Additively Manufactured Zn‐2Mg Alloy Porous Scaffolds with Customizable Biodegradable Performance and Enhanced Osteogenic Ability

Abstract

The combination of bioactive Zn‐2Mg alloy and additively manufactured porous scaffold is expected to achieve customizable biodegradable performance and enhanced bone regeneration. Herein, Zn‐2Mg alloy scaffolds with different porosities, including 40% (G‐40‐2), 60% (G‐60‐2), and 80% (G‐80‐2), and different unit sizes, including 1.5 mm (G‐60‐1.5), 2 mm (G‐60‐2), and 2.5 mm (G‐60‐2.5), are manufactured by a triply periodic minimal surface design and a reliable laser powder bed fusion process. With the same unit size, compressive strength (CS) and elastic modulus (EM) of scaffolds substantially decrease with increasing porosities. With the same porosity, CS and EM just slightly decrease with increasing unit sizes. The weight loss after degradation increases with increasing porosities and decreasing unit sizes. In vivo tests indicate that Zn‐2Mg alloy scaffolds exhibit satisfactory biocompatibility and osteogenic ability. The osteogenic ability of scaffolds is mainly determined by their physical and chemical characteristics. Scaffolds with lower porosities and smaller unit sizes show better osteogenesis due to their suitable pore size and larger surface area. The results indicate that the biodegradable performance of scaffolds can be accurately regulated on a large scale by structure design and the additively manufactured Zn‐2Mg alloy scaffolds have improved osteogenic ability for treating bone defects.

Multiscale architecture design of 3D printed biodegradable Zn-based porous scaffolds for immunomodulatory osteogenesis

“…Usually, unmelted powders and defects will cover the surface of porous scaffolds and play negative role on their biological performance. Few studies have looked into the surface quality of 3Dprinted biodegradable metals as coarse surface morphology with large amounts of unmelted powders are commonly seen in 3D-printed Znbased bone scaffolds, which prevent the new bone tissue from ingrowth and osseointegration 10,12 . From our perspective, surface treatment can be an important way to regulate the early inflammatory immune response of bone injury.…”

“…For example, multicellular spatiotemporal organization of pre-osteoblasts indicates cells prefer regions with at least one negative principal curvature 23 . The degradation of Zn alloy scaffolds increases positively with porosity while negatively with pore size 10 . Therefore, multiscale architecture design for biodegradable Zn-based porous scaffolds may successfully orchestrate the immune cell responses and the subsequent bone regeneration.…”

“…These in vivo and clinical studies reveal a discouraging mismatch that the degradation of bulk Zn-based implants may typically require a decade or more, while the physiological cycle of bone repair spans only 3-6 months. In the past three years, the 3D printing technology based on novel biodegradable Zn alloys has rapidly advanced, aiming to reduce material consumption while maintaining sufficient mechanical performance through innovative structural designs [10][11][12] . However, overdose-induced Zn toxicity caused by accelerated degradation is a critical challenge in Zn-based porous scaffolds due to the increased porosity and specific surface area in comparison to bulk materials 13 .…”

An adaptive biodegradable zinc alloy with bidirectional regulation of bone homeostasis for treating fractures and aged bone defects

“…Both binary and ternary Zn alloys comprising different alloying elements show stable osteogenic promotion effects [ 40 , 41 ]. The stimulation of bone formation by Zn–Mg alloys has been extensively studied; however, the mechanism of osteogenic differentiation induced by Zn–Mg alloys remains unclear [ 42 , 43 ]. Similar to Zn–Li and Zn–Sr alloys, we found that Zn-0.8 Mg alloys also promote osteogenesis by activating the Pi3k-Akt signaling pathway [ 16 , 44 ].…”

“…Here, the compressive strength of the Zn-0.8 Mg alloy scaffold with 80 % porosity was 7.43 ± 0.62 MPa, which was within the compressive strength range of cancellous bone (2–12 MPa), meaning that the proposed alloy can provide adequate mechanical support for bone defects of the femoral condyle. In our previous study, 80%-porosity Zn–2Mg scaffold exhibited better biocompatibility and osteogenesis promotion [ 43 ]. Therefore, to evaluate the therapeutic effect of Zn-0.8 Mg scaffolds on bone defects with low bone metabolism status, 80%-porosity of scaffolds were selected.…”