Biologically relevant phosphate-based nanostructures: interactions with soft matter and biomedical applications

This work of thesis deals with the physico-chemical investigation of biologically-relevant calcium and magnesium phosphate-based nanostructures. The motivation of this work relies on the evidence that these materials constitute the main inorganic components of human body, where they are present in several locations and fulfill a great number of functions. The study of their formation in bio-relevant conditions is thus noteworthy, as it could contribute both to unravel the in vivo formation mechanisms, as well as to guide in the design of tailored materials for biomedical applications. In this thesis, we mainly focused on two recently-discovered systems, which are amorphous magnesium-calcium phosphate nanoparticles (AMCPs) present in mammalians’ gut and magnesium phosphate-based bone cements (MPCs). As far as the first topic is concerned, we aimed at studying the formation of synthetic analogs of AMCPs in conditions mimicking to a certain extent the in vivo milieu, with the ultimate goal of connecting the physico-chemical findings with the physiological and pathological role of AMCPs, given their involvement at the immune level. We inspected the effect of pH and Mg2+ on the lifetime of the amorphous phase, and we investigated how representative molecules belonging to soft matter, present in the gut and in simulated intestinal fluids, affect the formation and the features of AMCPs. We also investigated the possibility of including bio-relevant proteins within the inorganic structure. In all these case studies, the particles were characterized by means of a multi-technique approach, which allowed us to obtain a complete physico-chemical overview of the system. Aiming at assessing the potentialities of phosphate-based nanostructures for biomedical applications, we chose to focus our attention on MPCs, which are a new category of bone cements whose features still need to be completely established. These materials, which are obtained upon the mixing of a powder component and an aqueous-based solution, were assessed in terms of cohesion, setting time, crystallinity, microstructure and mechanical properties. We characterized how these properties change according to formulation parameters and due to the inclusion of citrate and polymeric additives. These investigations demonstrate our ability to tune the features of these cements, making them effective candidates for orthopedic applications.