Injectable hydrogels for bone regeneration: mechanical reinforcement strategies using nanoparticles and nanofibers.

Background and Purpose: The growing demand for bone regeneration following severe injuries highlights the importance of scaffolds in bone tissue engineering (BTE). Injectable hydrogels have emerged as promising candidates because their properties closely mimic the native extracellular matrix (ECM). However, their limited mechanical strength and structural instability restrict their practical application. Approach: This review summarizes recent strategies for reinforcing in situ-forming injectable hydrogels to improve their mechanical performance for bone regeneration. Particular emphasis is placed on nanomaterial-based strategies, including the incorporation of nanoparticles and nanofibers, and their ability to enhance the physical properties of polymeric networks. Key Results: Evidence from recent studies demonstrates that reinforcing hydrogels with nano-scaled materials creates interconnected networks that improve load-bearing capacity, stability, and resistance to deformation. These reinforced systems retain the inherent advantages of injectable hydrogels-biocompatibility, biodegradability, permeability to oxygen and nutrients, and drug delivery capability-while addressing their mechanical shortcomings. Conclusion: Nanomaterial-based reinforcement offers a versatile approach to overcoming the limitations of injectable hydrogels in BTE. By providing improved structural integrity alongside biological functionality, these advanced systems broaden the potential of injectable hydrogels for clinical translation. Future work should focus on optimizing reinforcement strategies to balance mechanical enhancement with safety, manufacturability, and regulatory considerations.