Bioactive glasses in the system CaO–B 2 O 3 –P 2 O 5 : Preparation, structural study and in vitro evaluation A. Saranti, I. Koutselas 1 , M.A. Karakassides * Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece Received 26 July 2005; received in revised form 29 November 2005 Abstract Glasses in the system x B 2 O 3 (1  x)[y CaO P 2 O 5 ], (x = 0, 0.1, 0.2, 0.3, y = 2, 2.6, 3, 4, 5) have been prepared by fast quenching of high temperature melts. The presence of B 2 O 3 affected the glass forming ability, allowing the preparation of calcium phosphate glasses with y P 2.6. The structure of glasses was analyzed by l-Raman and infrared spectroscopy. The analysis indicated that the glass network is dominated by highly charged species from phosphate tetrahedra with 3 (pyro) or 4 (ortho) NBOs, while the boron atoms are incorpo- rated mainly in 3 coordinated sites in the form of BB 3 or BB 2 O  units. A small fraction of B£  4 units was also evident from the spectra analysis of glasses with high CaO content. All calcium borophosphate glasses exhibited bioactivity after soaking in SBF solution within a few days. This was observed by l-Raman and SEM microscopy, while XRD patterns clearly revealed growth of hydroxyapatite phase. The presence of boron in the glass network has a catalytic effect at favoring bioactivity of the otherwise bioinert calcium phosphate glasses. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Bioglass; Raman spectra; Glass structure; Phosphate glasses 1. Introduction Calcium phosphate based glasses and glass–ceramics have been of interest for medical uses due to their unique properties. In particular, a bioactive calcium phosphate based-implant after integration with bone forms a biologi- cally active hydroxycarbonate apatite layer at the bone/ implant interface which favors bonding with bone and soft tissues. The first reported bioglass and one of the most common and well-characterized is the 45S5 Bioglass (45 wt%SiO 2 , 24.5CaO, 6P 2 O 5 and 24.5Na 2 O) [1]. After this, a variety of similar glasses and glass–ceramics were developed but all with the following key compositional fea- tures: SiO 2 content smaller than 60 mol%, high Na 2 O and CaO content and high CaO/P 2 O 5 ratio [2]. Addition of B 2 O 3 , CaF 2 , MgO or TiO 2 generally leads to glass–ceramic materials which also show bioactivity [3–7]. In addition, phosphate based glasses seem to be also used as bioresour- cable materials because of their solubility [8,9]. These degradable and absorbable by the human body glasses are useful as suture thread in bone fracture fixation appli- cations, as dental implants and as carriers in drug delivery [10–12]. However, almost all bioactive glass-based materi- als contain a large amount of silica. The development of new glass–ceramics biomaterials has recently concentrated on SiO 2 -free glasses. It is well accepted that phosphate glasses without silica and with high CaO/P 2 O 5 molar ratio (>1.5) have a high potential for use as biomaterials because their chemical composition is close to that of natural bone [13]. However, it is not easy to prepare these glasses since very high temperatures are required and have often the tendency to crystallize. For instance, preparation of calcium phosphate glasses in the pyro- or orthophosphate region (CaO/P 2 O 5  2 or 3) has been achieved only by using large amounts of other oxides, 0022-3093/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2006.01.042 * Corresponding author. Tel.: +302 6510 97276; fax: +302 6510 97074. E-mail address: mkarakas@cc.uoi.gr (M.A. Karakassides). 1 Present address: Department of Materials Science, School of Natural Sciences, University of Patras, 26504 Patras, Greece. www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 352 (2006) 390–398