Improving the corrosion resistance of AE42 magnesium alloys for cardiovascular stents

Abstract

The present work describes an attempt to increase the life of AE42 magnesium alloy for cardiovascular stents by reducing its degradation rate. Squeeze casted alkali treated AE42 magnesium alloy samples were coated with 2%,4% and 6% powdered carbon fibre reinforced polyetherether ketone (CFRPEEK) in 4% polymethy lmethacrylate (PMMA)using dip coating technique followed by curing at 100°C.Prior to polymer coating the samples were silanized using 3- aminopropyl triethoxysi lane (APTES) and cured at 120°C for 1 hour. The coated samples were characterized by field emission scanning electron microscopy (FESEM),optical microscopy and x-ray diffraction (XRD).The contact angle measurements were done to analyze surface wettability of coated samples. Hemocompatibility and protein adsorption studies were performedto evaluate the percentage hemolysis and amount of protein adsorption on surface of coated and uncoated samples.Hydrogen evolution test was conducted to measure volume of hydrogen evolved on degrading magnesium. Coronary blood flow was simulated with simulated body fluid (SBF)and pH was continuously monitored for 168 hours in flow condition.The FESEM micrographs showed the thickness of the coating to be 43.79 μm on 6% coated sample. Maximum contact angle of 101.55°was observed on 2% coated sample,however,it decreased to 84.3°in 6% coated which may be due to increase in surface roughness. Enhanced hydro phobicity leads to reduction in hemolysis with least hemolysis of 0.2% observed on 6% coated sample.
Large volume of hydrogen evolved on uncoated sample but coated samples`showed a marked decrease with least on 6% coated sample. The rise in pH was also observed to be minimum on 6% coated sample. Further,the a dhesion strength of 5B and hardness of 3H obtained on 6% coated sample proves that the coating is physically robust.The study suggests the suitability of the 6% coated AE42 magnesium alloy for cardiovascular stent applications.