RESUMEN
Titanium alloys are known to nucleate an apatite layer when in contact with simulated body fluid. This improves the bioactivity of titanium implants and accelerates osseointegration. Promoting the formation of hydroxyapatite on biocompatible metals is, therefore, a very important topic of biomaterials research. In this paper, the formation of hydroxyapatite (HA) on the near-beta Ti-13Nb-13Zr alloy by immersion in minimal essential medium (MEM), with and without H(2)O(2) addition, has been studied using electrochemicals methods, scanning electron microscopy and X-ray photoelectron spectroscopy. The in vitro biocompatibility of this alloy was evaluated by cytotoxicity tests. The Ti-13Nb-13Zr alloy exhibits passive behaviour over a wide potential range in MEM and the passive film is composed of an inner barrier layer and an outer porous layer. The addition of H(2)O(2) leads to a thickening of the outer porous layer and strongly reduced current density. With regard to the surface composition, immersion in MEM solution results in the formation of an island-like distribution of HA+amino acids. Addition of H(2)O(2) to the MEM solution strongly promotes the formation of a thicker, continuous but porous nanocomposite layer of HA+amino acids. The Ti-13Nb-13Zr alloy is non-toxic and the nanocomposite HA+amino acid layer formed in the MEM solution favours the growth of osteoblast cells. For Ti alloys, the release of H(2)O(2) in the anti-inflammatory response appears to be an important beneficial process as it accelerates osseointegration.
Asunto(s)
Materiales Biocompatibles/química , Nanocompuestos/química , Niobio/química , Titanio/química , Circonio/química , Aminoácidos/química , Células Cultivadas , Medios de Cultivo/química , Durapatita/química , Electroquímica/métodos , Humanos , Peróxido de Hidrógeno/química , Microscopía Electrónica de Rastreo/métodos , Porosidad , Titanio/metabolismoRESUMEN
In this study, the in vitro corrosion resistance of a superferritic stainless steel in naturally aerated Hank's solution at 37 degrees C has been determined to evaluate the steel for use as a biomaterial. The potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS) were used to determine the corrosion resistance. The polarization results showed very low current densities at the corrosion potential and electrochemical behavior typical of passive metals. At potentials above 0.75 V (SCE), and up to that of the oxygen evolution reaction, the superferritic steel exhibited transpassive behavior followed by secondary passivation. The superferritic stainless steel exhibited high pitting resistance in Hank's solution. This steel did not reveal pits even after polarization to 3000 mV (SCE). The EIS results indicated high impedance values at low frequencies, supporting the results obtained from the polarization measurements. The results obtained for the superferritic steel have been compared with those of the Ti-13Nb-13Zr alloy and an austenitic stainless steel, as Ti alloys are well known for their high corrosion resistance and biocompatibility, and the austenitic stainless steel is widely used as an implant material. The cytotoxicity tests indicated that the superferritic steel, the austenitic steel, and the Ti-13Nb-13Zr alloy were not toxic. Based on corrosion resistance and cytotoxicity results, the superferritic stainless steel can be considered as a potential biomaterial.
Asunto(s)
Materiales Biocompatibles/química , Soluciones Isotónicas/química , Acero Inoxidable/química , Titanio/farmacología , Aleaciones , Cromo/química , Corrosión , Impedancia Eléctrica , Electroquímica/métodos , Concentración de Iones de Hidrógeno , Técnicas In Vitro , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Oxígeno/química , Potenciometría , Análisis Espectral/métodos , Acero , Propiedades de Superficie , Temperatura , Resistencia a la Tracción , Factores de Tiempo , Titanio/químicaRESUMEN
BACKGROUND: Alopecia areata is a common disease and may be associated with autoimmune disease, atopy, Down syndrome, emotional stress, and foci of sepsis. METHODS: Seven cases of alopecia areata were diagnosed among workers in the Water and Effluent Treatment Sector (WETS) of a paper factory, representing a 0.6% incidence, when the value for the population at large is 0.1%. Three of these workers are assigned to the WETS on a permanent basis and four provide maintenance services. One of the latter patients had alopecia areata that fully regressed. Because biologic treatment of water and effluents involves saprophytic bacteria and fungi as well as chemical substances such as acrylamide, a clinical examination and laboratory tests were performed on all workers assigned permanently to the WETS (N = 9) and on 25% of the workers, selected at random providing services to the sector (N = 14). RESULTS: There was no association between alopecia areata and atopy, dermatophytosis, or bacteria isolated. Toxicologic evaluation revealed an acrylamide-like substance in 7 workers with alopecia areata, with a statistically significant correlation. Measures were taken at the workplace to decrease worker contact with the mists (probably containing acrylamide) in the pulp-pressing room; no other cases of alopecia areata had been detected 1 year after the study. CONCLUSIONS: A survey of the literature did not show reports of alopecia areata as an occupational dermatosis, but our conclusion is, that this dermatosis could be due to the professional activities of the workers at the paper factory studied.