Development of a Ta/TaN/TaNx(Ag)y/TaN nanocomposite coating system and bio-response study for biomedical applications

[EN] TaN(Ag) composited coatings are being investigated to improve biocompatibility of different biomedical devices due to the mechanical and chemical stability of TaN and bactericidal effect of silver nanoparticles. However, controlling the size, density, shape and especially the release of silver ions (Ag) into the surrounding medium becomes a challenge, since elevated levels of Ag could be cytotoxic. The aim of this work is to design and develop a new Ta/TaN/TaNx(Ag)y/TaN coating system, deposited by unbalanced DC magnetron sputtering technique, presenting an adequate balance between biocompatibility and bactericidal effect for potential applications in biomedical field. For this purpose, four different coating systems were deposited on 316 L stainless steel and silicon (100) samples applying a bias voltage of ¿30, ¿60, ¿90 and ¿120 V during the deposition of the top layer of TaN to vary its density. This manufacturing strategy allowed controlling the diffusion of silver nanoparticles to the coating surface and the release kinetics of silver ions in simulated body fluid (SBF). Biologic characterization has been performed with MC3T3-E1 pre-osteoblastic cells in terms of cell adhesion and long-term differentiation. Additionally, the adhesion and biofilm formation of the bacteria Streptococcus sanguinis strain in the deposited coating systems of Ta/TaN/TaNx(Ag)y/TaN were analyzed. The results indicated an improvement of cell adhesion and differentiation of the composited coating deposited with a bias of ¿30 V compared to other coatings. Concordantly, this coating showed the lowest bacterial adhesion and biofilm formation, representing an attractive and suitable composited material for biomedical applications.The technical support from the Spanish Ministry of Economy and Competitiveness (MINECO) (through the MAT2015-69315-C3-1-R) and FEDER funds project are acknowledged. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Echavarria, AM.; Rico Tortosa, PM.; Gómez Ribelles, JL.; Pacha-Olivenza, MA.; Fernandez-Calderon, M.; Bejarano-G, G. (2017). Development of a Ta/TaN/TaNx(Ag)y/TaN nanocomposite coating system and bio-response study for biomedical applications. Vacuum. 145:55-67. https://doi.org/10.1016/j.vacuum.2017.08.020S556714

Dynamic Adhesive Behavior and Biofilm Formation of <i>Staphylococcus aureus</i> on Polylactic Acid Surfaces in Diabetic Environments

Interest in biodegradable implants has focused attention on the resorbable polymer polylactic acid. However, the risk of these materials promoting infection, especially in patients with existing pathologies, needs to be monitored. The enrichment of a bacterial adhesion medium with compounds that are associated with human pathologies can help in understanding how these components affect the development of infectious processes. Specifically, this work evaluates the influence of glucose and ketone bodies (in a diabetic context) on the adhesion dynamics of S. aureus to the biomaterial polylactic acid, employing different approaches and discussing the results based on the physical properties of the bacterial surface and its metabolic activity. The combination of ketoacidosis and hyperglycemia (GK2) appears to be the worst scenario: this system promotes a state of continuous bacterial colonization over time, suppressing the stationary phase of adhesion and strengthening the attachment of bacteria to the surface. In addition, these supplements cause a significant increase in the metabolic activity of the bacteria. Compared to non-enriched media, biofilm formation doubles under ketoacidosis conditions, while in the planktonic state, it is glucose that triggers metabolic activity, which is practically suppressed when only ketone components are present. Both information must be complementary to understand what can happen in a real system, where planktonic bacteria are the ones that initially colonize a surface, and, subsequently, these attached bacteria end up forming a biofilm. This information highlights the need for good monitoring of diabetic patients, especially if they use an implanted device made of PLA

Enhanced Antibacterial Capability and Corrosion Resistance of Ti6Al4V Implant Coated with ZrO2/Organosilica Nanocomposite Sol-Gel Films

Ti6Al4V is one of the most commonly used biomaterials in orthopedic applications due to its interesting mechanical properties, corrosion resistance and reasonable biocompatibility, which derive from a compact, thin, and chemically stable oxide film that spontaneously develops on these materials surface able to minimize ion release. Despite these advantages, a post-operative serious and unresolved problem leading to the failure of the implant is the appearance of implant-associated infections. For this reason, the ability to control microbial adhesion is of importance in healthcare, particularly in modern surgery where postoperative implant associated infections are still an unresolved and serious complication. As a proof of concept, we have assessed the antibacterial behaviour of Ti6Al4V surfaces modified by organic-inorganic hybrid sol-gel films with different loading of ZrO2 nanoparticles. The starting organosilica sol was prepared using a mixture of γ-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethyl orthosilicate (TMOS). Tetrabutoxyzirconium (TBZ) was used as precursor of ZrO2 nanoparticles. Sol-gel films with variable contents of TBZ (0.2—1.0 wt.%) have been tested. The thermal stability of the resulting sol-gel films was studied by using thermal analysis (TG/DTG). Structural characterization of the films was carried out using Attenuated Total Reflectance Fourier transformer Infrared spectroscopy (ATR-FTIR). Surface morphology and composition of coated samples have been analized by Optical and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (OM and SEM/EDX) both before and after the corrosion tests were carried out. The evaluation of the barrier properties on the films and corrosion behaviour of the Ti6Al4V were carried out using Global and Local Electrochemical Impedance Spectroscopy (EIS/LEIS) during immersion in a simulated body fluid (SBF). Regarding bacterial adhesion, two representative strains of the vast majority of nosocomial infections related to orthopedic implants, i.e., Staphylococcus aureus and Staphylococcus epidermidis, were used. Optical and scanning electron microscopies observations have shown the formation of a uniform, homogeneous, crack free and highly adherent protective film on the Ti6Al4V substrates. The electrochemical studies and bacterial adhesion assessments have shown that the incorporation of ZrO2 in MAPTMS/TMOS matrix of the sol-gel films enhance their corrosion protection behaviour and antibacterial capability. Studies on the optimization of the sol-gel formulation to obtain the films with the best antibacterial capability without compromising their good corrosion resistance using different ZrO2 doses are in progress.MAT2015-65445-C2-1-R; MAT2015-63974-C4-3; M-ERA.NET PCIN-2016-146; IB16117; TE-0016-18; GR15089No data 2019UE

Decrease of Staphylococcal adhesion on surgical stainless steel after Si ion implantation

316LVM austenitic stainless steel is often the material of choice on temporal musculoskeletal implants and surgical tools as it combines good mechanical properties and acceptable corrosion resistance to the physiologic media, being additionally relatively inexpensive. This study has aimed at improving the resistance to bacterial colonization of this surgical stainless steel, without compromising its biocompatibility and resistance. To achieve this aim, the effect of Si ion implantation on 316LVM has been studied. First, the effect of the ion implantation parameters (50 keV; fluence: 2.5-5 × 10 16 ions/cm 2 ; angle of incidence: 45-90°) has been assessed in terms of depth profiling of chemical composition by XPS and nano-topography evaluation by AFM. The in vitro biocompatibility of the alloy has been evaluated with human mesenchymal stem cells. Finally, bacterial adhesion of Staphylococcus epidermidis and Staphylococcus aureus on these surfaces has been assessed. Reduction of bacterial adhesion on Si implanted 316LVM is dependent on the implantation conditions as well as the features of the bacterial strains, offering a promising implantable biomaterial in terms of biocompatibility, mechanical properties and resistance to bacterial colonization. The effects of surface composition and nano-topography on bacterial adhesion, directly related to ion implantation conditions, are also discussed.The work was supported by the Spanish Ministry for Science and Innovation Grants CIT-420000-2008-17 , MAT2009-14695-C04-01-02-03 and grants from Fundación Mutua Madrileña (Spain) , and the Junta de Extremadura-FEDER (Grant GR10149 ). NV is supported by Program I2 from Comunidad de Madrid (Spain) . A. Asenjo, from ICMM-CSIC , and J.A. Jiménez, from X-R Difraction Laboratory of CENIM-CSIC are acknowledged by the MFM and X-Ray analysis, respectively.Peer reviewe