Achieving bone regeneration and adhesion with harmless visible light

Bone defects, which arise from various causes such as trauma, infection, and congenital abnormalities, are becoming increasingly common in aging societies. Conventional treatments often involve bone grafts combined with serum or bioadhesives to fill the defect. However, existing injectable hydrogels face challenges such as difficulty in maintaining their shape within the body and limited adhesive strength. Moreover, traditional methods using bone grafts with adhesive materials often fail to achieve simultaneous "bone regeneration" and "adhesion."

The POSTECH team has introduced a novel system that addresses these limitations. This new hydrogel system employs visible light -- safe for the human body -- to facilitate cross-linking, where the main components of the hydrogel bond and harden, and to simultaneously boost mineralization where bone-building minerals like calcium and phosphate form within the hydrogel. While earlier studies have explored the use of light in similar applications, they encountered issues such as requiring separate preparation and mixing of bone grafts and adhesive materials, as well as weak bonding of the main components, which often degraded over time.

The newly developed hydrogel precursor comprises alginate (natural polysaccharide derived from brown algae), RGD peptide-containing mussel adhesive protein, calcium ions, phosphonodiols, and a photoinitiator. The coacervate-based formulation, which is immiscible in water, ensures that the hydrogel retains its shape and position after injection into the body. Upon visible light irradiation, cross-linking occurs, and amorphous calcium phosphate, which functions as a bone graft material, is simultaneously formed. This eliminates the need for separate bone grafts or adhesives, enabling the hydrogel to provide both bone regeneration and adhesion.

In experiments using animal models with femoral bone defects, the hydrogel was successfully injected, adhered accurately, and effectively delivered components essential for bone regeneration.

Professor Cha commented, "The injectable hydrogel system for bone regeneration developed by our research team represents an innovative alternative to conventional complex treatments for bone diseases and will greatly advance bone tissue regeneration technology."

This research was supported by the Ministry of Health and Welfare's Dental Medical Technology Research and Development Project and the Integrated End-to-End Medical Device R&D Project.