Biological behavior of bone cells on two types of hydroxyapatite incorporated polymer scaffold

Abstract

The gold standard for bone loss treatment is autograft but the problem is insufficient bony source. Therefore we used bone tissue engineering concept to develop biodegradable composite materials for repairing bony defect. First we constructed hydroxyapatite (HAp) incorporated poly (L-lactic acid) (PLLA) by electrospinning technique. We determined morphology and mechanical properties of these scaffold by scanning electron microscope and universal testing machine respectively. For biological testing, we evaluated cytotoxicity and bone biological marker gene expression. From the results we found the increasing of osteocalcin mRNA expression and mineralization in MC3T3-E1, a mouse pre-osteoblastic cell line, culturing on PLLA/HAp scaffolds. The results from mechanical properties and biological responses indicated that the fibrous PLLA/HAp could be the material of choice for use in bone regeneration. The PLLA/HAp scaffolds had satisfiable results and electrospinning technique could construct the fibrous and porous scaffold. However, the drawback of this method is difficulty of producing for different shape and thickness. Therefore we developed Polycaprolactone/HAp (PCL/HAp) scaffold prepared by solvent casting and particulate leaching technique. From this procedure we could create porous size between 400-500 µm. and produeced the appropriated shape and size of the scaffold by proper model. For in vitro analysis, the primary bone cells were cultured with these three dimensional (3D) scaffolds. PCL/HAp promoted proliferation, increased collagen type I and osteocalcin mRNA expression and also mineralization when compared to PCL scaffolds. For in vivo bone regeneration, we implanted the PCL/HAp scaffolds in calvarial mice defect for 6 weeks. The PCL/HAp increased new bone formation when compared to that of PCL. The results from in vitro and in vivo testings showed that the PCL/HAp scaffold could be suitable synthetic material for bone tissue engineering. Further studies in the future, however, may include adding some growth factors and testing with other animal models.