Influence of textural characteristics on biomineralization behavior of mesoporous SiO2-P2O5-CaO bioactive glass and glass-ceramics

Abstract

The present work demonstrates the novel synthesis of multi-components, ternary SiO2-P2O5-CaO mesoporous bioactive glass (MBG) and bioactive glass-ceramics (MBGC) through acid assisted sol-gel route by using Pluronic, P123 as structure directing agent followed by evaporation induced self-assembly (EISA) process. As synthesized samples has been characterized by different analytical techniques before and after immersion in physiological solution to unravel the structural, morphological and textural properties and correlate with biomineralization process. The different structural species of the pristine MBG/MBGC samples have been confirmed by high resolution x-ray diffraction (HR-XRD) and Fourier transforms infra-red (FTIR) spectroscopy studies. Bright field transmission electron microscopy (BF TEM) study reveal a wormhole like structures in the pristine samples, which is a typical characteristic of mesoporous samples. Moreover, the obtained samples exhibit superior textural characteristics like enhanced surface area and mesoporosity revealed by nitrogen adsorption-desorption technique. The presence of various anionic species in the pristine samples has been revealed by magic angle spinning nuclear magnetic resonance (MAS NMR) technique. The textural characteristics and the biomineralization behavior of pristine and soaked samples have been studied by varying the calcium and phosphorous contents with respect to silica. The in-vitro bioactivity analysis performed over three different samples in simulated body fluid (SBF) for different immersion duration leads to the formation of hydroxy carbonated apatite (HCA). The formed HCA layer is confirmed by analytical techniques such as HR-XRD and FTIR spectroscopy, which indicates the nano sized HCA crystals are impregnated in the amorphous matrix. Furthermore, significant modifications on the surface of samples have been illustrated by FE-SEM micrographs before and after SBF immersion, which specifies growth of thin-HCA layer. The mesostructured glassy samples showed an excellent cell viability response without toxicity up to the concentration of 100 mg ml−1. Additionally, cell-culture studies like cell-proliferation and cell viability test were also performed on the MBG and MBGC to show the material-cell interaction and it was found to be in good agreement within the desired range.