Design of titanium-copolymer sandwich materials for biomedical applications

Les lésions crâniennes causées par des accidents, traumatismes et pathologies sont fréquentes et nécessitent la reconstruction de la région crânio-maxillo-faciale (CMF). Actuellement, les biomatériaux les plus utilisés pour fabriquer des prothèses crâniennes et mandibulaires sont sous forme de monomatériaux. En raison de sa biocompatibilité, le titane (Ti) est généralement utilisé dans la fabrication de plaques d’ostéosynthèse pour remplacer l’os. Cependant, la différence significative des propriétés mécaniques entre le Ti et les tissus environnants se traduit par un “stress-shielding” préjudiciable à l’os voisin de la prothèse. Pour atténuer cet effet, un procédé d’élaboration de matériaux sandwichs (SMs pour “sandwich materials”) - dans lesquels deux plaques métalliques et un cœur de polymère sont alternativement superposés - a été étudié. Toutefois, du fait de leur cytotoxicité, les résines époxy généralement utilisées dans l’industrie pour réaliser l’interface, ne peuvent l’être dans le domaine biomédical. Le projet de thèse consiste en le développement de SMs biocompatibles (bioSMs pour “biocompatible sandwich materials”) dans le cadre de la chirurgie CMF. Dans de récentes études au laboratoire, le greffage de poly(méthacrylate de méthyle (PMMA) sur des substrats en Ti a été développé en utilisant la méthode “grafting from” pour former une première génération de bioSMs. Dans la seconde génération, le PMMA a été remplacé par un copolymère statistique - le poly(méthacrylate de méthyle-co-méthacrylate de n-butyle) P(MMA-ran-BMA) - afin d’améliorer la mise en forme et l’adhésion de l’interface à température ambiante (Tamb).Cranial injuries caused by accidents, traumas and pathologies are frequent and require the reconstruction of the craniomaxillofacial (CMF) region. Currently, the biomaterials most used to manufacture skull and mandible prostheses are in the form of monomaterials. Due to its biocompatibility, titanium (Ti) is generally used to built-up osteosynthesis plates to replace bones. However, the significant difference of the mechanical properties between Ti and the surrounding tissues results in a “stress-shielding” detrimental to the bones close to the prosthesis. To reduce this effect, a process for producing sandwich materials (SMs) - in which two metallic plates and a polymer core are alternatively superposed - was studied. However, due to their cytotoxicity, the epoxy resins generally used in industry to achieve the interface cannot be used in the biomedical field. The research project consists of the development of biocompatible SMs (bioSMs) in the context of CMF surgery. In recent laboratory studies at IPCMS, the grafting of poly(methyl methacrylate) (PMMA) onto Ti substrates was developed using the “grafting from” method to form a first generation of bioSMs. In the second generation, the PMMA has been replaced by a random copolymer - poly(methyl methacrylate-co-n-butyl methacrylate) P(MMA-ran-BMA) - in order to improve the shaping and the adhesion interface at room temperature

Adhesion Behavior of Ti–PMMA–Ti Sandwiches for Biomedical Applications

International audienceAbstract The “stress-shielding” problem, common with metallic implants, may be solved by using biocompatible sandwiches with a polymeric core between two metallic skin sheets. To achieve such sandwiches, a process route has been developed, beginning with the grafting of poly-(methyl-methacrylate) (PMMA) on titanium (Ti) sheets via the “grafting from” technique. Grafting resulted in variable thicknesses of PMMA on the Ti sheets. Hot-pressing was used to prepare semi-finished Ti–PMMA–Ti sandwiches. The adhesion was achieved by the interpenetration between PMMA sheet and the grafted PMMA chains. Investigation was carried out to understand the influence of the grafted PMMA thickness on the adhesion strength. Similar adhesion strengths were found for the sandwiches despite variable grafted PMMA thicknesses, indicating a successful grafting of PMMA on large-scale Ti sheets. The adhesion followed the autohesion theory, where a time-dependent increase in adhesion strength was found for the sandwiches

Effect of Mg Addition and PMMA Coating on the Biodegradation Behaviour of Extruded Zn Material

Although zinc (Zn) is one of the elements with the greatest potential for biodegradable uses, pure Zn does not have the ideal mechanical or degrading properties for orthopaedic applications. The current research aims at studying the microstructure and corrosion behaviour of pure Zn (used as a reference material) and Zn alloyed with 1.89 wt.% magnesium (Mg), both in their extruded states as well as after being coated with polymethyl methacrylate (PMMA). The grafting-from approach was used to create a PMMA covering. The “grafting-from” method entails three steps: the alkali activation of the alloys, their functionalization with an initiator of polymerization through a phosphonate-attaching group, and the surface-initiated atom transfer radical polymerisation (SI-ATRP) to grow PMMA chains. Electrochemical and immersion corrosion tests were carried out in a simulated body fluid (SBF), and both confirmed the enhanced corrosion behaviour obtained after coating. The electrochemical test revealed a decrease in the degradation rate of the alloy from 0.37 ± 0.14 mm/y to 0.22 ± 0.01 mm/y. The immersion test showed the ability of complete protection for 240 h. After 720 h of immersion, the coated alloy displays minute crevice corrosion with very trivial pitting compared to the severe localized (galvanic and pitting) corrosion type that was detected in the bare alloy

Trends in Metal-Based Composite Biomaterials for Hard Tissue Applications

International audienceAbstract The world of biomaterials has been continuously evolving. Where in the past only mono-material implants were used, the growth in technology and collaboration between researchers from different sectors has led to a tremendous improvement in implant industry. Nowadays, composite materials are one of the leading research areas for biomedical applications. When we look toward hard tissue applications, metal-based composites seem to be desirable candidates. Metals provide the mechanical and physical properties needed for load-bearing applications, which when merged with beneficial properties of bioceramics/polymers can help in the creation of remarkable bioactive as well biodegradable implants. Keeping this in mind, this review will focus on various production routes of metal-based composite materials for hard tissue applications. Where possible, the pros and cons of the techniques have been provided