there is a need for a uniform distribution of the dispersed ceramic phase in the bulk metallic matrix The modification of the dispersed ceramic phase surface with a metal coating is one of the more effective ways to accomplish this. Particularly, in this work, the conditions of Ni nanolayer deposition on titanium carbide (TiC) particles were studied. The goal was to create core-shell particles with a thickness of the Ni coating on TiC not exceeding 90 nm. Preliminary work was also carried out to study the effect of the dispersed phase composition on the mechanical properties of the composite with an Al matrix.

Conditions for Production of Composite Material Based on Aluminum and Carbon Nanofibers and Its Physic-Mechanical Properties.

Aluminum-based metallic matrix composites reinforced by carbon nanofibers (CNFs) are important precursors for development of new light and ultralight materials with enhanced properties and high specific characteristics. In the present work, powder metallurgy technique was applied for production of composites based on reinforcement of aluminum matrices by CNFs of different concentrations (0~2.5 wt%). CNFs were produced by chemical vapor deposition (CVD) and mechanical activation. We determined that in situ synthesis of carbon nanostructures with subsequent mechanic activation provides satisfactory distribution of nanofibers and homogeneous composite microstructure. Introduction of 1 vol% of flux (0.25 NaCl + 0.25 KCl + 0.5 CaF2) during mechanic activation helps to reduce the strength of the contacts between the particles. Additionally, better reinforcement of alumina particles and strengthening the bond between CNFs and aluminum are observed due to alumina film removal. Introduction of pure aluminum into mechanically alloyed powder provides the possibility to control composite durability, plasticity and thermal conductivity.

Improved osseointegration properties of hierarchical microtopographic/nanotopographic coatings fabricated on titanium implants.

BACKGROUND: Titanium (Ti) implants are extensively used in reconstructive surgery and orthopedics. However, the intrinsic inertness of untreated Ti implants usually results in insufficient osseointegration. In order to improve the osteoconductivity properties of the implants, they are coated with hierarchical microtopographic/nanotopographic coatings employing the method of molecular layering of atomic layer deposition (ML-ALD). RESULTS: The analysis of the fabricated nanostructured relief employing scanning electron microscopy, atomic force microscopy, and electron spectroscopy for chemical analysis clearly demonstrated the formation of the nanotopographic (<100 nm) and microtopographic (0.1-0.5 µm) titano-organic structures on the surface of the nanograined Ti implants. Subsequent coincubation of the MC3T3-E1 mouse osteoblasts on the microtopographic/nanotopographic surface of the implants resulted in enhanced osteogenic cell differentiation (the production of alkaline phosphatase, osteopontin, and osteocalcin). In vivo assessment of the osseointegrative properties of the microtopographically/nanotopographically coated implants in a model of below-knee amputation in New Zealand rabbits demonstrated enhanced new bone formation in the zone of the bone-implant contact (as measured by X-ray study) and increased osseointegration strength (removal torque measurements). CONCLUSION: The fabrication of the hierarchical microtopographic/nanotopographic coatings on the nanograined Ti implants significantly improves the osseointegrative properties of the intraosseous Ti implants. This effect could be employed in both translational and clinical studies in orthopedic and reconstructive surgery.

Enhanced Osseointegrative Properties of Ultra-Fine-Grained Titanium Implants Modified by Chemical Etching and Atomic Layer Deposition.

An integrated approach combining severe plastic deformation (SPD), chemical etching (CE), and atomic layer deposition (ALD) was used to produce titanium implants with enhanced osseointegration. The relationship between morphology, topography, surface composition, and bioactivity of ultra-fine-grained (UFG) titanium modified by CE and ALD was studied in detail. The topography and morphology have been studied by means of atomic force microscopy, scanning electron microscopy, and the spectral ellipsometry. The composition and structure have been determined by X-ray fluorescence analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The wettability of the surfaces was examined by the contact angle measurement. The bioactivity and biocompatibility of the samples were studied in vitro and in vivo. CE of UFG titanium in basic (NH4OH/H2O2) or acidic (H2SO4/H2O2) piranha solution significantly enhances the surface roughness and leads to microstructures, nanostructures, and hierarchical micro-/nanostructures on the surfaces. In vitro results demonstrate deterioration of adhesion, proliferation, and differentiation of MC3T3-E1 osteoblasts cell for CE samples as compared to the non-treated ones. Atomic layer deposition of crystalline titanium oxide onto the CE samples increased hydrophilicity, changed the surface composition, and enhanced significantly in vitro characteristics. In vivo experiments demonstrated non-toxicity of the implants. Etching in basic piranha solution with subsequent ALD significantly improved implant osseointegration as compared with the non-modified samples.

Bioactive Coating with Two-Layer Hierarchy of Relief Obtained by Sol-Gel Method with Shock Drying and Osteoblast Response of Its Structure.

In this work, we analyze the efficiency of the modification of the implant surface. This modification was reached by the formation of a two-level relief hierarchy by means of a sol-gel approach that included dip coating with subsequent shock drying. Using this method, we fabricated a nanoporous layer with micron-sized defects on the nanotitanium surface. The present work continues an earlier study by our group, wherein the effect of osteoblast-like cell adhesion acceleration was found. In the present paper, we give the results of more detailed evaluation of coating efficiency. Specifically, cytological analysis was performed that included the study of the marker levels of osteoblast-like cell differentiation. We found a significant increase in the activity of alkaline phosphatase at the initial incubation stage. This is very important for implantation, since such an effect assists the decrease in the induction time of implant engraftment. Moreover, osteopontin expression remains high for long expositions. This indicates a prolonged osteogenic effect in the coating. The results suggest the acceleration of the pre-implant area mineralization and, correspondingly, the potential use of the developed coatings for bone implantation.

Modification of the Surface Topography and Composition of Ultrafine and Coarse Grained Titanium by Chemical Etching.

In this study, we present the detailed investigation of the influence of the etching medium (acidic or basic Piranha solutions) and the etching time on the morphology and surface relief of ultrafine grained (UFG) and coarse grained (CG) titanium. The surface relief and morphology have been studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), and the spectral ellipsometry. The composition of the samples has been determined by X-ray fluorescence analysis (XRF) and X-ray Photoelectron Spectroscopy (XPS). Significant difference in the etching behavior of UFG and CG titanium has been found. UFG titanium exhibits higher etching activity independently of the etching medium. Formed structures possess higher homogeneity. The variation of the etching medium and time leads to micro-, nano-, or hierarchical micro/nanostructures on the surface. Significant difference has been found between surface composition for UFG titanium etched in basic and acidic Piranha solution. Based on the experimental data, the possible reasons and mechanisms are considered for the formation of nano- and microstructures. The prospects of etched UFG titanium as the material for implants are discussed.

Two-Level Micro-to-Nanoscale Hierarchical TiO2 Nanolayers on Titanium Surface.

Joint replacement is being actively developed within modern orthopedics. One novel material providing fast implantation is bioactive coatings. The synthesis of targeted nanocoatings on metallic nanotitanium surface is reported in this paper. TiO2-based micro- and nanocoatings were produced by sol-gel synthesis using dip-coating technology with subsequent fast (shock) drying in hot plate mode at 400 °C. As a result of shock drying, the two-level hierarchical TiO2 nanolayer on the nanotitanium was obtained. This two-level hierarchy includes nanorelief of porous xerogel and microrelief of the micron-sized "defect" network (a crack network). The thickness of TiO2 nanolayers was controlled by repeating dip-coating process the necessary number of times after the first layer deposition. The state of the MS3T3-E1 osteoblast cell line (young cells that form bone tissue) on the two-level hierarchical surface has been studied. Particularly, adhesion character, adhesion time and morphology have been studied. The reported results may serve the starting point for the development of novel bioactive coatings for bone and teeth implants.

Formation of Micro- and Nanostructures on the Nanotitanium Surface by Chemical Etching and Deposition of Titania Films by Atomic Layer Deposition (ALD).

In this study, an integrated approach was used for the preparation of a nanotitanium-based bioactive material. The integrated approach included three methods: severe plastic deformation (SPD), chemical etching and atomic layer deposition (ALD). For the first time, it was experimentally shown that the nature of the etching medium (acidic or basic Piranha solutions) and the etching time have a significant qualitative impact on the nanotitanium surface structure both at the nano- and microscale. The etched samples were coated with crystalline biocompatible TiO2 films with a thickness of 20 nm by Atomic Layer Deposition (ALD). Comparative study of the adhesive and spreading properties of human osteoblasts MG-63 has demonstrated that presence of nano- and microscale structures and crystalline titanium oxide on the surface of nanotitanium improve bioactive properties of the material.