Degradation-Mediated Bioactive Calcium Release from Alginate Gel Fibers for Enhanced Bone Regeneration

Biodegradable hydrogels are promising for bone regeneration but are limited by a significant mechanical mismatch with bone tissue in modulus, strength, and toughness. To address the weakness, this work reported a mesh-like hydrogel woven from calcium-alginate gel fibers. The fibers, manufactured via wet-spinning, possessed tensile strengths (36-285 MPa) and moduli (200 MPa-9.1 GPa) comparable to those of bone tissue. This feature made the woven hydrogel withstand complex physiological loads while maintaining its biodegradable properties. In vitro, the degraded hydrogel promoted the osteogenic differentiation of rat bone mesenchymal stem cells, achieving 155% increment of alkaline phosphatase (ALP) activity and 294% increment of mineralized calcium nodules. After implantation into cranial bone defects in vivo, complete biodegradation resulted in continuous release of bioactive calcium, significantly accelerating bone regeneration and achieving a regenerated bone volume to tissue volume (BV/TV) ratio of 67.2%. This study demonstrates a paradigm of degradation-mediated nutrient release, highlighting the pivotal role of bioactive calcium delivery for effective bone regeneration.