Bioactive scaffolds for bone regeneration: a surface science approach

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Despite recent improvement in biomaterials for orthopedic applications, we are still far from the dream of an implant that substitutes large bone defects and slowly degrades to leave in place new bone generated by the patient's body. This is the long term objective of the present program, together with a detailed understanding of the process of bone mineralization. To achieve it, my research team will synthesize and characterize bioactive scaffolds made of a biodegradable polymeric matrix and bioactive glass (BG). The polymeric matrix ensures mechanical stability to the implant and BG promotes precipitation of hydroxyl carbonate apatite (HCA, the inorganic component of bones), and bone regrowth around the implant. We will test the scaffolds in simulated body fluids (SBFs) at increasing levels of complexity, starting from solutions that reproduce only the ionic composition of body fluids, and then adding proteins and finally cells. Our results will provide a link between in-vitro and in-vivo reactivity of biomaterials, which is missing at the moment, and shed light on the ongoing debate concerning which SBF represents better the phenomena occurring in-vivo. We will use an array of spectroscopic, calorimetric and microscopic techniques to analyze the changes occurring at the interface between the scaffolds' surface and the body fluids. This is a crucial region, which determines the mechanical stability and the integration of the implant in the body. Finally, we will functionalize the surface of the scaffolds with oligopeptides that enhance cell adhesion or promote HCA precipitation, with the goal of implanting the scaffolds without pre-seeding them with external stem cells or osteoblasts, since the patient's own cells will be attracted by these biological cues. The successful achievement of this research program will deliver a next generation bioactive scaffolds, elucidate the process of bone mineralization around them, develop surface-sensitive techniques to test their reactivity in SBFs, and provide needed guidelines about SBFs useful to predict biomaterials behaviour in-vivo.