Lizette Morejón Alonso a , José Ángel Delgado García-Menocal a , Maite García-Vallés b , Salvador Martínez Manent b , Elizabeth Rosado Balmayor c , Martijn van Griensven c a Center of Biomaterials, University of Havana, Havana, Cuba b Faculty of Earth Sciences, University of Barcelona, Barcelona, Spain c Technical University of Munich, Munich, Germany Exploring the use of silica sands and calcite from natural deposits to prepare bioactive glasses Paper presented at the \VII International Congress of Biomaterials, BIOMAT’18", 14 – 16 March 2018, Havana, Cuba Nowadays bioactive glasses represent one of the most suc- cessful bioceramics used for bone tissue restorations. In this work, three types of silica sands (White, Yellow and Gray sands) and calcite from Cuban natural deposits were em- ployed to synthesize glasses from the system SiO 2 –CaO– Na 2 O. The ions released from glasses were evaluated through in vitro tests in Tris-HCl and in simulated body fluids. All sands had purity around 99.2 % of SiO 2 and con- tained traces (ppm) of Zr, Cr, Ba, Ce and Sr ions, while cal- cite raw material had traces of Sr, Cr, Zr, Ce and Zn. All glasses induced a pH change in Tris-HCl from 7.4 to 9 after 24 h; they had similar ion-release behavior in the in vitro solutions tested and showed a significant bioactive perfor- mance after 5 h. This work illustrates the potentialities of the use of natural resources to develop medical products when recognized trademark materials are not available. Keywords: Bioactive glasses; Natural raw sources; Bioac- tivity; Silica sands 1. Introduction The high incidence of bone injuries due to pathologies or traumas that are reported today by national or international health organizations depicts a challenging medical problem for many surgical services around the world [1 – 4]. Some bone diseases lead directly to pain or deformity, but others are \silent" disorders until they cause fractures [5]. Injuries of bone tissues can disable and/or impair temporally or per- manently the overall style of life of patients and can even put peoples’ lives at severe risk. These circumstances at- tract the attention of researchers from different branches of knowledge, including surgeons, hospital institutions and health system managers in multiple countries. The usual management of this type of lesions involves surgical treat- ments that enable the restoration of osseous tissues, which implies significant healthcare resource utilization and hos- pital costs [6 – 8]. Bioactive glasses constitute at present one of the most studied biomaterials as bone substitute materials [9]. Their ability to bond intimately to bone through a layer of hydro- xycarbonateapatite (HCA) during the osseointegration pro- cess favors the rapid restoration of the bone bed and makes them suitable for a wide variety of clinical applications [10]. The exchange of ions that occurs between medical glasses and body fluids determines both the speed at which biodegradation occurs and its extent. The mechanism that explains the stages by which the HCA layer is generated in silicate-based glass formulations has been described by Hench et al. from Bioglass â 45S5 bioactive glass studies [11, 12]. Bioglass â 45S5 has been used in multiple clinical applications since the 1980s with encouraging results [13]. Based on the excellent osseointegration behavior of the sili- cate-based glasses, a wide diversity of bioactive glass for- mulations has been investigated with the purpose of adjust- ing their biodegradation rate at the speed of natural bone restoration processes and to satisfy the requirements of spe- cific clinical applications. However, in developing countries commercialized medi- cal products (as recognized bioactive glasses), are not al- ways available. Facing the imperious clinical necessity of the employment of synthetic biomaterials for bone tissue restorations in severe bone lesions, national health systems develop domestic formulations and study new routes to ob- tain medical products. For example, a major drawback in large-scale production of bioactive glasses by sol-gel is the high cost of the standard silica precursor, usually tetraethyl orthosilicate (TEOS). In order to evade this problem Adams et al. [14] describe a novel sol-gel preparation of 45S5 bioactive glass using diatom biosilica from cultured cells of the diatom, Aulacoseira granulata as substitute for TEOS, and in another work, proposes a bioactive glass in the quaternary system SiO 2 –Na 2 O–CaO–P 2 O 5 from Niger- ian sand as the silica source [15]. Additional studies have been targeted to develop bioactive glass ceramics com- posed of SiO 2 –CaO–Na 2 O using rice husk ash waste mate- rial as a natural source of silica [16, 17]. This work explores the use of Cuban natural resources to obtain silicate-based glasses that can be used for the re- storation of injuries of the skeletal system and that can be accessible to the national health system. The usefulness of silica sands that are extracted from the Santa Teresa deposit IJMR_MK111716 – 8.10.18/reemers L. M. Alonso et al.: Exploring the use of silica sands and calcite from natural deposits to prepare bioactive glasses 1 galley proof