Development of Skeletal Drug Delivery System Based on Apatite/Collagen Composite Cement

Abstract

Since bone resorption and formation occur repeatedly within the functional units referred to as bone multicellular units, uncoupling between bone resorption by osteoclasts and bone formation by osteoblasts causes an absolute decrease in the amount of bone in osteoporosis. For that reason, it is necessary to fully understand the remodeling characteristics of bone grafts by osteoclasts and osteoblasts to high-bioactivematerials.We have, therefore, prepared hydroxyapatite (HAp) and collagen composites to improve bioaffinity through the interaction between materials and bone cells for applications in drug delivery devices. Apatite/collagen composite cements could be applied to artificial bone drug delivery systems without drug inactivation caused by high pressure and those that exhibit long-term slow drug release in vitro and high in vivo biocompatibility in osteoporosis model rats. On the other hand, geometrical structure of pores in implantable artificial bone has been proven successful in bone generation, since bone-related cells can be cultured more readily in interconnected porous materials, such as coral-modified implant made by calcium phosphate. Interconnective pores in coral-like material are therapeutically effective in bone regeneration within the body through the introduction of bone cells and capitally blood vessels as a scaffold for bone cells to spread and proliferate. The interconnective porous biomaterials are, therefore, developed based on self-setting apatite/collagen composite cement as materials with enhanced biocompatibility and drug delivery capability. Since the drug release rate from the composite device could be controlled by various geometrical factors, the relationship between drug-release rate and number of the macropores was investigated by in vitro dissolution test. Bioaffinity of the interconnective porous biomaterials of apatite/collagen composite cement was examined in rat models using X-ray computed tomography.