Polyetheretherketone Titanium Composite implants: how surface morphology influences human osteosarcoma cell line growth

An outstanding property of bone tissue is its ability to regenerate. Fractures are indeed the most common large-organ, traumatic humans injuries. Bone wound healing process requires various endocrine growth factors and paracrine signal molecules, which are aimed at restoring homeostasis. The understanding of this finely regulated mechanism still represents one of the main challenges in bone tissue engineering. Reproducing bone microenvironment in medical devices, with biomaterials and additive manufacturing processes, allows an optimal solution for several orthopaedics problems. Spinal prosthesis, as well as hip and ankle prosthesis, are the most commonly encountered and still poorly solved issues. Fusion surgery is one of the standard treatments performed in patients with spinal stenosis, degenerative disc disease, spondylolisthesis or scoliosis. Several grafts materials have been used to research feasible solutions for such surgical treatment. Titanium and Polyetheretherketone (PEEK) have been proved to be the best candidates, as they have a high level of biocompatibility. However, both of them have advantages and disadvantages. In order to exceed the limitations associated with these surfaces, Orthofix® has produced an innovative orthopaedic device that included PEEK cores and porous titanium endplates. In such Polyetheretherketone Titanium Composite (PTC) implants, the Ti endplates are responsible for osteoconduction and cell adhesion, while the radiolucent PEEK central portion allows the plain radiographic determination of bone graft maturation. However, there are few published reports regarding PTC effectiveness. This thesis work wanted to fill some of these gaps by investigating how this PEEK/Titanium hybrid could influence Saos-2 adhesion and differentiation. Multiple sample groups obtained with different manufacturing process have been used in the process, and the potential lot-to-lot variation has been investigated. The thesis explains the development of different scaffolds’ morphologies, and it describes the adhesion and differentiation analyses performed. The collected data have been accurately reported, highlighting the effects of macro-, micro- and nano-metric morphological tuning of the scaffold surface on cells behaviour. The results suggested that cells are sensitive to specific surface topological features. However, further investigations with a longer period of time are still needed for a more in depth and comprehensive assessment of the system, especially regarding the nanometric surface changes.