Browsing by Author "Multigner, M."
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Item Bacterial adhesion reduction on a biocompatible Si+ ion implanted austenitic stainless steel(2011-10-10) Gallardo-Moreno, A. M.; Multigner, M.; Calzado-Martín, A.; Méndez-Vilas, A.; Saldaña, L.; Galván, J. C.; Pacha-Olivenza, M. A.; Perera-Núñez, J.; González-Carrasco, J. L.; Braceras, I.; Vilaboa, N.; González-Martín, M. L.; INGENIERÍA DE SUPERFICIESThe colonization of an implant surface by bacteria is an extremely important medical problem, which often leads to the failure of medical devices. Modern surface modification techniques, such as ion implantation, can confer to the surfaces very different properties from those of the bulk underlying material. In this work, austenitic stainless steel 316 LVM has been superficially modified by Si+ ion implantation. The effect of surface modification on the biocompatibility and bacterial adhesion to 316 LVM stainless steel has been investigated. To this aim, human mesenchymal stem cells (hMSCs), as precursor of osteoblastic cells, and bacterial strains relevant in infections related to orthopedic implants, i.e., Staphylococcus aureus and Staphylococcus epidermidis, have been assayed. For the understanding of changes in the biological response associated to ion implantation, variations in the chemical surface composition, topography, surface Gibbs energy, isoelectric point and in vitro corrosion behavior have been evaluated. hMSCs adhesion, viability and differentiation to the osteoblastic lineage were unaffected by Si+ ion implantation. On the other hand, Si+ ion implantation diminished the number of attached bacteria in static conditions and led to smaller adhesion rates and retention strength. The ability of implanted surfaces to reduce the bacterial adhesion was higher for Staphylococcus epidermidis than for Staphylococcus aureus. This study proposes Si+ ion implantation as an effective way of reducing bacterial adhesion on 316 LVM stainless steel surfaces without compromising its good biocompatibility.Item In vitro corrosion behaviour of surgical 316LVM stainless steel modified by Si+ ion implantation – An electrochemical impedance spectroscopy study(2016-08-15) Galván, J.C.; Larrea, M.T.; Braceras, I.; Multigner, M.; González-Carrasco, J.L.; INGENIERÍA DE SUPERFICIESThis work deals with the surface modification of 316LVM stainless steel by Si+ ion implantation and the in vitro study of its effect on the short-term corrosion behaviour and ion release. In order to achieve a high Si content close to the surface, the experimental set up was designed with different implantation doses, acceleration voltages and angles of incidence. Corrosion tests were carried out by Electrochemical Impedance Spectroscopy (EIS). A special feature of this paper is the evaluation of the EIS data obtained through a critical analysis of the existing equivalent electrical circuits, in order to establish adequate parameters and scientific criteria to propose a classification of the corrosion response of the investigated surfaces. It has been demonstrated that doses of Si+ ion implantation equal to 2.5 × 1016 ion/cm2 and an acceleration voltages of 50 keV enhanced the corrosion protection. In contrast, higher ion-implantation dose (1 × 1017 ion/cm2) and acceleration voltage (80 keV) produced worse results, probably due to the development of strain induced α’-martensite. The quantity of relevant ions (Cr, Fe, Mn, Mo, Ni and Si) released to the medium was determined by an optimized Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) method. It has been shown that a better corrosion resistance is accompanied by a reduction in the amount of ions released.Item Roughening of metallic biomaterials by abrasiveless waterjet peening: Characterization and viability(2011-04-04) Barriuso, S.; Lieblich, M.; Multigner, M.; Etxeberria, I.; Alberdi, A.; González-Carrasco, J. L.; FABRIC_INTELThis study addresses the roughening of AISI 316 LVM and Ti6Al4V by waterjet peening (WJP) without abrasive particles, looking for rough surfaces free of embedded particles that could act as severe notches. Strong parameters have been selected to characterize and check viability of abrasiveless WJP; a water pressure of 360. MPa and two slow traverse velocities: 0.05 and 0.1. m/min. After processing, large number of pits with undercuts plus some larger intrusions are observed, which are more abundant and larger in the steel specimens and in those treated with the lower traverse speed. Cross sectional examination of 316 LVM reveals a significant grain size refinement in the subsurface zone, 10-20. μm wide, that exhibits a submicrometric/nanometric grain size, accompanied with a hardness gradient (50% increase) that extends to a depth of up to about 100. μm. The analysis of the magnetic hysteresis loops discards the presence of strain induced α-martensite. No hardness or microstructural gradient was developed in the Ti6Al4V alloy. The results indicate that in AISI 316 LVM the volume loss occurs through hardening of the subsurface, embrittlement, crack formation and erosion. In Ti6Al4V the material removal may take place first at the vanadium reach β-phase.