In vitro biological properties of chitosan and polydopamine-based biopolymer surfaces fabricated on AZ61L alloys

In this study, chitosan, polydopamine and polydopamine/chitosan coatings were coated on AZ61L magnesium by dip coating process. Thus, the surface characteristics, wettability and in vitro biological properties including bacteria and cell behavior of chitosan (Mg-C), polydopamine (Mg-D), polydopamine/chitosan (Mg-C-D) layers fabricated on AZ61L alloy were investigated in this work. The surfaces were characterized by X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, contact angle goniometer and surface profilometer. The Mg-D and Mg-C coatings indicated hydrophilic behavior while the Mg-C-D coatings exhibited hydrophobic character. Cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, while cell death was confirmed by acridine orange/propidium iodide fluorescence staining. The results demonstrated that all coated surfaces significantly improved cellular responses compared to bare Mg, with the Mg-C-D coating exhibiting the highest cell viability and enhanced cytocompatibility. Antibacterial activity was determined using the agar diffusion method against Staphylococcus aureus (ATCC6538). Furthermore, antibacterial tests revealed that Mg-C-D surfaces showed superior inhibition against bacterial growth compared to single-layer coatings, indicating a synergistic effect between chitosan and polydopamine. These findings demonstrate that the combined coating strategy provides an effective approach to enhance both biocompatibility and antibacterial performance of Mg-based alloys for biomedical applications.