Bivalent cationic ions doped bioactive glasses: the influence of magnesium, zinc, strontium and copper on the physical and biological properties

Bioactive glass and glass ceramic materials are widely used as substitutes for bone augmentation and restoration, in orthopaedic, dental and maxillofacial surgery and in the tissue engineering field. Indeed, these materials are bioactive, biocompatible, mechanically stable, biodegradable and favour osteointegration, being able to promote bone tissue formation at their surface and to bond to surrounding living tissues when implanted in the human body. It has been demonstrated that bioglass (BG) ionic dissolution products (e.g. Si, Ca, P and Na) are able to induce and stimulate the expressions of genes related to the osteoblastic differentiation and bone formation, to stimulate angiogenesis in vitro and in vivo, as well as to play possible antibacterial and anti-inflammatory actions. Thus, it is possible to tailor BGs properties properly formulating their chemical composition and adding selected ions with specific functional and biological role. In this perspective, Hench proposed a new generation of genetically designed glasses, on the basis of their ability to activate specific genes involved in in situ tissue regeneration, by doping silicate and phosphate glasses with several active ions, particularly metallic ions with therapeutic effects. In this framework, the present review is aimed to provide an overview about the effect of selected cationic substitutions (i.e. magnesium, zinc, strontium and copper), incorporated within the bioglasses structure, on the physical and biological properties of these materials, since the comprehension of the influence of the most employed metallic ions has to be considered pivotal to address the formulation of more promising and performing glasses.