Environmental Technology & Innovation 18 (2020) 100647 Contents lists available at ScienceDirect Environmental Technology & Innovation journal homepage: www.elsevier.com/locate/eti Synthesis of bioactive material by sol–gel process utilizing polymorphic calcium carbonate precipitate and their direct and indirect in-vitro cytotoxicity analysis Manish Kumar a , Edgard Gnansounou b , Indu Shekhar Thakur a,∗ a School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India b Bioenergy and Energy Planning Research Group (BPE), IIC, ENAC, Station 18, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland article info Article history: Received 4 December 2018 Received in revised form 2 January 2020 Accepted 20 January 2020 Available online 23 January 2020 Keywords: Bioactive glass Sol–gel process Calcite Cytotoxicity Hydroxyapatite abstract To mitigate the rising level of CO 2 , biological method of CO 2 sequestration is one of the effective methods. Chemolithotrophic microbes are able to fix atmospheric CO 2 and precipitated polymorphic minerals like calcite, vaterite and aragonite. Based on this, bioactive glass was synthesized by sol–gel process using polymorphic calcium carbon- ate mineral precipitated by chemolithotrophic Serratia sp. ISTD04. Characterization of bioactive material and its bioactivity was evaluated by SEM, EDX, FT-IR, XRD, ICP-MS. SEM analysis revealed biomaterial showing more bioactivity due to deposition of smaller particle like appearance throughout the surface. FT-IR analysis of sintered and immersed bioactive material indicated presence of O-Ca-O, O-Si-O and Si-O-Si functional group. The XRD analysis indicated important features similar to melt-derived Na 2 O-containing glass ceramics like formation of crystalline phase Na 2 Ca 2 Si 3 O 9 . Further in-vitro study was performed in simulated body fluid (SBF) and on osteosarcoma cell line, confirmed that material and their supernatant did not reflect any cytotoxicity. © 2020 Elsevier B.V. All rights reserved. 1. Introduction The carbon dioxide (CO 2 ), one of the most potent greenhouse gas (GHG), its concentrations (270 ppm) was stable before the industrial revolution, now it is increased to 400 ppm (Kumar et al., 2018; Kumar and Thakur, 2018). It has been expected that by the middle of current century CO 2 concentrations should be reach up to 600 ppm, and by the end it is probably 700 ppm (Kumar et al., 2017a; Thakur et al., 2018). There is penalty of biological methods available to reduce the atmospheric CO 2 (Kaplan and Reinhold, 1999; Kumar et al., 2017b, 2016a). Fixation of CO 2 by biological and physicochemical methods resulted formation of carbonate mineral in the form of calcite, magnesite and dolomite (Kumar et al., 2016b; Srivastava et al., 2015a). Mostly, the bacterial species can precipitate carbonate minerals in different environmental (growth condition) such as salinity, alkalinity, duration and media composition (Knorre and Krumbein, 2000; Rivadeneyra et al., 2004; Srivastava et al., 2015b). This microbial precipitated carbonate minerals could be used as raw material for synthesis of bioactive glasses similar to, CaCO 3 extracted from eggshell waste for synthesis of calcium magnesium silicate (Choudhary et al., 2015). Bioactive glasses belong to a group of bioactive materials; extensively used in the medical fields such as dentistry and orthopedics (Abbasi et al., 2015). A material can be called as bioactive if they are able to produce biological response and ∗ Corresponding author. E-mail addresses: manishkumar.bt@gmail.com (M. Kumar), edgard.gnansounou@epfl.ch (E. Gnansounou), isthakur@hotmail.com (I.S. Thakur). https://doi.org/10.1016/j.eti.2020.100647 2352-1864/© 2020 Elsevier B.V. All rights reserved.