Biodegradability, biocompatibility, and mechanical behavior of additively manufactured zinc scaffolds

Zinc is a promising material for biodegradable scaffolds due to its biocompatible nature and suitable degradation rate. However, its low mechanical strength limits its use in load-bearing applications. This study aims to address this challenge by optimizing the process parameters of pure zinc using laser-based powder bed fusion and designing zinc scaffolds with tailored structures. Scaffolds based on five different unit cell types (Diamond, gyroid, primitive, Fischer-Kock S, and I-WP) were designed and fabricated using the optimized process parameters. The resulting scaffolds were evaluated for mechanical properties, degradation behavior, and cytocompatibility evaluation. Results show that I-WP and primitive scaffolds exhibited superior mechanical properties with compressive yield strength of 36.1 ± 1.2 MPa and 33.5 ± 1.4 MPa, respectively. While all scaffolds displayed a degradation rate within the range of 0.14-0.15 mm/year, the I-WP and primitive design exhibited a slightly higher degradation rate (0.15 mm/year) compared to the gyroid, diamond, and Fischer Koch S scaffolds (0.14 mm/year). Zinc itself demonstrated excellent cytocompatibility, as evidenced by in vitro MTT assay and cell morphology studies. Unit cell morphology also could accelerate proliferation, where MG-63 cells formed bridges between the unit cell walls in Fischer Koch S scaffolds. Considering the targeted application (mandible or jawbone healing) and evaluating all findings, scaffolds with I-WP and primitive designs and wall thicknesses of 500 μm (S01) emerged as the most promising candidates in mandible healing injuries.