Abstract
Electrochemical characterization of stents can be seen as a key to assessing their biocompatibility. The aim of the present study was to investigate the electrochemical properties of bare-metal stent surfaces. The minicell system (MCS) was modified to record open circuit potential (OCP), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) on NiTi, FeCrNi and CoCr stents using 1%NaCl, PBS and serum. Surfaces were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX) before and after electrochemical testing. CV showed passivity breakdown of FeCrNi and CoCr in 1%NaCl. Corrosion properties were inhomogeneous. Several surfaces of FeCrNi showed progressive activation and passivity breakdown while pitting was detected by SEM. EDX showed a decrease in Fe, Cr and Ni and an excessive presence of Cl. Corrosion rates (vcorr) were partially significantly different between the examined materials and electrolytes (e.g. using 1%NaCl: vcorr[FeCrNi]=2.08x10-2±1.14x10-2μm/y vs. [NiTi]=9.41x10 -3 ±1.87x10 -3 μm/y; p<0.001). EIS circuit diagrams indicated oxide films on passivated metal surfaces. The modified MCS is promising to assess the biocompatibility of stents via electrochemical analytics. Overall, the vcorr of all stents were below the required limit values.
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