Micro-arc oxidation enables tunable mechanical properties, corrosion resistance, and osteoblast compatibility in AZ91D magnesium scaffolds fabricated by 3D printing

Magnesium (Mg) alloys, with their excellent biocompatibility, mechanical properties, and biodegradability, are promising candidates for next-generation bone repair implants. However, the rapid degradation of laser powder bed fusion (L-PBF) fabricated Mg scaffolds severely compromises their mechanical integrity and limits clinical use. Here, we investigate the effect of micro-arc oxidation (MAO) treatment on the compressive behavior, biodegradation, and cytocompatibility of L-PBF AZ91D scaffolds. The MAO coating exhibited a dense, crater-like bio-ceramic morphology that enhanced surface roughness, hydrophilicity, hardness, and corrosion resistance. As a result, the compressive strength increased by 31%, with improved structural integrity and energy absorption. After 7 days of immersion, MAO-treated scaffolds retained over 85% of their original mass, compared to 50% for the untreated samples. Increasing oxidation time produced thicker coatings with stronger substrate adhesion, mitigating coating spallation and further suppressing corrosion. In vitro tests confirmed enhanced cell viability and proliferation due to improved surface bioactivity and moderated Mg²⁺ release. Overall, MAO treatment markedly improves the mechanical performance, corrosion resistance, and cytocompatibility of L-PBF AZ91D scaffolds, offering a viable route toward biodegradable Mg implants with tunable degradation and mechanical compatibility for clinical bone repair applications.