The cranial bone in the human body performs very important functions, such as protecting the brain and allowing the passage of cranial nerves that are necessary for normal function. Cranial defects of critical size can disrupt both the physical and psychological well-being of patients. Repair of critical-sized cranial defects with cranioplasty is challenging for reconstructive surgeons, who prefer to use autologous bone grafts. Obtaining autologous bone requires additional surgical procedures that are accompanied by risks such as loss of free flap, infection, deep vein thrombosis, and nerve injury. These limitations require the development of alternatives to autologous bone grafts for the repair of cranial defects.
Biomaterials that mimic the composition and microstructure of natural bone are widely recognized to be ideal for the regeneration of bone defects. The flat bone has two external solid tables of cortical bone. The area between the two tables is called the fold, which consists of cancellous bone. Cortical bone has low porosity (5% to 10%) with interconnected tube-like pores called Haversian canals and Volkmann canals. Cancellous bone is composed of irregular cancellous trabeculae with a high specific surface area, and the mean surface curvature of the trabecular surface is close to zero. The architectural features of cancellous bone are similar to those of a gyroid-type triple periodic minimum surface (TMPS) pore topology.
Inspired by the composition and structural characteristics of cranial bones, scientists from South China University and Technology developed two planar bone-mimetic β-calcium phosphate bioceramic scaffolds (Gyr-Comp and Gyr-Tub) by 3D printing with high photopolymerization accuracy. . Both scaffolds had two outer layers and an inner layer with toroidal pores mimicking the duplex structure. The outer layers of the Gyr-Comp scaffolds simulated the low porosity of the outer tables, while those of the Gyr-Tub scaffolds mimicked the tubular pore structure of the flat bone tables. Gyr-Comp and Gyr-Tub scaffolds possessed higher compressive strength and markedly promoted in vitro cell proliferation, osteogenic differentiation and angiogenic activities compared to conventional scaffolds with cross-link structures. After being implanted in rabbit cranial defects for 12 weeks, the Gyr-Tub achieved the best repair results by accelerating the formation of bone tissue and blood vessels. Gyr-Tub scaffolds have high prospects for the treatment of cranial bone defects in clinical applications. This work provides an advanced strategy to prepare biomimetic biomaterials that match the structural and functional needs of efficient bone regeneration.
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Journal Reference:
Zhang, Y., He, F., Zhang, Q., Lu, H., Yan, S., & Shi, X. (2023). 3D-printed planar bone-mimetic bioceramic scaffolds for cranial reconstruction. Research. doi.org/10.34133/research.0255.
