In vitro degradation, biocompatibility and anti-tumor activity of nano-scaled carboplatin-montmorillonite composite coating on magnesium alloy biliary stent in a novel simulated bile solution

Biliary stenting serves as a primary approach to the palliative treatment of malignant biliary tumors, effectively addressing the critical issue of biliary obstruction. However, biodegradable stents are still plagued by the challenge of restenosis caused by rapid tumor growth. Herein, a montmorillonite (MMT) coating was selected to load anti-tumor drug carboplatin (CBP) on biodegradable magnesium (Mg) alloy AZ31 to mitigate its degradation rate, biocompatibility and anti-tumor ability. Based on the Small model, a bile salt-phospholipid-cholesterol-NaCl quaternary solution was designed and carried out as the media of hydrogen evolution, electrochemical and immersion tests to evaluate the corrosion resistance of the biliary stent. The results showed that the CBP-MMT coating possessed a nano-scale microstructure with smooth and compact surface, and a thickness of 18.3 μm and a binding force of 0.25 N between CBP-MMT coating and its Mg substrate. The corrosion rate has decreased from 1.317 mm·year −1 (AZ31 alloy) to 0.149 mm·year −1 (CBP-MMT coating), indicating an improved corrosion resistance. The loading amount of CBP in the CBP-MMT coating is 22.26 mg·g −1 , sustained a release duration for 120 h. In addition, after co-culture with RBE cells (Human Cholangiocarcinoma Cell) in vitro , the CBP-MMT coating displayed an effective anti-tumor ability with a cell activity of 5.75 %. Therefore, the CBP-MMT coating prepared in this study not only improves the corrosion resistance of the stent, but also endows the stent with effective anti-tumor effects, providing a theoretical basis for the applied research on the biliary tract. • CBP-MMT coating was formed on the AZ31 biodegradable biliary stent surface, enabling functionalization of the stent. • A quaternary simulated bile based on the small model was prepared to address inconsistent in-vitro biliary stent conditions. • CBP-MMT coating enables sustained release and synergistic anti-tumor effects with AZ31 degradation products.