Inorganic-organic composite protective coating for biodegradable metal ureteral stents

Abstract

Conventional ureteral stents are made of non-biodegradable polymers or metals and often need secondary surgical removal. Biodegradable ureteral stents offer advantages in reducing urethral inflammation and scaling, avoiding secondary surgical removal of the stent, and improving patient comfort. In this study, a novel inorganic-organic composite protective coating consisting of an inorganic inner layer of magnesium hydroxide-magnesium fluoride (Mg(OH)₂–MgF₂) and an organic outer layer of poly(trimethylene) carbonate (PTMC) was prepared on biodegradable magnesium ureteral stents using a simple and low-cost method. Electrochemical tests showed that the composite coating significantly improved the corrosion resistance of magnesium, reducing the I_corr value from 45.53 μA·cm⁻² to 3.58 μA·cm⁻², and significantly reducing the P_i value. In addition, the in vitro immersion tests showed that the weight loss of the composite coated samples was only 2.58 mg over 7 days, which was significantly lower than that of bare magnesium, which was 5.62 mg. Additionally, the pH change was minimal (from 6.53 to 6.77 ± 0.01), and Mg²⁺ release was effectively controlled at 35.98 mg·L⁻¹. The coating significantly improves the corrosion resistance of magnesium stents, reduces localized corrosion and Mg²⁺ release, while exhibiting good blood compatibility (<5 %). Biodegradable composite protective coatings are expected to reduce complications associated with conventional stents and improve patient outcomes, showing excellent potential for ureteral stent applications.