VASCONCELOS, H.C., COUTINHO, R., FREIRE, P., FARIAS, A.C., GONÇALVES, M.C., SILVA PINTO, A. (2018) - Bioglass Prepared via a Mineral Water-Assisted Sol-Gel Route. In: Perez, M., Mills, J. (eds.) Archipelagos, Types Characteristics and Conservation, Series Earth Sciences in the 21st century, Nova Science Publishers, ISBN: 978-1-53614-681-3: 71-104. ​

​Furnas Volcano (São Miguel Island), in the Azores archipelago, became popular in the early nineteenth century for its mineral water sources used for medicinal purposes. Furnas has several sources of thermal waters all highly ionized with pH values ranging from highly acidic to alkaline. These qualities make the Furnas mineral water ideal for the sol-gel synthesis of ceramics and glass with the added benefits of being both a reactant and catalyst for this chemical process. In the 1960s, Hench first introduced bioactive glass to be used in bone implants. Due to frequent corrosion exhibited by the metals of the first generation of biomaterials, Bioglass 45S5® and other bioactive glass began to be developed and soon attracted the attention of many researchers. This is mostly due to its ability to establish more efficient biological and mechanical connections with bone tissue by forming a layer of carbonated hydroxyapatite (HCA) on the surface. The structure and composition of glass can host a wide range of metallic ions which dictate its bioactivity. When liberated these ions can mediate bone regeneration. Because in the sol-gel process the precursor materials are in water, the incorporation of metal ions is generally easier providing for a wide range of compositions and direct doping ions for therapeutic purposes. This chapter discusses a new paradigm in the sol-gel synthesis, particularly in the synthesis of bioactive glass. In this new approach the deionized water is replaced (in the hydrolysis step) by highly ionized and naturally acidified thermal water collected from springs located in Furnas Volcano. Given the potential impact of these waters on the structure and bioactivity of sol-gel bioactive glass, special emphasis was given to their genesis, physicochemical properties and ionic diversity. To conclude we present a case study on the synthesis and characterization of bioactive glass (45S5, 58S and 77S systems) using several types of thermal waters with the respective chemistry shown in a Piper diagram.