IN HONOR OF LARRY HENCH Effects of boron oxide substitution on the structure and bioactivity of SrO-containing bioactive glasses Xiaonan Lu 1 , Lu Deng 1 , Po-Hsuen Kuo 1 , Mengguo Ren 1 , Ian Buterbaugh 1 , and Jincheng Du 1, * 1 Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA Received: 28 September 2016 Accepted: 24 January 2017 Ó Springer Science+Business Media New York 2017 ABSTRACT B 2 O 3 /SiO 2 substitution in 55S4.3 bioactive glasses with 5 mol% of SrO has been synthesized and characterized to understand their structure and bioactivity as a function of composition by combining experimental and computer simulation techniques. Raman spectrometry, X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR) were utilized to characterize the structural changes induced by boron content and to identify the formation of hydroxyapatite (HAp). In vitro bioactivity tests were performed in simulated body fluid with a fixed glass mass to solution volume ratio and a particle size range. Needle-like HAp was found to form on the surface of the 55S4.3 with SrO sample from scanning electron microscopy and confirmed from XRD and FTIR. In addition to the experimental efforts, these glasses were also simulated using classical molecular dynamics simulations with partial charge potentials and recently developed parameters for boron oxide to understand their short- and medium- range structures. The glasses from simulations were analyzed in terms of the local structure around the glass network formers, especially the boron coordi- nation number, and found to agree well with theoretical models. The medium- range structural information such as Q n distribution and network connectivity was also obtained and used to understand the compositional dependence of property and bioactivity. The results show that additional boron oxide increased the network connectivity of the 55S4.3 glass and inhibited or delayed the for- mation of HAp in vitro. Introduction Unlike earlier generations of biomaterials that are biologically inert and compatible, bioactive glasses, first introduced by Prof. Larry Hench about five dec- ades ago, can elicit specific biological responses at the interface with host tissue due to a bond formation through the growth of an interfacial layer of hydrox- yapatite (HAp) [1, 2]. These bioactive glasses consist of four components: Na 2 O–CaO–P 2 O 5 –SiO 2 , and their bioactivity was found to strongly depend on the glass composition. The first, and probably still one of the most, bioactive glass composition is 45S5 (46.1SiO 2 – 24.4Na 2 O–26.9CaO–2.6P 2 O 5 in mol%) [1]. The 55S4.3 Address correspondence to E-mail: Du@unt.edu DOI 10.1007/s10853-017-0836-9 J Mater Sci In Honor of Larry Hench