Abstract
The biodegradable ability of magnesium alloys is an attractive feature for tracheal stents since they can be absorbed by the body through gradual degradation after healing of the airway structure, which can reduce the risk of inflammation caused by long-term implantation and prevent the repetitive surgery for removal of existing stent. In this study, the effects of bicarbonate ion (HCO3−) and mucin in Gamble’s solution on the corrosion behavior of AZ31 magnesium alloy were investigated, using immersion and electrochemical tests to systematically identify the biodegradation kinetics of magnesium alloy under in vitro environment, mimicking the epithelial mucus surfaces in a trachea for development of biodegradable airway stents. Analysis of corrosion products after immersion test was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) was used to identify the effects of bicarbonate ions and mucin on the corrosion behavior of AZ31 magnesium alloys with the temporal change of corrosion resistance. The results show that the increase of the bicarbonate ions in Gamble’s solution accelerates the dissolution of AZ31 magnesium alloy, while the addition of mucin retards the corrosion. The experimental data in this work is intended to be used as foundational knowledge to predict the corrosion behavior of AZ31 magnesium alloy in the airway environment while providing degradation information for future in vivo studies.
Highlights
Patients with airway collapse often have cough, inability to clear secretions, and even respiratory failure requiring mechanical ventilation [1,2] and can lead to dyspnea, hemorrhage and obstructive pneumonia [3]
This paper presents the corrosion behaviors of AZ31 magnesium alloy with the concentrations of bicarbonate ion (HCO3−) and mucin in Gamble solution that mimics the airway surface lining fluid
The surface of AZ31 magnesium alloy after immersion in solution #1 without NaHCO3 and mucin was covered with white corrosion products
Summary
Patients with airway collapse often have cough, inability to clear secretions, and even respiratory failure requiring mechanical ventilation [1,2] and can lead to dyspnea, hemorrhage and obstructive pneumonia [3]. Airway stents are placed in the airway of patients to restore airway patency caused by stenosis [4,5] This is accomplished by using permanent stents made from various metals such as stainless steel, cobalt-based super alloy, nitinol (Ni-Ti alloy) or silicone [5,6], the use of these permanent materials can increase the risk of local inflammation occurring after long-term implantation, which may require open surgery because the stent covered by epithelium are difficult to be removed by conventional bronchoscopic procedure [6,7]. It is necessary to systematically identify the corrosion behaviors of magnesium alloys in simulated respiratory fluids for successful development of biodegradable airway stents. The fundamental knowledge gained from in vitro corrosion studies will provide a basis to help understand the corrosion mechanisms of magnesium alloys under in vivo airway environment
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