Enhanced Osteogenesis of Nanosized Cobalt-substituted Hydroxyapatite

Hydroxyapatite (HAp) is an extensively studied material with known biocompatible and osteoconductive properties in bone tissue reconstruction. The improvement of the osteogenetic potential of HAp has been tested through modification of its structure, by replacing Ca2+ ions with Co2+ ions. In our study, we comparatively analyze the osteogenetic potential of the synthesized HAp and Co2+-substituted HAp (HAp/Co) designed on the nano-scale with the aim of specifically stimulating osteogenesis in vivo. We present a quantitative study of the microscopic organization and structure of the newly formed tissue in a bone defect after 12 weeks and 24 weeks. A quantitative analysis of the calcium, magnesium and phosphorus content in the defect and its close environment was used to determine the deposition of minerals after bone reconstruction. The defect reconstructed with HAp/Co nanoparticles (Co2+ content 12 wt%) was filled with a new tissue matrix composed of dense collagen fibers containing centers of mineralization after 24 weeks. The mineral deposition rate was also higher when the defect was reconstructed with HAp/Co than when it was filled with pure HAp. A histological analysis confirmed that the alveolar bone, in which osteoporosis-induced defects were repaired using HAp/Co nanoparticles, was recuperated.