Functional Surface Modification of Magnesium Implant by Drug-Loaded Biodegradable Polymer Coating

Magnesium has attracted attention as an orthopedic implant material due to its excellent biocompatibility and biodegradability; however, rapid corrosion in physiological environments remains a major limitation. In this study, a polydopamine (PDA) intermediate layer and alginate/chitosan multilayer coating were formed on pure magnesium surfaces, with dexamethasone incorporation to simultaneously improve corrosion resistance and bioactivity. SEM observation revealed that uniform coating layers were formed on alginate/chitosan multilayer coated specimens, and the chemical structure of the coating layers was confirmed through FT-IR and XRD analyses. Electrochemical analysis revealed that the PDA/alginate/chitosan coating group exhibited higher corrosion potential (Ecorr: −0.7514 ± 0.022 V vs. −1.706 ± 0.001 V) and lower corrosion current density (icorr: 2.275 ± 0.15 × 10⁻⁷ A/cm² vs. 1.528 ± 0.47 × 10⁻⁴ A/cm²) compared to pure magnesium, with the highest impedance indicating superior corrosion resistance. In tape peel testing, the polydopamine-coated group demonstrated superior adhesion compared to the non-coated group, and sustained release of dexamethasone was confirmed. MC3T3-E1 cell culture results confirmed cell proliferation in all specimens, with the PDA/alginate/chitosan group exhibiting the highest ALP activity compared to other surface-treated groups. Based on these results, the PDA/alginate/chitosan multilayer coating was confirmed to be an effective surface modification method for corrosion control and promotion of osteoblast differentiation on magnesium.