The critical role of surface characteristics in 3D-printed biodegradable Zn-based porous scaffolds for bone defect repair

Surface properties of implants significantly influence bone regeneration. However, the understanding of surface characteristics in 3D-printed biodegradable Zn-based porous scaffolds is limited, and their impact on osteogenesis remains unclear. Here, Zn and Zn-1Mg porous scaffolds were additively manufactured using laser powder bed fusion, and acid etching was applied to polish the surface. The surface roughness, composition, and wettability were investigated. In vitro and in vivo tests were conducted to evaluate their impact on osteogenesis. Oxidation layers with thicknesses of 10–40 nm, were observed on the powder-fused surfaces of as-built scaffolds. Acid etching reduced surface roughness, water contact angle, and oxidation layer thickness. The concentration of Zn²⁺ released from acid-etched Zn scaffolds was approximately twice that of the as-built scaffolds, attributed to a thinned oxidation layer and improved wettability. Acid-etched Zn scaffolds exhibited inferior bone regeneration due to elevated Zn²⁺ release, triggering pro-inflammatory responses and impairing osteogenic potential. Alloying with Mg enhanced osteogenesis by decreasing Zn²⁺ release and introducing osteogenesis-favourable Mg²⁺, primarily resulting from the presence of Mg-containing phases on the surface. This study offers key insights into how surface characteristics influence osteogenesis in biodegradable scaffolds, guiding the design of more effective orthopedic implants.