|Wednesday, August 26|
The grain refinement effect of gadolinium in magnesium at modified extrusion ratio
* Sebastian Meyer, Helmholtz-Zentrum-Geesthacht, Germany
Björn Wiese, Helmholtz-Zentrum-Geesthacht, Germany
Jan Bohlen, Helmholtz-Zentrum-Geesthacht, Germany
Thomas Ebel, Helmholtz-Zentrum-Geesthacht, Germany
Regine Willumeit-Römer, Helmholtz-Zentrum-Geesthacht, Germany
Hot extrusion is an established process to form semi-finished products with bioactive magnesium alloys. Grain size, hardness, yield strength and texture give a good overview about the microstructure evolved with higher extrusion ratio and gadolinium content. Grain refinement effects are shown in MgGd as well as with high extrusion ratio of 1:69 for pure Mg and MgGd. The texture reveals full recrystalisation and contributes to mechanical properties with low tensile and compression asymetry in MgGd.
Investigation on ternary ZnAl-Li alloys as potential materials for cardio-vascular and orthopaedic implants
* Ehsan Farabi, Institute for Frontier Materials, Deakin University, Australia
Alireza Vahid, Institute for Frontier Materials, Deakin University, Australia
Santiago Corujeira Gallo, Institute for Frontier Materials, Deakin University, Australia
Daniel M. Fabijanic, Institute for Frontier Materials, Deakin University, Australia
Matthew R. Barnett, Institute for Frontier Materials, Deakin University, Australia
The biodegradable Zinc alloys have become a promising candidate for the cardiovascular stent and orthopaedic applications. However, their lower strength and ductility have limited their applications for biomedical purposes. In this study, a new biodegradable zinc alloy with enhanced properties was developed using a novel rapid alloy development technique to avoid the labour incentive and costly experiments associated with alloy optimization. Here, the ternary Zn-Al-Li alloy system was investigated and the tensile strength, ductility and in-vitro corrosion behaviour for a range of alloys were optimized. It was found that for higher values of lithium (0.6 wt.%) and aluminium (4 wt.%) the ultimate tensile strength (i.e., 450 MPa) and ductility (i.e., 45% elongation) of the alloy was significantly improved. In parallel, the in-vitro corrosion behaviour of the developed alloys was measured in simulated body fluid using the immersion and potentiodynamic tests. The obtained results were close to in-vivo degradation rates of the pure zinc indicating sustainability of the developed materials for the biomedical applications. These findings shows promising applicability of the technique for investigating the complex Zn alloy systems and encourages further exploration for developing high strength biodegradable zinc alloys.
Anodized AZ91D magnesium alloy: electrochemical, surface and cell culturing studio
Julieta Merlo, INTEMA - University of Mar del Plata-CONICET, Argentina
Julieta Moreno, INTEMA - University of Mar del Plata-CONICET, Argentina
Francisco Buchelly, ICYTE-CONICET-UNMdP
Juan Pastore, ICYTE-CONICET-UNMdP
Andrea Gomez Sanchez, CIT Villa María CONICET
Maria Rosa Katunar, INTEMA - University of Mar del Plata-CONICET
* Silvia Ceré, INTEMA - University of Mar del Plata-CONICET, Argentina
Anodizing is one alternative, but many of the protocols used included hazardous compounds (e.g. chromates or fluorides) or high current densities. In the present study AZ91D Mg alloy was anodized with an environmentally-friendly low cost process, with the aim of controlling hydrogen evolution generating a potential material for orthopaedic devices. Surface was studied by Raman Spectroscopy, SEM, and roughness was assessed using a profilometer. Electrochemical tests (polarization curves and EIS) were conducted in simulated body fluid at 37° C. The influence of the anodizing on the cellular adhesion and viability was assessed using primary culture bovine embryonic fibroblasts (BEFs) and the pre-osteoblastic cell line MC3T3-E1, respectively. Anodized samples showed low hydrogen evolution and improvement of cell adhesion and viability.
Improving degradation behavior of bioresorbable Mg-Zn-Ca alloys by addition of lithium
* Chiamaka Okafor, Florida International University, United States
Norman Munroe, Florida International University, United States
Mg-Zn-Ca alloys have received significant interest as bioresorbable implant materials amongst others because they possess superior mechanical properties and lower degradation rates. However, they still exhibit less than desirable biodegradation behavior. Here, the addition of lithium to Mg-Zn-Ca is investigated as a viable option for improving degradation properties due to a decrease of secondary phases and the formation of a more reliable lithium carbonate coating. Furthermore, the addition of lithium enhances alloy ductility and material formability. Degradation behavior of novel Mg-Li-Zn-Ca alloys is assessed using electrochemical impedance spectroscopy. The morphology of the alloys is studied using scanning electron microscopy and x-ray diffraction. Mechanical properties including hardness are evaluated by nanoindentation, and corrosion rates are accessed by immersion tests in Hank’s balanced salt solution at 37 oC and 4% CO2 environment.
Improving bioactive and antibacterial performance by designed hybrid coatings of degradable magnesium implants
* Julieta Merlo, INTEMA, Argentina
Silvia Ceré, INTEMA, Argentina
Aldo Boccaccini, University of Erlangen-Nurenberg, Germany
Josefina Ballarre, INTEMA, Argentina
Magnesium alloys are promising candidate materials for bio-absorbable fracture fixation devices but their fast corrosion in aqueous media generates hydrogen gas evolution. In this study, a hybrid biocompatible and bioactive coating system composed by a sol-gel silica based matrix with bioactive glass micro particles and silica-gentamicin nanoparticles was developed and applied through spray deposition. This coating system was intended to decrease the magnesium alloy degradation, but also to provide bioactive and antibacterial properties to the implant surface. The hybrid coating was homogeneously distributed on the surface, presented bioactivity in simulated body fluid and retarded degradation of the AZ91D alloy. Inhibition of bacteria growth was proved for Staphylococcus aureus and Escherichia coli after 9h of direct contact with bacteria suspensions. Moreover, compared with the non-coated AZ91D substrates, the coated specimens increased the viability of bone marrow ST-2 cells by day 7, and promoted the osteoblast differentiation of MC3T3-E1 cells. The proposed hybrid coating is a promising surface treatment for developing a new generation of degradable implants with enhanced surface functionalities.
Tailoring Properties of Fe-based Biodegradable Metals by Grain Refinement: A Review
* Camillus Obayi, University of Nigeria, Nigeria
Paul Nnamchi, University of Nigeria, Nigeria
Overtime researches on the development of Fe-based biodegradable metals for stent application have indicated that grain size moderation could be a viable tool for tailoring the properties of Fe-based metals. These properties are uniform in vivo degradation rate ≤ 20 µm/year  and adequate biocompatibility; standardized grain size range (10-30 µm) [2, 3], sufficient strength (yield strength > 200MPa; tensile strength > 300 MPa) to preserve its load-bearing function and adequate ductility (>15-18%) for safe deployment during implantation [2, 6]. This review is aimed at showing that grain refinement benefits the above required properties by reviewing pertinent works on Fe-based Biometals. The outcome of this review indicated that since the grain size range of stent materials is standardized and their properties are grain-size dependent, grain size moderation remains a viable option for tailoring properties of Fe-based biodegradable stent metals
The preparation and characterization of Ag/Mg-Al LDHs coating via in situ growth on magnesium alloys
Yun Zhao, Tianjin University of Technology, China
Wei Wang, Tianjin University of Technology, China
Yangping Chen, Tianjin University of Technology, China
Minfang Chen, Tianjin University of Technology, China
The nano-silver/Mg-Al hydrotalcite functional coating was prepared onto magnesium alloy by one-step hydrothermal reaction for improving its antibacterial and degrading behaviors.The results show that the nano silver particles and hydrotalcite coating were in-situ formed from the alloy surface during the reacting process. Additionally, the pH variation and antimicrobial test reveal that the fabricated coating can effectively suppress the degradation of the matrix and significantly inhibit the proliferation of Escherichia coli and Staphylococcus aureus, which is with great potential to improve functionality and corrosion resistance of biomedical magnesium alloy.
Surface modification of FeMnC alloy by oxygen and nitrogen plasma immersion ion implantation
* Letícia Andrade, Laval University - Laboratory for Biomaterials and Bioengineering (LBB), Canada
Carlo Paternoster, Laval University - Laboratory for Biomaterials and Bioengineering (LBB), Canada
Pascale Chevallier, Laval University - Laboratory for Biomaterials and Bioengineering (LBB), Canada
Diego Mantovani, Laval University - Laboratory for Biomaterials and Bioengineering (LBB), Canada
For confidentiality reasons and unpublished results contained, the presentation is not available online anymore. However, should the abstract be of your interest, please feel free to contact firstname.lastname@example.org and we will put you in contact with the authors. Plasma immersion ion implantation is a versatile technique to modify complex shapes devices such as medical implants. Regarding the importance of a degradable device to respond in a biocompatible and stable way, chemical composition and corrosion behaviour of the surface have to be modulate in order to provide a predictable response during a remodelling period in vivo. In this work the influence of surface modification of Fe-13Mn-1.2C after plasma implantation was discussed. The chemical groups implanted at the surface alter surface properties such as roughness and wettability modelling a controllable capacity to modify this type of substrate.
First assays with Fe-5%Mg milled powder as reinforcing phase of PLLA matrix composite
Marcela Lieblich, Centro Superior de Investigaciones Ciéntíficas
* Marta Multigner, Universidad Rey Juan Carlos, Spain
Marta Muñoz, Universidad Rey Juan Carlos, Spain
Joaquín Rams, Universidad Rey Juan Carlos, Spain
Jose Luis González-Carrasco, Consejo Superior de Investigaciones Científicas, Spain
In this work we propose the use of Fe-5%Mg as alternative reinforcement of PLLA. Fe has higher mechanical properties than Mg but lower degradation rates. Fe-Mg milled powder degrades faster than commercial Fe powder 2. Fe-5%Mg is compared with pure Mg and milled Fe to differentiate between the effect of milling from the effect of Mg. Degradation behaviour of composite materials was studied for 3 and 14 days of immersion in Hanks' solution in triplicate for each composition. Mass variation, water intake, compression tests and scanning electron microscopy (SEM) studies have been performed to analyse the degradation process.
Development of a novel Mg10Zn4Y/PLA scaffold for tissue engineering application
* Shweta Singh, IIT Delhi, India
Alok Srivastava, IIT Delhi, India
Pooja Bhati, IIT Delhi, India
Naresh Bhatnagar, IIT Delhi, India
Rapid degradation of magnesium and its alloys inside a human body poses a big challenge for bioresorbable tissue engineering applications. To address this, a novel porous bioresorbable composite of magnesium alloy (Mg-10wt.%Zn -4 wt.%Y) -60 wt. % with Polylactic acid (PLA)-40 wt. % is developed by utilizing the concept of solvent casting and salt leaching approach. Alloying with Yttrium and Zinc improves the strength, oxidization as well as ensures slow degradation of Mg10Zn4Y-microparticles in a physiological media. PLA provides a deep protective layer for Mg alloy and hence significantly reduces the corrosion rate. Mechanical study, microstructural characterization, degradation study and cell adhesion studies were performed on the fabricated porous Mg10Zn4Y/PLA composite structure.
Microstructure and mechanical characterization of binary MgCa, MgZn alloys and ternary MgZnCa alloys processed by Powder Metallurgy
* Sandra Cifuentes, Universidad Carlos III de Madrid, Spain
Marcela Lieblich, National Center for Metallurgical Research (CENIM-CSIC), Spain
Cristian Pastor, National Center for Metallurgical Research (CENIM-CSIC), Spain
Sophia Tsipas, Universidad Carlos III de Madrid, Spain
Magnesium possesses exceptional mechanical and physiological features that make it attractive for bone repair. The design of alloys intended to repair bone fractures includes the incorporation of biologically important elements like Ca and Zn. Binary alloys MgCa, MgZn and ternary alloys MgZnCa, have been thoroughly studied and show slower corrosion rate and good biocompatibility1,2. However, forming Mg alloys is difficult given its crystal structure and the limited availability of commercial alloys. Powder metallurgy can be used to mitigate the formability problem through near-net-shape processing and unique chemical compositions. In this work, we investigate the microstructure and mechanical properties of MgCa, MgZn and MgZnCa alloys processed using the route of powder blending and controlled atmosphere sintering.
Electrochemical evaluation of TiO2 coatings deposited on biodegradable MgZnCa alloy
* Benjamin Millan, Instituto de Investigaciones en Materiales, UNAM, Mexico
Jose Victoria-Hernandez, Helmholtz Zentrum Geesthacht, Germany
Gerrit Kurz, Helmholtz-Zentrum Geesthacht, Germany
Dietmar Letzig, Helmholtz-Zentrum Geesthacht, Germany
Sandra Rodil, Instituto de Investigaciones en Materiales, UNAM, Mexico
Biodegradable Mg based alloys are suitable for orthopedic applications due to their excellent mechanical properties and biocompatibility. Nevertheless, the main limitation of Mg alloys in human body fluid is its high corrosion rate mainly in the initial stage of implantation, which is distinguished by the high production of H2 bubbles and pH changes that lead to cytotoxic effects. Titanium dioxide coatings deposited are an interesting potential solution since they present good biocompatibility, improved osteoinduction and osteoconduction. However, the response can be different for amorphous (aTiO2) or nanocrystalline (cTiO2) coatings. Therefore, in this work, we evaluated the electrochemical response of a MgZnCa alloy coated with thin aTiO2 and cTiO2 films deposited using magnetron sputtering.
Biodegradable Zn-Mg alloys for stenting applications: in vitro biocompatibility and antibacterial activity
Topic: In Vitro
* Laura Catalina Córdoba Román, Institute for Bioengineering of Catalonia, Spain
Claudia García Mintegui, Biomaterials, Biomechanics and Tissue Engineering Group
Andrea Marquina, Biomaterials, Biomechanics and Tissue Engineering Group
Maria Pau Ginebra, Biomaterials, Biomechanics and Tissue Engineering Group
Marta Pegueroles, Biomaterials, Biomechanics and Tissue Engineering Group
For confidentiality reasons and unpublished results contained, the presentation is not available online anymore. However, should the abstract be of your interest, please feel free to contact email@example.com and we will put you in contact with the authors. In recent years, endovascular stenting research has been focusing on biodegradable metals since they potentially overcome the inherent limitations of bare-metal and drug-eluting stents by providing temporary support to the vessel wall1. Herein, we characterize the in vitro biocompatibility and the antibacterial activity of Zn-Mg alloys for stenting applications. Albumin coatings are also proposed to tune biodegradation to the required levels and for improved biocompatibility.
Study of the biocompatibility of combined PEO/sol-gel coatings on AZ31 magnesium substrates for biomedical applications
Topic: In Vitro
* Juan Pablo Fernández-Hernán, Universidad Rey Juan Carlos, Spain
Antonio Julio López, Universidad Rey Juan Carlos, Spain
Belén Torres, Universidad Rey Juan Carlos, Spain
Joaquín Rams, Universidad Rey Juan Carlos, Spain
Enrique Martínez-Campos, ICTP-CSIC, Spain
Endzhe Matykina, Universidad Complutense
The in-vitro biocompatibility of a combination of different coatings, obtained by plasma electrolytic oxidation (PEO) and sol-gel (SG), has been assessed. These coatings were used to control the degradation rate of AZ31 magnesium substrates used for biomedical applications. Five coating configurations were studied: one single PEO coating, two single SG coatings, with and without graphene nanoplatelets, and two multilayer PEO/SG coatings, with and without graphene nanoplatelets.
Influence of glucose on the degradation of PLA and PLA10Mg films
Topic: In Vitro
* Amparo M. Gallardo-Moreno, University of Extremadura, Spain
Verónica Luque-Agudo, University of Extremadura, Spain
M. Luisa González-Martín, University of Extremadura, Spain
PLA and PLA10Mg films will be exposed to diabetic conditions to check the influence of high levels of glucose in the degradation of these biomaterials. Hydrophobicity and topography will be the parameters monitored during the study.