Tissue Engineering Strategies for Alveolar Bone Regeneration Using Silk-Based 3D-Printed Composite Scaffolds

Abstract

Successful regeneration of the alveolar ridge requires biomaterials that support both osteogenesis and vascularization. Combining biomaterials with 3D printing technology supports the fabrication of customized scaffolds with controlled architecture tailored to bone repair. This thesis explores two distinct tissue engineering strategies for bone regeneration using silk fibroin (SF)-based 3D printed scaffolds. The first approach involves SF-biphasic calcium phosphate (SF-BCP) scaffolds functionalized with bone morphogenetic protein-2 (BMP-2) and platelet-derived growth factor (PDGF), delivered using a heparinized hyaluronic acid-based hydrogel injected inside the scaffolds. The second strategy employed a cell co-culture-based regeneration approach using SF-bioactive glass (SF-BG) scaffolds designed to support the direct culture of human mesenchymal stem cells (hMSCs) with human umbilical vein endothelial cells (HUVECs) for vascularized bone tissue regeneration. The SF-BCP scaffolds were fabricated using an extrusionbased 3D printing method and characterized for their mechanical, structural, and rheological properties. Functionalization of the scaffolds with BMP-2 significantly enhanced early osteogenic differentiation, while PDGF had a limited effect. In parallel, SF-BG scaffolds were developed to support direct co-culture. The rheological and mechanical properties were suitable for the goals, but the printing process was sensitive to small changes in formulation and thus, less reliable. Coculture conditions were optimized on tissue culture polystyrene (TCPS) and then translated to the 3D printed scaffolds. The cells successfully adhered to the constructs, proliferated, and maintained increasing levels of metabolic activity over time. The scaffolds supported extracellular matrix deposition, with features varying depending on the ratios of hMSCs and HUVECs in the co-cultures. Altogether, this work demonstrates the potential of SF-based 3D printed scaffolds to support bone regeneration through bioengineering strategies tailored to enhance osteogenic outcomes. The findings of this work offer a foundation for the future design of silk-based scaffolds with potential applications in the regeneration of alveolar and craniofacial bone tissues.