Biomaterials for Craniofacial Bone Regeneration

Bone tissue needs complex systems to return to its standard shape and function. During bone mending, cells that release cytokines, growth factors, and substances that cause inflammation in the area of the hole will draw nearby stem cells to move, multiply, and change into bone-forming cells. When the body cannot fully recover the destroyed tissue, bioactive functional scaffolds may be used to help the bone mend. Bone defect in dental becomes a prevalent maxillofacial disease, resulting in mandibular dysfunctions and huge psychological burdens to the patients. Considering the routine presence of oral contaminations and aesthetic restoration of facial structures, the current clinical treatments are limited and incapable of reconstructing the structural integrity and regeneration, spurring the need for cost-effective dental bone tissue engineering. Hydrogel systems possess great merit for dental bone tissue reconstruction with precise involvement of cells and bioactive factors. This study reviews hydrogel-related dental bone tissue engineering. It provides an update on the advanced fabrication of hydrogels with improved mechanical properties, antibacterial ability, injectable form, and 3D bioprinted hydrogel constructs. Exploring advanced hydrogel systems will lay a solid foundation for a bright future with more biocompatible, effective, and personalized treatment in mandibular reconstruction.

Tracheal stenosis has been a challenging issue for medical practitioners; however, tissue engineering technology has promoted the development of tissue-engineered trachea (TET) for tracheal replacement therapy. Seed cells, scaffold materials, and bioactive factors are required to construct a TET. The optimal combination of these components is necessary to construct TETs with good mechanical strength, histocompatibility, and functionalization that promote tracheal transplantation and reconstruction of airway function. This review critically evaluates the advancements in tracheal tissue engineering concerning the progression and practical utilization of biomaterials in TET construction. First, we outline the history of tracheal tissue engineering development. Second, we comprehensively review the materials used to prepare TETs, focusing on newly emerging biomaterials. Finally, we present our views on the applications of novel materials and prospective avenues for further investigation in tracheal tissue engineering. This review promotes the inter-disciplinary exchange of ideas across clinical medicine, tissue engineering technology, and biomaterials.

The repair of large-size cranial bone defects caused by traumatic brain injury (TBI) remains a substantial clinical challenge. On one hand, traditional bone implants with intrinsic brittle and poor recovery features hinder their immediate implantation for cranioplasty applications. On the other hand, using exogenous growth factors to enhance the osteo-bioactivity of bone implants often leads to efficacy, safety, and cost concerns. Thus far, the authors develop a growth factor-free pliable hydrogel with multiple functions for mediating endogenous growth factor production and stem cell functions in cranioplasty. The pliable hydrogels are based on GelMA networks, in which the mechanical properties and protein affinity were strengthened by the crosslinked poly (ethylene glycol) disuccinimidyl succinate (PEG-(SS)₂), while the antioxidant capability and osteoinductivity were remarkedly enhanced through the decoration of magnesium-seamed C-propylpyrogallol[4]arene cages (PgC₃Mg). In vitro and in vivo results confirmed that the versatile hydrogel with excellent biocompatibility and biodegradability can improve osteogenic differentiation and cranial bone regeneration by facilitating growth factor production, endogenous cell recruitment and angiogenesis. These findings indicate that the versatile hydrogels represent a potential avenue for developing growth factor-free pliable scaffolds in cranioplasty after TBI.

Vascularization plays a crucial role in transporting and exchanging nutrients and oxygen between implanted grafts with the host tissue. In the biofabrication of the implanted grafts, remodeling the vascular networks can accelerate vascularized tissue repair and regeneration. Given the heterogeneity of vascular networks in vascularized tissues, traditional scaffold manufacturing techniques cannot effectively achieve vascular with various scales in vitro and in vivo biomimetic. In recent years, 3D bioprinting technologies have been widely used in fabricating various 3D grafts for tissue repair and regeneration due to their shape customizability, simple manufacturing procedure, reproducibility, and precise multi-dimensional control. With the rapid development of 3D bioprinting technologies, bioprinting-based biofabrication strategies have been gradually applied in the construction of various vascularized tissues. Based on this background, our study aimed to review recent advances, challenges, and future perspectives in biofabrication strategies based on bioprinting for vascularized tissue repair and regeneration. The bioprinting techniques, bioinks, seed cells, and growth factors used for vascularized tissue construction were also enrolled in this review. In addition, the bioprinting history, vessel formation mechanism, and histology of vascular networks in vascularized tissue were also discussed.