Light-cured hyaluronic acid composite hydrogels using riboflavin as a photoinitiator for bone regeneration applications

Objective: Self-healing of bone from damage caused by infection, trauma, or surgical removal of cysts is limited. Generally, external intervention is needed to increase bone repair and regeneration. In this study, biocompatible light-cured hyaluronic acid hydrogels loaded with nano-hydroxyapatite and chitosan were prepared using a new photoinitiating system based on riboflavin for bone regeneration applications. Method: Four light-cured hydrogel groups were prepared as follows: Group I, a control group with no additions; Group II, loaded with nano-hydroxyapatite; Group HI, loaded with chitosan; and Group IV, loaded with both nano-hydroxyapatite and chitosan. The new photoinitiating system consisted of riboflavin as a pho toinitiator, dimethylaminoethyl methacrylate (DMAEMA) as a coinitiator (being used with riboflavin for the first time), and diphenyliodonium chloride as an accelerator. For each group, X-ray-diffraction, surface morphology by scanning electron microscope, mechanical properties, water uptake (%), and cell viability (%) were tested. The osteogenic potential was then tested in a rabbit model, and histomorphometric assessment was conducted. Results: In the four groups, the light-cured hydrogels were obtained after a short irradiation time of 10 s using a dental light-curing unit. The prepared hydrogels were biocompatible. Simultaneous addition of nano-hydroxyapatite and chitosan increased the mechanical properties threefold and the osteogenic potential, twofold, with a statistically significant difference compared with the control group. Conclusions: Light-cured hyaluronic acid composite hydrogels loaded with nano-hydroxyapatite and chitosan-prepared by using the new photoinitiating system-are promising materials that can be used in bone regeneration applications.