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Electrospun three dimensional scaffolds for bone tissue regeneration

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Bone is a complex and highly specialized form of connective tissue which acts as the main supporting organ of the body. It is hard and dynamic by its nature, with a unique combination of organic and inorganic elements embedded in a fibrous extracellular matrix (ECM), onto which cells attach, proliferate and differentiate. When bone repair mechanisms fail, due to infection or defect magnitude, bone formation can be stimulated with the use of autologous bone grafts or donor allografts. However, autografts are associated with limitations such as donor site morbidity and limited availability, while allografts have the potential to cause an immune response and also carry the risk of pathogen transfer. Bone tissue engineering has emerged as an alternative to these approaches by attempting to mimic the architecture of the bone tissue while providing appropriate cues for cellular attachment, growth and proliferation, as well as the mechanical strength necessary to maintain their structural integrity during remodelling. The present study aims to create three dimensional fibrous scaffolds containing nano-hydroxyapatite (nHAp) embedded in a matrix of functional biomacromolecules, polyhydroxybutyrate/hydroxyvalerate (PHB/PHV) and Bombyx mori silk fibroin (SF) with the use of the simple and versatile technique of electrospinning. This approach will offer an attractive route to mimicking the natural bone tissue architecture through electrospinng of the ceramic phase within the polymeric one. The created functional fibrous substrates could be used for in vitro or in vivo tissue regeneration. For these reasons they are intended to support cell attachment, proliferation and differentiation, while the role of nHAp would be to induce cells to secrete ECM for mineralization to form bone. After choosing the materials, screening tests were conducted to determine a suitable composite solution and its electrospinning parameters, followed by a Design of Experiments analysis in order to explore and understand the relationship between process factors: feed rate, voltage, collection distance and solution composition. Physico-chemical and in vitro biological tests were performed on produced constructs in order to study the suitability of the proposed material combination for such an application. Simultaneous electrospinning of composites of 2% valerate fraction PHB/PHV , nano hydroxyapatite (nHAp), and Bombyx mori silk fibroin (SF) has been achieved for nHAp and SF solution concentrations of 2 (w/vol) % each and 5 (w/vol) % each and three dimensional fibrous scaffolds were constructed. Further findings of this work supported the hypothesis that the proposed composite scaffolds have appropiate fibrous morphology of the ECM showing continuous fibres deposition and no bead defect formation. Furthermore the structures support apatite formation on their surface, thus being bioactive while exhibiting a low degradation rate that is adequate for bone regeneration. The 2% composite constructs (2% nHAp and 2% SF content) possess appropriate compressive properties for bone tissue regeneration while the Young’s modulus varies with the ceramic/ proteic content. Additionally when placed in culture the 3D structures enhance the osteoblast phenotype with cells travelling in the depth of the construct after only 3 days after seeding. All these resultssuggest that these scaffolds are appropriate cell carriers for osseous tissue engineering, offering an alternative in the biomaterials area of study.

 

http://doras.dcu.ie/19371/