Glycoprotein Injectable Hydrogels Promote Accelerated Bone Regeneration through Angiogenesis and Innervation

Recent Advances in Peptide-Functionalized Hydrogels for Bone Tissue Engineering

Efficient therapeutic approaches for bone regeneration are urgently required to address the significant challenges associated with the repair of large-scale or long-segment bone defects. Peptide-functionalized hydrogels (PFHs) have emerged as important bioactive materials in bone tissue engineering because they produce biomimetic microenvironments enriched with multiple biochemical signals. This review summarizes the key fabrication techniques for PFHs and discusses their diverse applications in different fields. Furthermore, we systematically highlighted the biochemical functionalization of PFHs, which includes basic functions such as cell adhesion, cell recruitment, and osteoinduction; improved functions such as angiogenesis, biomineralization, immune regulation, and hormone regulation; and other functions, including antimicrobial and antitumor effects. Finally, critical biosafety considerations associated with PFHs and perspectives on developing intelligent PFHs are addressed. This review aims to inspire further research on PFHs and accelerate their applications in bone tissue engineering.

Strategies for promoting neurovascularization in bone regeneration

Bone tissue relies on the intricate interplay between blood vessels and nerve fibers, both are essential for many physiological and pathological processes of the skeletal system. Blood vessels provide the necessary oxygen and nutrients to nerve and bone tissues, and remove metabolic waste. Concomitantly, nerve fibers precede blood vessels during growth, promote vascularization, and influence bone cells by secreting neurotransmitters to stimulate osteogenesis. Despite the critical roles of both components, current biomaterials generally focus on enhancing intraosseous blood vessel repair, while often neglecting the contribution of nerves. Understanding the distribution and main functions of blood vessels and nerve fibers in bone is crucial for developing effective biomaterials for bone tissue engineering. This review first explores the anatomy of intraosseous blood vessels and nerve fibers, highlighting their vital roles in bone embryonic development, metabolism, and repair. It covers innovative bone regeneration strategies directed at accelerating the intrabony neurovascular system over the past 10 years. The issues covered included material properties (stiffness, surface topography, pore structures, conductivity, and piezoelectricity) and acellular biological factors [neurotrophins, peptides, ribonucleic acids (RNAs), inorganic ions, and exosomes]. Major challenges encountered by neurovascularized materials during their clinical translation have also been highlighted. Furthermore, the review discusses future research directions and potential developments aimed at producing bone repair materials that more accurately mimic the natural healing processes of bone tissue. This review will serve as a valuable reference for researchers and clinicians in developing novel neurovascularized biomaterials and accelerating their translation into clinical practice. By bridging the gap between experimental research and practical application, these advancements have the potential to transform the treatment of bone defects and significantly improve the quality of life for patients with bone-related conditions.

Progress in injectable hydrogels for hard tissue regeneration in the last decade

Bone disorders have increased with increasing the human lifespan, and despite the tissue's ability to self-regeneration, in many congenital problems and hard fractures, bone grafting such as autograft, allograft, and biomaterials implantation through surgery is traditionally used. Because of the adverse effects of these methods, the emergence of injectable hydrogels without the need for surgery and causing more pain for the patient is stunning to develop a new pattern for hard tissue engineering. These materials are formed with various natural and synthetic polymers with a crosslinked network through various chemical methods such as click chemistry, Michael enhancement, Schiff's base and enzymatic reaction and physical interactions with high water absorption which can mimic the environment of cells. The purpose of this research is to review the capabilities of this class of materials in hard tissue regeneration in the last decade through adaptable physical and chemical properties, the ability to fill defect sites with an irregular shape, and the ability to grow hormones or release drugs, in response to external stimuli.

Injectable and In Situ Formed Dual-Network Hydrogel Reinforced by Mesoporous Silica Nanoparticles and Loaded with BMP-4 for the Closure and Repair of Skull Defects

Bone defects are a common and challenging orthopedic problem with poor self-healing ability and long treatment cycles. The difficult-to-heal bone defects cause a significant burden of medical expenses on patients. Currently, biomaterials with mechanical stability, long-lasting action, and osteogenic activity are considered as a suitable way to effectively heal bone defects. Here, an injectable double network (DN) hydrogel prepared using physical and chemical cross-linking methods is designed. The first rigid network is constructed using methylpropenylated hyaluronic acid (HAMA), while the addition of chitosan oligosaccharide (COS) forms a second flexible network by physical cross-linking. The mesoporous silica nanoparticles (MSN) loaded with bone morphogenetic protein-4 (BMP-4) were embedded into DN hydrogel, which not only enhanced the mechanical stability of the hydrogel, but also slowly released BMP-4 to achieve long-term skull repair. The designed composite hydrogel showed an excellent compression property and deformation resistance. In vitro studies confirmed that the HAMA/COS/MSN@BMP-4 hydrogel had good biocompatibility and showed great potential in supporting proliferation and osteogenic differentiation of mouse embryo osteoblast precursor (MC3T3-E1) cells. Furthermore, in vivo studies confirmed that the DN hydrogel successfully filled and closed irregular skull defect wounds, effectively promoted bone regeneration, and significantly promoted bone repair compared with the control group. In addition, HAMA/COS/MSN@BMP-4 hydrogel precursor solution can quickly form hydrogel in situ at the wound by ultraviolet light, which can be applied to the closure and repair of wounds of different shapes, which provides the new way for the treatment of bone defects.