Sol-gel coatings for protection and bioactivation of metals used in orthopaedic devices

The aim of this work is the production and characterisation of sol-gel coatings for protection and bioactivation of metals used as standard surgical implant materials, such as stainless steel 316 L (ASTM F138), Co based alloys (ASTM F75) and titanium alloy Ti-6A1-4V (ASTM F67). These films should both prevent degradation of the substrates by wear or corrosion, and bioactivate the material for inducing the formation of a hydroxyapatite (HA) rich layer onto the material surface, thereby permitting a natural bonding to living tissues. Formation of HA layers can be observed on performing in vitro tests by soaking the material in simulated body solutions. The work describes the development of coatings containing bioactive glass and glass-ceramic particles in hybrid methyl-triethoxysilane (MTES) and tetraethylorthosilicate (TEOS) acidic sol, applied by dip-coating to surgical alloys, AISI 316 L, ASTM F75 and ASTM 67, with the aim of accomplishing both high corrosion resistance of the metal in the body environment and adhesion of the implant to the surrounding tissue. The performance of the coated metal was evaluated in vitro by electrochemical techniques including potentiodynamic polarisation curves and electrochemical impedance spectroscopy, to follow the formation of hydroxyapatite on the surface, as well as the in vitro release of ions by plasma atomic emission spectroscopy (ICP-MS) after up to one year of immersion. In vivo behaviour was evaluated by subcutaneous tests and endomedullar implantation in Hokaido rats to study possible rejection reactions and natural bonding to living tissue.Peer Reviewe

SiO2-CaO-P2O5 (58S) sol gel glass applied onto surgical grade stainless steel by spray technique: morphological characterization by digital image processing

AISI 316L stainless steel is commonly used as a low-cost material for permanent implants. It can be protected for degradation and corrosion by applying a hybrid silica based coating. Also the bioactive response of the implant can only be achieved by functionalizing the coated implant surface. The aim of this work is to synthesize and characterize a sol-gel made glass particles from the system SiO2-CaO-P2O5 with potential as bone inductive material, with and without an aging treatment of the precursor solution. The glass was synthesized by sol-gel technique that, comparing with melt glasses, generates an open net structure that could lead to particle dissolution and apatite deposition for biological purposes. The synthesized glass is dispersed by spray onto AISI 316L protected by a hybrid silica based coating, generating deposits with different size and morphology. To characterize the particles composition, microRaman spectroscopy was applied. It showed that no significant changes were reached after aging or thermal treatment of the deposited particles. Image processing techniques based on Mathematical Morphology were used to analyze morphology and sizes of the deposits obtain with the different sols (aged and no aged). Aproximately 50% of the surface was covered with particles made with a glass aged, and a 25% of covered area was reached with no aged one. When no aged glass particles were deposited, the particle size distribution shows the presence of many big particles with a roundness factor between 0.8 and 1 in a high percentage, meaning that they are spherical due to the presence of solvent and with a more open glass structure in the no aged glass. The Digital Image Processing and Raman spectroscopy tools help to analyze, characterize and quantify the bioactive particles deposited onto coated surgical grade stainless steel in terms of morphology, distribution and composition

Evaluation of annealed titanium oxide nanotubes on titanium: From surface characterization to in vivo assays

The entire route from anodic oxidation and surface characterization, including in vitro experiments and finally in vivo osseointegration assays were performed with the aim to evaluate nanotubular and crystalline annealed titanium oxides as a suitable surface for grade 2 titanium permanent implants. Polished titanium (T0) was compared with anodized surfaces obtained in acidic media with fluoride, leading to an ordered nanotubular structure of titanium oxide on the metal surface, characterized by tube diameter of 89 ± 24 nm (Tnts). Samples were thermally treated in air (TntsTT) to increase the anatase crystalline phase on nanotubes, with minor alteration of the structure. Corrosion tests were performed to evaluate the electrochemical response after 1, 14, and 28 days of immersion in simulated body fluid. Based on the in vitro results, heat-treated titanium nanotubes (TntsTT) were selected as a promissory candidate to continue with the osseointegration in vivo assays. The in vivo results showed no major improvement in the osseointegration process when compared with untreated Ti after 30 days of implantation and there also was a lower increase in the development of new osseous tissue.Fil: Gomez Sanchez, Andrea Valeria. Universidad Tecnológica Nacional; ArgentinaFil: Katunar, María R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Pastore, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Científicas y Tecnológicas en Electrónica. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones Científicas y Tecnológicas en Electrónica; ArgentinaFil: Tano de la Hoz, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Ceré, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Bioactive coatings prepared by sol–gel on stainless steel 316L

This work describes the development and characterization of coatings obtained by the sol–gel technique, applied on stainless steel used in orthopaedic surgery. These coatings are applied to reduce metal corrosion and adverse reactions when implanted. Hybrid coatings of silica containing hydroxyapatite, bioactive glass and glass–ceramic particles were prepared and applied on metal substrates. The coated samples were further tested in vitro to study their electrochemical properties and bioactive response. The electrochemical properties were evaluated by means of potentiodynamic polarization assays using simulated body fluid (SBF) as electrolyte. In vitro bioactivity tests were performed by soaking the coated samples in SBF at 37 C with a ratio sample area/fluid volume of 0.35cm/ml for different periods. The coatings improve corrosion resistance of the steel substrate and in vitro tests revealed that all the films show signs of bioactivity.Peer reviewe

Dual-surface modification of titanium alloy with anodizing treatment and bioceramic particles for enhancing prosthetic devices

In this work, two strategies of surface modification of metallic biomedical implants are presented. An anodizing treatment onto titanium surface to enhance a barrier effect for minimizing corrosion and a bioactivation of the surface by the application of sol?gel coatings containing bioactive particles from the 45S5 Bioglass family doped with strontium was done. The substitution of calcium by strontium (Sr) generates a local controlled release of Sr-ion to the media. Strontium is known to reduce osteoclasts activity and stimulate bone formation. Surface analysis methods as micro-Raman spectroscopy, AC/DC electrochemical tests, X-ray diffraction and different microcopies were used for determining chemical reactions and integrity in simulated body fluid solution. The deposition and dispersion of the bioactive particles in the coatings were analyzed by digital image processing tools. The presence of apatite-related compounds was confirmed by the appearance of characteristic phosphate peak at 960 cm-1 (Raman). The integrity and protection of the coating were evaluated electrochemically. The applied coating system provided a good protection of the bare metal to the aggressive fluids, even after 30 days of immersion, where the dissolution of the bioactive particles without and with Sr, and deposition of phosphate-related compounds are taking place.Fil: Gonzalez Galdos, M. V.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Pastore, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Científicas y Tecnológicas En Electronica. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones Científicas y Tecnológicas En Electronica.; ArgentinaFil: Ballarre, J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Ceré, S. M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Platelet antiaggregants or anticoagulants in the secondary prevention after myocardial infarct

Platelet antiaggregants or anticoagulants in the secondary prevention after myocardial infarc