Development of a novel biomaterial,hydroxyapatite/collagen (HAp/Col) composite for medical use

Abstract

A hydroxyapatite/type I collagen (HAp/Col) composite, aligning hydroxyapatite nano‐crystals along collagen molecules, has been synthesized. The biocompatibility, osteoconductivity and efficacy as an rhBMP‐2 carrier of this novel biomaterial implanted in the weight‐bearing site have been examined. The HAp/Col implants adsorbing 0 or 400 μg/ml of rhBMP‐2 were implanted into bone defects of tibiae in 3 beagle dogs and fixed according to the Ilizarov method. As a control, bone defects of 20 mm remaining in 2 beagle dogs and the dogs were allowed to walk using a Ilizarov external skeletal fixator. The radiological and histological findings suggest that the implants induce bone remodeling units and are a superior carrier of rhBMP‐2 due to the stimulation of early callus and new bone formation. As a next step, anterior fusion was carried out on 6 beagle dogs with the implants adsorbing 400 μg/ml of rhBMP‐2, and 9 dogs with the implants without rhBMP‐2. In 3 dogs of the rhBMP‐treated group, as well as 6 dogs of the non‐rhBMP‐treated group, the implant was fixed with a poly‐L‐lactide plate. Histological and radiographical analysis suggest that enhancement of callus formation and bone bridging by rhBMP‐treatment is effective to prevent collapse of the implant.