Christelle Arnould

Titanium modified with layer-by-layer sol-gel tantalum oxide and an organodiphosphonic acid: A coating for hydroxyapatite growth

Titanium and its alloys are widely used in surgical implants due to their appropriate properties like corrosion resistance, biocompatibility, and load bearing. Unfortunately when metals are used for orthopedic and dental implants there is the possibility of loosening over a long period of time. Surface modification is a good way to counter this problem. A thin tantalum oxide layer obtained by layer-by-layer (LBL) sol-gel deposition on top of a titanium surface is expected to improve biocorrosion resistance in the body fluid, biocompatibility, and radio-opacity. This elaboration step is followed by a modification of the tantalum oxide surface with an organodiphosphonic acid self-assembled monolayer, capable of chemically binding to the oxide surface, and also improving hydroxyapatite growth. The different steps of this proposed process are characterized by surfaces techniques like contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM).

Tantalum oxide/carbon nanotubes composite coatings on titanium, and their functionalization with organophosphonic molecular films: A high quality scaffold for hydroxyapatite growth

Nowadays, titanium is a very commonly used biomaterial for the preparation of orthopedic and dental implants. Its excellent mechanical and biochemical bulk properties are nevertheless counterbalanced by its propensity to long term degradation in physiological conditions and its weak osseointegrative capacities. In this context, surface modifications can significantly hinder titanium weaknesses. The approach considered in this work relies on the preparation of thin composite coatings based on tantalum oxide and carbon nanotubes by sol-gel process. Tantalum is particularly interesting for its high biocompatibility and bioactivity, as well as its strong resistance to bio-corrosion. Carbon nanotubes are exploited to reinforce the compactness and homogeneity of the coatings, and can act as a favorable factor to strengthen the interaction with bone components by biomimicry. The composite layers are further modified with specific organophosphonic acid molecular films, able to chemically bind the tantalum oxide surface and improve the hydroxyapatite formation process. The characteristics and the qualities of these hybrid inorganic/organic coatings are evaluated by XPS, SEM, TEM, peeling tests, contact angle measurements, and electrochemical characterizations (free potential, polarization curves).

Fabrication of tantalum oxide/carbon nanotubes thin film composite on titanium substrate

The development of new biomaterials is one of the most challenging tasks in material science. Metals and particularly titanium and its alloys are widely used because of their good corrosion resistance, mechanical properties and biocompatibility. However, the toxicity of alloys, long term degradation in body fluids and risks of loosening are still problematic. To increase the corrosion resistance of the material and reduce ion release, our interest focused on tantalum, another metal well known for its excellent biocompatibility and resistance to bio-corrosion. These very good properties make tantalum a metal of interest for biomaterials but its high cost and high density disqualify it for use as bulk material. In this paper, we propose to combine the good bulk properties of titanium with the excellent surface properties of tantalum by using sol-gel deposition of a tantalum oxide layer on bare titanium. Furthermore, as orthopedics implants are part of our long term goals, we report on the formation of a composite layer of tantalum oxide and multiwalled carbon nanotubes (MWCNTs). MWCNTs have been shown to have promising properties in contact with bone and bone cells and could strengthen the implant. Characterizations are performed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).

Electrodeposition from Ionic Liquid of 2D Ordered Ta2O5 on Titanium Substrate Through a Polystyrene Template

Microstructuration of a protective tantalum oxide layer was investigated by the combination of substrate surface patterning with colloidal particles and electroreduction of TaF 5 in ionic liquid. The formation of a two-dimensionally (2D) ordered monolayer of polystyrene particles was achieved on a square centimeter area using a facile method, which does not require additives or specific apparatus. Parameters of a previously reported protocol for tantalum electrodeposition on bare titanium were optimized to retain the integrity of the 2D ordered monolayer of polystyrene particles, and also to lead to the formation of a dense, homogeneous, adherent, and passivating structured layer of Ta 2 O 5 .

Bilayers Coating on Titanium Surface: The impact on the Hydroxyapatite Initiation

Most of the actual orthopaedic devices, widely made of titanium and its alloys, present different weaknesses like ions release and risks of loosening over a long period. To solve such problems, new developments in surface modification are crucial. This work is an extension of our recent effort on the development and improvement of a multifunctional inorganic/organic bilayers coating. A thin tantalum oxide layer is formed by sol-gel synthesis followed by the modification with organophosphonic acids of the tantalum oxide layer. We focus in particular on the effect of the bilayers coating on corrosion resistance and hydroxyapatite growth rate by immersion in a simulated body fluid solution. It is also highlighted that the structure of the organophosphonic acid is of major importance on the osteoinduction character of the material.