Abstract
Tissue engineering for skeletal applications has seen outstanding progress due to the advent of additive manufacturing (AM) and the development of novel biomaterials, leading to the birth of biofabrication and the promise of in vitro engineering of functional ‘living’ constructs. However, there is a discrepancy between materials with optimal processing properties for AM and materials that support optimal cell functionality. Furthermore, biofabrication of ‘living’ constructs has focused on achieving high cell viability, while in vitro cell differentiation and tissue maturation have received less attention. Current research efforts investigate a plethora of strategies with the potential to control stem cell line commitment. However, few of these aspects have been translated from basic 2D and 3D cultures into assessment of tissue formation within spatially-organised bioprinted constructs. This thesis aims to develop nanocomposite materials able to harness the bioactive properties and nanoscale interactions of metallic-ion based nanoparticles to grant commonly used polymeric biomaterials with superior capacity to stimulate skeletal tissue formation, and at the same time, tailor their physical properties to achieve improved ‘printability’ through biofabrication technologies. Firstly, a comprehensive literature review explores different emerging strategies utilising biofabrication technologies to create complex hybrid constructs and the role of composite bioinks, and biomaterial inks to overcome typical biomaterial limitations. Next, the results herein encompass the characterisation of metallic-ion based nanoparticles as suitable candidates to support hMSC viability and osteogenic differentiation in vitro. Subsequently, Mg-PCL was developed as a nanocomposite biomaterial ink that allowed high fidelity printing of support scaffolds with the capacity to stimulate mineralised matrix formation. Moreover, Sr-GelMA and LPN-GelMA were developed as multi-functional bioinks, achieving notable physical advantages over standard low-concentration GelMA, for the improved capacity for high fidelity printing of well-defined hMSC-laden constructs. Furthermore, the presence of Sr and LPN nanoparticles also enhanced osteogenic differentiation capacity of encapsulated hMSCs. In addition, LPN supported localisation of growth factors, thereby inducing host vasculature penetration and integration. Finally, the three systems were combined as a proof of concept for the convergent fabrication of a hybrid skeletal regenerative medicine construct. The multiple systems not only retained their advantageous properties, but their combination led to synergistic improvement of drug uptake and retention, and enhanced osteogenic differentiation of hMSCs and mineralised matrix formation. This ultimately highlights the promising potential of hybrid fabrication and the developed nanocomposite systems for skeletal regeneration.