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 syn- thesized HAp and Co2＋-substituted HAp （HAp/Co） designed on the nano-scale with the aim of specifically stimulating osteo- genesis 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 recon- structed 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 pttre HAp. A histological analysis confirmed that the alveolar bone, in which osteoporosis-induced defects were repaired using HAp/Co nanoparticles, was recuperated.

Analysis of the in vitro degradation and the in vivo tissue response to bi-layered 3D-printed scaffolds combining PLA and biphasic PLA/bioglass components--Guidance of the inflammatory response as basis for osteochondral regeneration

The aim of the present study was the in vitro and in vivo analysis of a bi-layered 3D-printed scaffold combining a PLA layer and a biphasic PLA/bioglass G5 layer for regeneration of osteochondral defects in vivo Focus of the in vitro analysis was on the(molecular)weight loss and the morphological and mechanical variations after immersion in SBF.The in vivo study focused on analysis of the tissue reactions and differences in the implant bed vascularization using an established subcutaneous implantation model in CD-1 mice and established histological and histomorphometrical methods.Both scaffold parts kept their structural integrity,while changes in morphology were observed,especially for the PLA/G5 scaffold.Mechanical properties decreased with progressive degradation,while the PLA/G5 scaffolds presented higher compressive modulus than PLA scaffolds.The tissue reaction to PLA included low numbers of BMGCs and minimal vascularization of its implant beds,while the addition of G5 lead to higher numbers of BMGCs and a higher implant bed vascularization.Analysis revealed that the use of a bi-layered scaffold shows the ability to observe distinct in vivo response despite the physical proximity of PLA and PLA/G5 layers.Altogether,the results showed that the addition of G5 enables to reduce scaffold weight loss and to increase mechanical strength.Furthermore,the addition of G5 lead to a higher vascularization of the implant bed required as basis for bone tissue regeneration mediated by higher numbers of BMGCs,while within the PLA parts a significantly lower vascularization was found optimally for chondral regeneration.Thus,this data show that the analyzed bi-layered scaffold may serve as an ideal basis for the regeneration of osteochondral tissue defects.Additionally,the results show that it might be able to reduce the number of experimental animals required as it may be possible to analyze the tissue response to more than one implant in one experimental animal.