ABSTRACT
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.
Subject(s)
Biocompatible Materials/chemistry , Isotonic Solutions/chemistry , Stainless Steel/chemistry , Titanium/pharmacology , Alloys , Chromium/chemistry , Corrosion , Electric Impedance , Electrochemistry/methods , Hydrogen-Ion Concentration , In Vitro Techniques , Materials Testing , Microscopy, Electron, Scanning , Oxygen/chemistry , Potentiometry , Spectrum Analysis/methods , Steel , Surface Properties , Temperature , Tensile Strength , Time Factors , Titanium/chemistryABSTRACT
BACKGROUND: Hypertension may be a cause of sepsis, especially among cirrhotic patients. METHODS: In the present investigation we studied the response of the mononuclear phagocytic system in 25 female Holtzman rats divided into five groups of 5 animals each: A, sham-operated animals; and animals with portal hypertension induced by calibrated ligature of the portal vein at different times of evolution: B, 15 days; C, 30 days; D, 45 days; E, 60 days. After the period of observation, 1 MBq/kg 99mTc colloidal sulfur was injected through the caudal vein and the animals were sacrificed 30 minutes later. Blood samples were obtained for GOT, GPT and albumin determination and radioactive counts, and liver, lung, spleen and bone marrow samples were obtained for the determination of the proportional phagocytosis index per gram organ. The results were analyzed statistically by the Kruskal-Wallis test. RESULTS: Increased radioactivity was observed in bone marrow and spleen and higher GPT levels were detected after 15 days. A reduction of splenic phagocytosis, an increase of pulmonary phagocytosis and increased GPT levels occurred after 30 days. In the 45-day group there was an increase in non-phagocytized particles remaining in blood, and in the 60-day group there was only and increase in GPT values. CONCLUSIONS: We conclude that portal hypertension causes phagocytic alterations during the early phases in this experimental model.