Caracterización y respuesta antibacteriana de la superficie del biomaterial TI6AL4V sometido a diferentes modificaciones físicas

Las infecciones asociadas a dispositivos artificiales implantados en el organismo humano, como las prótesis osteoarticulares, suponen un serio problema en la actualidad. En su mayoría, estas infecciones están producidas por especies del género Staphylococcus. Estas bacterias se adhieren a la superficie de los biomateriales y pueden llegar a formar una biocapa que las protege tanto de las defensas del hospedador como del tratamiento antimicrobiano. Este modo peculiar de crecimiento de las bacterias dentro de biocapas tiene como consecuencia el desarrollo de un proceso infeccioso de naturaleza crónica que hace necesario, en ocasiones, la eliminación del dispositivo artificial para solucionar el problema, con los consiguientes costes humanos y económicos que ello puede conllevar. En el proceso de adhesión están implicadas la superficie de la bacteria y la del biomaterial y, aunque en principio ambas podrían considerarse como susceptibles de ser modificadas, la superficie del biomaterial es sobre la que podemos actuar directamente de forma controlada para condicionar el proceso y evitar en lo posible la adhesión inicial de los microorganismos y, por consiguiente, la posterior formación de biocapas. En este sentido, en los últimos años se están desarrollando técnicas de modificación superficial encaminadas a obtener nuevos acabados para implantes y prótesis para dotarlos de propiedades optimizadas frente a la adhesión bacteriana, respecto a las del material base. Bajo esta perspectiva, el objetivo concreto de esta tesis será la caracterización físico-química de las superficies de biomateriales metálicos de uso común en la fabricación de implantes, modificadas con diferentes tratamientos, y el estudio, mediante técnicas in vitro, del efecto de estas modificaciones sobre la afinidad de algunas cepas del género Staphylococcus a estos biomateriales, para así contribuir a la prevención de infecciones relacionadas con dispositivos metálicos osteoarticulares.Nowdays infections associated with artificial devices implanted in the human body, such as joint prostheses, are a serious problem. Most of these infections are caused by Staphylococcus spp. These bacteria adhere to the surface of biomaterials and may form a biofilm that protects bacteria from both host defenses and antimicrobial therapy. This peculiar mode of bacterial growth in biofilms results in the development of an infection of a chronic nature which sometimes yield to the replacement of the artificial device to solve the problem, resulting in human and economic costs. The surfaces of the bacteria and the biomaterial are involved in any adhesion process and, although both of them are able of being modified, researchers can directly modify the biomaterial surface for preventing the initial adhesion step and further biofilm formation. Consequently, the last years have led to the development of a range of surface modification techniques with the aim of obtaining new surface finishing with optimized properties against bacterial adhesion, in respect to the bulk material. Therefore the specific aim of this thesis will be the physico-chemical surface characterization of metallic biomaterials, commonly used in implants, subjected to different surface modifications and the study through different in vitro techniques of the affinity of some strains of Staphylococcus to these biomaterials, contributing to the prevention of infections associated with orthopedic metal devices

Bactericidal effect of magnesium ions over planktonic and sessile Staphylococcus epidermidis and Escherichia coli

Magnesium and its alloys are in focus to produce implants due to their excellent mechanical properties, facility to decompose in the body, enhancement of new bone formation and antibacterial properties. However, there is still a lack of consensus about the origin of such antibacterial effect. Up to date, most antibacterial studies were performed over newly synthesized MgO particles, nanotubes or nanowires in the form of slurries, integrated within polymeric matrixes or as coatings of other bulk materials whereas the effect of pure Mg2+ions over bacteria viability, in the absence of secondary processes, has not been assessed yet. Hence, in this study, we have characterized the bactericidal effect of Mg2+ions over two different bacteria strains, Staphylococcus epidermidis (Gram-positive) and Escherichia coli (Gram-negative) controlling both pH and ion concentration. Also, we have considered the ion effect on dissimilar planktonic and sessile cells on surfaces with different hydrophobicity

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

Structure, morphology, adhesion and in vitro biological evaluation of antibacterial multi-layer HA-Ag/SiO2/TiN/Ti coatings obtained by RF magnetron sputtering for biomedical applications

[EN] Biocompatible and antibacterial multi-layer coatings of hydroxyapatite (HA)-Ag/SiO2/TiN/Ti were obtained on the Ti-6Al-4V alloy, by means of the magnetron sputtering technique. During characterization of the coatings, the chemical composition was evaluated by energy dispersive X-ray spectroscopy and the phase analysis was carried out by X-ray diffraction. The morphology of the coatings was observed by field emission scanning electron microscopy, while transmission electron microscopy was used to appreciate their structure. The adhesion of the coatings to the substrate was evaluated by micro scratch test. The in vitro biological response was evaluated in terms of cytotoxicity, adhesion and differentiation of mouse mesenchymal stem cells, as well as adhesion and bacterial viability of Staphylococcus aureus strain. Through the compositional study carried out, the deposition of the HA phase was verified, with a Ca/P ratio close to 1.67 and the characteristic diffraction peaks of this compound. The structural study of the coatings evidenced the obtention of multi-layer architectures. The use of an intermediate SiO2/TiN/Ti trilayer was found to improve adhesion between HA-Ag and the substrate by 84%. Finally, the in vitro biological tests carried out indicated a potentially non-toxic character in the coatings. Additionally, an antibacterial effect was registered at low concentrations of Ag (3.0.co;2-3Lalueza, P., Monzón, M., Arruebo, M., & Santamaría, J. (2011). Bactericidal effects of different silver-containing materials. Materials Research Bulletin, 46(11), 2070-2076. doi:10.1016/j.materresbull.2011.06.041Peetsch, A., Greulich, C., Braun, D., Stroetges, C., Rehage, H., Siebers, B., … Epple, M. (2013). Silver-doped calcium phosphate nanoparticles: Synthesis, characterization, and toxic effects toward mammalian and prokaryotic cells. Colloids and Surfaces B: Biointerfaces, 102, 724-729. doi:10.1016/j.colsurfb.2012.09.040Yanovska, A. A., Stanislavov, A. S., Sukhodub, L. B., Kuznetsov, V. N., Illiashenko, V. Y., Danilchenko, S. N., & Sukhodub, L. F. (2014). Silver-doped hydroxyapatite coatings formed on Ti–6Al–4V substrates and their characterization. Materials Science and Engineering: C, 36, 215-220. doi:10.1016/j.msec.2013.12.011DeVasConCellos, P., Bose, S., Beyenal, H., Bandyopadhyay, A., & Zirkle, L. G. (2012). Antimicrobial particulate silver coatings on stainless steel implants for fracture management. Materials Science and Engineering: C, 32(5), 1112-1120. doi:10.1016/j.msec.2012.02.020VALLETREGI, M. (2004). Calcium phosphates as substitution of bone tissues. Progress in Solid State Chemistry, 32(1-2), 1-31. doi:10.1016/j.progsolidstchem.2004.07.001Surmenev, R. A., Surmeneva, M. A., Evdokimov, K. E., Pichugin, V. F., Peitsch, T., & Epple, M. (2011). The influence of the deposition parameters on the properties of an rf-magnetron-deposited nanostructured calcium phosphate coating and a possible growth mechanism. Surface and Coatings Technology, 205(12), 3600-3606. doi:10.1016/j.surfcoat.2010.12.039Surmeneva, M. A., Sharonova, A. A., Chernousova, S., Prymak, O., Loza, K., Tkachev, M. S., … Surmenev, R. A. (2017). Incorporation of silver nanoparticles into magnetron-sputtered calcium phosphate layers on titanium as an antibacterial coating. Colloids and Surfaces B: Biointerfaces, 156, 104-113. doi:10.1016/j.colsurfb.2017.05.016Mohseni, E., Zalnezhad, E., Bushroa, A. R., Abdel Magid Hamouda, Goh, B. T., & Yoon, G. H. (2015). Ti/TiN/HA coating on Ti–6Al–4V for biomedical applications. Ceramics International, 41(10), 14447-14457. doi:10.1016/j.ceramint.2015.07.081Ghasemi, S., Shanaghi, A., & Chu, P. K. (2017). Nano mechanical and wear properties of multi-layer Ti/TiN coatings deposited on Al 7075 by high-vacuum magnetron sputtering. Thin Solid Films, 638, 96-104. doi:10.1016/j.tsf.2017.07.049Hamdi, D. A., Jiang, Z.-T., No, K., Rahman, M. M., Lee, P.-C., Truc, L. N. T., … Dlugogorski, B. Z. (2019). Biocompatibility study of multi-layered hydroxyapatite coatings synthesized on Ti-6Al-4V alloys by RF magnetron sputtering for prosthetic-orthopaedic implant applications. Applied Surface Science, 463, 292-299. doi:10.1016/j.apsusc.2018.08.157Qi, J., Yang, Y., Zhou, M., Chen, Z., & Chen, K. (2019). Effect of transition layer on the performance of hydroxyapatite/titanium nitride coating developed on Ti-6Al-4V alloy by magnetron sputtering. Ceramics International, 45(4), 4863-4869. doi:10.1016/j.ceramint.2018.11.183Lenis, J. A., Hurtado, F. M., Gómez, M. A., & Bolívar, F. J. (2019). Effect of thermal treatment on structure, phase and mechanical properties of hydroxyapatite thin films grown by RF magnetron sputtering. Thin Solid Films, 669, 571-578. doi:10.1016/j.tsf.2018.11.045Lenis, J. A., Gómez, M. A., & Bolívar, F. J. (2019). Effect of deposition temperature and target-substrate distance on the structure, phases, mechanical and tribological properties of multi-layer HA-Ag coatings obtained by RF magnetron sputtering. Surface and Coatings Technology, 378, 124936. doi:10.1016/j.surfcoat.2019.124936Sofronia, A. M., Baies, R., Anghel, E. M., Marinescu, C. A., & Tanasescu, S. (2014). Thermal and structural characterization of synthetic and natural nanocrystalline hydroxyapatite. Materials Science and Engineering: C, 43, 153-163. doi:10.1016/j.msec.2014.07.023Lenis, J. A., Bejarano, G., Rico, P., Ribelles, J. L. G., & Bolívar, F. J. (2019). Development of multilayer Hydroxyapatite - Ag/TiN-Ti coatings deposited by radio frequency magnetron sputtering with potential application in the biomedical field. Surface and Coatings Technology, 377, 124856. doi:10.1016/j.surfcoat.2019.06.097Lenis, J. A., Toro, L. J., & Bolívar, F. J. (2019). Multi-layer bactericidal silver - calcium phosphate coatings obtained by RF magnetron sputtering. Surface and Coatings Technology, 367, 203-211. doi:10.1016/j.surfcoat.2019.03.038Valverde, A., Pérez-Álvarez, L., Ruiz-Rubio, L., Pacha Olivenza, M. A., García Blanco, M. B., Díaz-Fuentes, M., & Vilas-Vilela, J. L. (2019). Antibacterial hyaluronic acid/chitosan multilayers onto smooth and micropatterned titanium surfaces. Carbohydrate Polymers, 207, 824-833. doi:10.1016/j.carbpol.2018.12.039Surmeneva, M. A., Chaikina, M. V., Zaikovskiy, V. I., Pichugin, V. F., Buck, V., Prymak, O., … Surmenev, R. A. (2013). The structure of an RF-magnetron sputter-deposited silicate-containing hydroxyapatite-based coating investigated by high-resolution techniques. Surface and Coatings Technology, 218, 39-46. doi:10.1016/j.surfcoat.2012.12.023Nelea, V., Morosanu, C., Iliescu, M., & Mihailescu, I. N. (2003). Microstructure and mechanical properties of hydroxyapatite thin films grown by RF magnetron sputtering. Surface and Coatings Technology, 173(2-3), 315-322. doi:10.1016/s0257-8972(03)00729-1Ding, S.-J., Ju, C.-P., & Lin, J.-H. C. (1999). Characterization of hydroxyapatite and titanium coatings sputtered on Ti-6Al-4V substrate. Journal of Biomedical Materials Research, 44(3), 266-279. doi:10.1002/(sici)1097-4636(19990305)44:33.0.co;2-4Ivanova, A. A., Surmeneva, M. A., Tyurin, A. I., Pirozhkova, T. S., Shuvarin, I. A., Prymak, O., … Surmenev, R. A. (2016). Fabrication and physico-mechanical properties of thin magnetron sputter deposited silver-containing hydroxyapatite films. Applied Surface Science, 360, 929-935. doi:10.1016/j.apsusc.2015.11.087Contreras Romero, E., Cortínez Osorio, J., Talamantes Soto, R., Hurtado Macías, A., & Gómez Botero, M. (2019). Microstructure, mechanical and tribological performance of nanostructured TiAlTaN-(TiAlN/TaN)n coatings: Understanding the effect of quaternary/multilayer volume fraction. Surface and Coatings Technology, 377, 124875. doi:10.1016/j.surfcoat.2019.07.086Deligianni, D. (2001). Effect of surface roughness of the titanium alloy Ti–6Al–4V on human bone marrow cell response and on protein adsorption. Biomaterials, 22(11), 1241-1251. doi:10.1016/s0142-9612(00)00274-xZareidoost, A., Yousefpour, M., Ghaseme, B., & Amanzadeh, A. (2012). The relationship of surface roughness and cell response of chemical surface modification of titanium. Journal of Materials Science: Materials in Medicine, 23(6), 1479-1488. doi:10.1007/s10856-012-4611-9Surmeneva, M. A., Tyurin, A. I., Mukhametkaliyev, T. M., Pirozhkova, T. S., Shuvarin, I. A., Syrtanov, M. S., & Surmenev, R. A. (2015). Enhancement of the mechanical properties of AZ31 magnesium alloy via nanostructured hydroxyapatite thin films fabricated via radio-frequency magnetron sputtering. Journal of the Mechanical Behavior of Biomedical Materials, 46, 127-136. doi:10.1016/j.jmbbm.2015.02.025Quirama, A., Echavarría, A. M., Meza, J. M., Osorio, J., & Bejarano G, G. (2017). Improvement of the mechanical behavior of the calcium phosphate coatings deposited onto Ti6Al4V alloy using an intermediate TiN/TiO2 bilayer. Vacuum, 146, 22-30. doi:10.1016/j.vacuum.2017.09.024Surmeneva, M. A., Kleinhans, C., Vacun, G., Kluger, P. J., Schönhaar, V., Müller, M., … Surmenev, R. A. (2015). Nano-hydroxyapatite-coated metal-ceramic composite of iron-tricalcium phosphate: Improving the surface wettability, adhesion and proliferation of mesenchymal stem cells in vitro. Colloids and Surfaces B: Biointerfaces, 135, 386-393. doi:10.1016/j.colsurfb.2015.07.057Chen, Y., Zheng, X., Xie, Y., Ji, H., Ding, C., Li, H., & Dai, K. (2010). Silver release from silver-containing hydroxyapatite coatings. Surface and Coatings Technology, 205(7), 1892-1896. doi:10.1016/j.surfcoat.2010.08.073Actis, L., Gaviria, L., Guda, T., & Ong, J. L. (2013). Antimicrobial surfaces for craniofacial implants: state of the art. Journal of the Korean Association of Oral and Maxillofacial Surgeons, 39(2), 43. doi:10.5125/jkaoms.2013.39.2.43Parvizi, J., Aggarwal, V., & Rasouli, M. (2013). Periprosthetic joint infection: Current concept. Indian Journal of Orthopaedics, 47(1), 10. doi:10.4103/0019-5413.106884Redey, S. A., Nardin, M., Bernache-Assolant, D., Rey, C., Delannoy, P., Sedel, L., & Marie, P. J. (2000). Behavior of human osteoblastic cells on stoichiometric hydroxyapatite and type A carbonate apatite: Role of surface energy. Journal of Biomedical Materials Research, 50(3), 353-364. doi:10.1002/(sici)1097-4636(20000605)50:33.0.co;2-cSpriano, S., Bosetti, M., Bronzoni, M., Vernè, E., Maina, G., Bergo, V., & Cannas, M. (2005). Surface properties and cell response of low metal ion release Ti-6Al-7Nb alloy after multi-step chemical and thermal treatments. Biomaterials, 26(11), 1219-1229. doi:10.1016/j.biomaterials.2004.04.026Vogler, E. A. (1999). Water and the acute biological response to surfaces. Journal of Biomaterials Science, Polymer Edition, 10(10), 1015-1045. doi:10.1163/156856299x00667Lim, J. Y., Liu, X., Vogler, E. A., & Donahue, H. J. (2004). Systematic variation in osteoblast adhesion and phenotype with substratum surface characteristics. Journal of Biomedical Materials Research, 68A(3), 504-512. doi:10.1002/jbm.a.20087Sengstock, C., Diendorf, J., Epple, M., Schildhauer, T. A., & Köller, M. (2014). Effect of silver nanoparticles on human mesenchymal stem cell differentiation. Beilstein Journal of Nanotechnology, 5, 2058-2069. doi:10.3762/bjnano.5.214Sahuquillo Arce, J. M., Iranzo Tatay, A., Llácer Luna, M., Sanchis Boix, Y., Guitán Deltell, J., González Barberá, E., … Gobernado Serrano, M. (2011). Estudio in vitro de las propiedades antimicrobianas de una espuma de poliuretano que libera iones de plata. Cirugía Española, 89(8), 532-538. doi:10.1016/j.ciresp.2011.02.015Jamuna-Thevi, K., Bakar, S. A., Ibrahim, S., Shahab, N., & Toff, M. R. M. (2011). Quantification of silver ion release, in vitro cytotoxicity and antibacterial properties of nanostuctured Ag doped TiO2 coatings on stainless steel deposited by RF magnetron sputtering. Vacuum, 86(3), 235-241. doi:10.1016/j.vacuum.2011.06.011Chernousova, S., & Epple, M. (2012). Silver as Antibacterial Agent: Ion, Nanoparticle, and Metal. Angewandte Chemie International Edition, 52(6), 1636-1653. doi:10.1002/anie.20120592

In vivo bactericidal efficacy of the Ti6Al4V surface after ultraviolet C treatment

FONDO Las infecciones asociadas con biomateriales son una de las complicaciones más importantes en la cirugía ortopédica. El objetivo principal de este estudio fue demostrar el efecto bactericida in vivo de la radiación ultravioleta (UV) en las superficies de Ti6Al4V. MATERIALES Y MÉTODO Se desarrolló un modelo experimental de infecciones relacionadas con dispositivos mediante la inoculación directa de Staphylococcus aureus en el canal de ambos fémures de 34 ratas. Un pin Ti6Al4V irradiado con radiación UV se ajustó a presión en el canal por inserción retrógrada en un fémur y el pin de control se insertó en el fémur contralateral. Para evaluar la eficacia de la radiación UV, se compararon los recuentos medios de colonias después de la inoculación en los sujetos experimentales y el grupo de control en diferentes momentos de sacrificio y en diferentes dosis de inóculo. RESULTADOS A las 72 h, los recuentos medios de colonias después de la inoculación en fémures experimentales fueron significativamente más bajos que los del grupo de control, con un porcentaje de reducción del 76% (p = 0,041). Una diferencia similar entre los pernos de control y experimentales se observó a las 24 h con una dosis de inóculo <104 unidades formadoras de colonias (UFC), para la cual el porcentaje de reducción fue de 70.48% (p = 0.017). CONCLUSIÓN La superficie irradiada de Ti6Al4V puede reducir la colonización bacteriana temprana de los pines de Ti6AlV ubicados en el canal medular y en el fémur circundante. Las reducciones dependen de los inóculos iniciales utilizados para causar la infección en los animales y los mayores efectos se detectan para los inóculos <104 UFC.BACKGROUND Biomaterial-associated infections are one of the most important complications in orthopedic surgery. The main goal of this study was to demonstrate the in vivo bactericidal effect of ultraviolet (UV) irradiation on Ti6Al4V surfaces. MATERIALS AND METHODS An experimental model of device-related infections was developed by direct inoculation of Staphylococcus aureus into the canal of both femurs of 34 rats. A UV-irradiated Ti6Al4V pin was press-fit into the canal by retrograde insertion in one femur and the control pin was inserted into the contralateral femur. To assess the efficacy of UV radiation, the mean colony counts after inoculation in the experimental subjects and the control group were compared at different times of sacrifice and at different inoculum doses. RESULTS At 72 h, the mean colony counts after inoculation in experimental femurs were significantly lower than those of the control group, with a reduction percentage of 76 % (p = 0.041). A similar difference between control and experimental pins was observed at 24 h using an inoculum dose <104 colony-forming units (CFU), for which the reduction percentage was 70.48 % (p = 0.017). CONCLUSION The irradiated surface of Ti6Al4V is able to reduce early bacterial colonization of Ti6AlV pins located in the medullar channel and in the surrounding femur. The reductions depend on the initial inoculums used to cause infection in the animals and the greatest effects are detected for inoculums <104 CFU.• Ministerio de Ciencia e Innovación. Beca MAT2009-14695-CO4- C01 • Junta de Extremadura. Beca GR10149 • Junta de Extremadura. Beca predoctoral para María Delgado RastrollopeerReviewe

Efficacy of laser shock processing of biodegradable Mg and Mg-1Zn alloy on their in vitro corrosion and bacterial response

Laser shock processing (LSP) is increasingly applied as an effective technology for improving the properties of different metallic components. This is done principally to enhance their corrosion and fatigue life behaviour, stress corrosion cracking resistance, etc. In this paper, LSP has been applied to a commercially pure Mg and a Mg-1Zn alloy (wt%) which is aimed to be used as a biodegradable material for biomedical applications. The rational for microalloying with Zn is not only influencing the bacterial response, but also enhancing corrosion resistance and mechanical strength of Mg without causing any toxic effect. The present work is focussed on the examination of the effects of the LSP treatment on the relevant surface related properties of the samples and their correlation with the surface and subsurface induced modifications such as residual stress state, microstructural, roughness, hardness, etc. Central to this investigation is the study of the corrosion response and antibacterial properties against Staphylococcus epidermidis of the different samples as a function of material and LSP parameters. The results show that the application of LSP introduces compressive residual stresses up to 1 mm deep. This occurs together with a significant improvement in corrosion resistance, and less bacterial colonization.Peer reviewe

Caracterización y respuesta antibacteriana de la superficie del biomaterial TI6AL4V sometido a diferentes modificaciones físicas

Las infecciones asociadas a dispositivos artificiales implantados en el organismo humano, como las prótesis osteoarticulares, suponen un serio problema en la actualidad. En su mayoría, estas infecciones están producidas por especies del género Staphylococcus. Estas bacterias se adhieren a la superficie de los biomateriales y pueden llegar a formar una biocapa que las protege tanto de las defensas del hospedador como del tratamiento antimicrobiano. Este modo peculiar de crecimiento de las bacterias dentro de biocapas tiene como consecuencia el desarrollo de un proceso infeccioso de naturaleza crónica que hace necesario, en ocasiones, la eliminación del dispositivo artificial para solucionar el problema, con los consiguientes costes humanos y económicos que ello puede conllevar. En el proceso de adhesión están implicadas la superficie de la bacteria y la del biomaterial y, aunque en principio ambas podrían considerarse como susceptibles de ser modificadas, la superficie del biomaterial es sobre la que podemos actuar directamente de forma controlada para condicionar el proceso y evitar en lo posible la adhesión inicial de los microorganismos y, por consiguiente, la posterior formación de biocapas. En este sentido, en los últimos años se están desarrollando técnicas de modificación superficial encaminadas a obtener nuevos acabados para implantes y prótesis para dotarlos de propiedades optimizadas frente a la adhesión bacteriana, respecto a las del material base. Bajo esta perspectiva, el objetivo concreto de esta tesis será la caracterización físico-química de las superficies de biomateriales metálicos de uso común en la fabricación de implantes, modificadas con diferentes tratamientos, y el estudio, mediante técnicas in vitro, del efecto de estas modificaciones sobre la afinidad de algunas cepas del género Staphylococcus a estos biomateriales, para así contribuir a la prevención de infecciones relacionadas con dispositivos metálicos osteoarticulares.Nowdays infections associated with artificial devices implanted in the human body, such as joint prostheses, are a serious problem. Most of these infections are caused by Staphylococcus spp. These bacteria adhere to the surface of biomaterials and may form a biofilm that protects bacteria from both host defenses and antimicrobial therapy. This peculiar mode of bacterial growth in biofilms results in the development of an infection of a chronic nature which sometimes yield to the replacement of the artificial device to solve the problem, resulting in human and economic costs. The surfaces of the bacteria and the biomaterial are involved in any adhesion process and, although both of them are able of being modified, researchers can directly modify the biomaterial surface for preventing the initial adhesion step and further biofilm formation. Consequently, the last years have led to the development of a range of surface modification techniques with the aim of obtaining new surface finishing with optimized properties against bacterial adhesion, in respect to the bulk material. Therefore the specific aim of this thesis will be the physico-chemical surface characterization of metallic biomaterials, commonly used in implants, subjected to different surface modifications and the study through different in vitro techniques of the affinity of some strains of Staphylococcus to these biomaterials, contributing to the prevention of infections associated with orthopedic metal devices

Si+ ion implantation reduces the bacterial accumulation on the Ti6Al4V surface under flow

Póster presentado al BIO-COAT: "Surface modification and functionalization of materials for biomedical applications" celebrado en Zaragoza el 24 de junio de 2010.-- Publicado como artículo en Journal of Physics: Conference Series 252(1): http://dx.doi.org/10.1088/1742-6596/252/1/012017MAT2006-27439-E (Ministerio de Ciencia e Innovación).Peer reviewe

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

236th ECS MeetingTi6Al4V 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 ¿-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

Relevance of Topographic Parameters on the Adhesion and Proliferation of Human Gingival Fibroblasts and Oral Bacterial Strains

Dental implantology allows replacement of failing teeth providing the patient with a general improvement of health. Unfortunately not all reconstructions succeed, as a consequence of the development of infections of bacterial origin on the implant surface. Surface topography is known to modulate a differential response to bacterial and mammalian cells but topographical measurements are often limited to vertical parameters. In this work we have extended the topographical measurements also to lateral and hybrid parameters of the five most representative implant and prosthetic component surfaces and correlated the results with bacterial and mammalian cell adhesion and proliferation outcomes. Primary human oral gingival fibroblast (gum cells) and the bacterial strains: Streptococcus mutans, Streptococcus sanguinis and Aggregatibacter actinomycetemcomitans, implicated in infectious processes in the oral/implant environment were employed in the presence or absence of human saliva. The results confirm that even though not all the measured surface is available for bacteria to adhere, the overall race for the surface between cells and bacteria is more favourable to the smoother surfaces (nitrided, as machined or lightly acid etched) than to the rougher ones (strong acid etched or sandblasted/acid etched)