Corrosion-microenvironment-responsive etidronate-loaded alkali lignin nanoparticle/silane coating for degradation regulation of ZE21C magnesium alloy

Rapid degradation and local alkalization limit the orthopedic use of biodegradable magnesium alloys. An MS-ETN@ALNPs coating was constructed on ZE21C alloy through micro-arc oxidation, APTMS sealing, and incorporation of etidronate disodium-loaded alkali lignin nanoparticles. Microscopy and spectroscopy verified a continuous multilayer structure and the presence of ETN-related phosphorus groups. Isolated ETN@ALNPs released more ETN under alkaline conditions. The composite coating retained an adhesion-related critical load of approximately 75 mN and achieved a corrosion current density of (2.20 ± 1.57) × 10 −7 A·cm −2 and a charge-transfer resistance of 2406.0 ± 46.39 Ω·cm 2 . After 7 days in simulated body fluid, it produced the lowest weight loss, least surface damage, and reduced hydrogen evolution. Extracts from the coated samples also promoted MC3T3-E1 cell adhesion and spreading. The coating therefore provided effective degradation control while preserving a cellular environment favorable to osteoblast attachment.