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Decellularization is a promising new method to prepare natural matrices for tissue regeneration. Successful decellularization has been reported using various tissues including skin, tendon, and cartilage, though studies using hard tissue such as bone are lacking. In this study, we aimed to define the optimal experimental parameters to decellularize natural bone matrix using 0.5% sodium dodecyl sulfate and 0.1% NH4OH. Then, the effects of decellularized bone matrix on rat mesenchymal stem cell proliferation, osteogenic gene expression, and osteogenic differentiations in a two-dimensional culture system were investigated. Decellularized bone was also evaluated with regard to cytotoxicity, biochemical, and mechanical characteristics in vitro. Evidence of complete decellularization was shown through hematoxylin and eosin staining and DNA measurements. Decellularized bone matrix displayed a cytocompatible property, conserved structure, mechanical strength, and mineral content comparable to natural bone. To study new bone formation, implantation of decellularized bone matrix particles seeded with rat mesenchymal stem cells was conducted using an orthotopic in vivo model. After 3 months post-implantation into a critical-sized defect in rat calvaria, new bone was formed around decellularized bone matrix particles and also merged with new bone between decellularized bone matrix particles. New bone formation was analyzed with micro computed tomography, mineral apposition rate, and histomorphometry. Decellularized bone matrix stimulated mesenchymal stem cell proliferation and osteogenic differentiation in vitro and in vivo, achieving effective bone regeneration and thereby serving as a promising biological bone graft.

A hydroxyapatite-collagen (HC) composite material can mimic composition and ultra-structures of natural bone and provide adequate bioactive material-tissue interactions. Incorporation of dopamine (DA) is one of keys in increasing the mechanical strength of the HC material to approaching that of cortical bone. In this study, the in vitro osteogenic effects of polydopamine-laced hydroxyapatite collagen calcium silicate (HCCS-PDA) were examined by culturing rat mesenchymal stem cells (rMSCs) on HCCS-PDA and HCCS coated plates. HCCS-PDA group demonstrated less cytotoxic from Live/Dead cytotoxic assay and displayed higher cell attachment, proliferation and mineralization than the HCCS group in vitro. For in vivo bone regeneration, HCCS-PDA or HCCS particulates with or without rMSC aggregates were implanted into rat critical-sized calvarial defects (CSD). After 12 weeks, calvarial bone regeneration was evaluated radiographically, histologically, and histomorphometrically. While the majority of new bone formation occurred around the HCCS-PDA particulates with rMSC aggregates, The HCCS-PDA particulates without rMSC aggregates showed limited osteoconductivity. HCCS with or without rMSC aggregates resulted in less bone formation, indicating a prominent role of DA in effective bone regeneration. Therefore, the HCCS-PDA biomaterial with the aid of rMSCs can be used to develop therapeutic strategies in bone tissue engineering with numerable clinical applications.

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Purpose The strength of printed parts by application of fused deposition modeling (FDM) has been broadly studied through experimental methods. However, constitutive behaviors of the printed parts in theory are still unclear. Therefore, this paper aims to focus on building an elasto-plastic model of the printed parts to reveal the constitutive behavior. Design/methodology/approach An elasto-plastic constitutive model that considers anisotropic characteristics is proposed. Tensile tests are performed for parameter identification by using different samples with varying printing angles. Finally, the constitutive model is completed and applied to the numerical analysis of a tensile procedure. Findings The experimental study indicated that the anisotropic characteristics are significant for elastic modulus and strength of printed parts. The polar anisotropic model is suitable for describing the anisotropic behavior of parts during the elastic deformation. The Hill model is suitable to describe the yield property. The elastic modulus and yield point of parts printed in any specific orientation can be calculated using the proposed constitutive model. Originality/value A theoretical model has been developed to describe the constitutive behavior of FDM printed part. This model can precisely describe the elastic behavior and yield point of parts printed with various orientations. This model can be applied to the finite element simulation of printed structures.