Dose-Related Effects of Melatonin on Human Osteoblastic Cells via in vitro Controlled Release from Nanoscale Calcium Sulfate

Introduction: Engineering biodegradable scaffolds for bone regeneration in osseous defects is an attractive alternative to harvesting grafts from living tissues. Calcium sulfate based scaffolds can be manufactured to have degradation profiles that are commensurate with new bone growth. However, concerns over the biomechanical strength of calcium sulfate have limited its use to filling small osseous defects. Nanoscale calcium sulfate exhibits enhanced physical properties and can successfully promote bone regeneration in critical-sized craniofacial bone defects. Previous studies show that this bio-ceramic can also accommodate sustainable growth factor delivery to bone cells in vitro. Recently, melatonin has received attention as a potential alternative to recombinant human proteins for use in enhancing the osteoinductive potential of synthetic bone scaffolds. Its clinical efficacy though may be limited by dose-related variation in its stimulatory effects on bone cells. To these ends, the incorporation of melatonin into nanoscale calcium sulfate may give rise to a novel scaffolding system the potential for clinical application in bone regenerative medicine. Materials and Methods: Dose related osteogenic effects of melatonin on human osteoblastic cells were examined by measuring cellular viability and alkaline phosphatase activity. The bioactivity of melatonin released from nanoscale calcium sulfate was assessed through measurement of the viability of cells seeded with the scaffold. Scaffolds containing different amounts of melatonin were then fabricated and the release profiles from each group were characterized. Results and Conclusion: Exposure of human osteoblastic cells to melatonin at micromolar concentrations increased cellular viability and alkaline phosphatase activity. Incorporation of melatonin into nanoscale calcium sulfate increased the viability of cells seeded with the scaffolds. Hence, melatonin released from the scaffolds retained its bioactivity. Release studies showed that nanoscale calcium sulfate can release melatonin in a sustained manner over time. The release profiles though were influenced by the amount of melatonin loaded. This study provided further evidence supportive of the potential use of nanoscale calcium sulfate as a tunable scaffold with the ability to deliver melatonin in quantities stimulatory to bone growth.