Bioactive Glass from Eggshells and Silica Oxide Obtained by Mechanical Milling: Characterization and Bioactivity Tests

Abstract

This study details the synthesis and characterization of a bioactive and biocompatible bioglass designed for biomedical applications, particularly in the repair and regeneration of damaged bone tissue. The bioglass was synthesized by combining calcium oxide (CaO), sustainably sourced from eggshells, and silicon oxide (SiO₂), the latter produced using the Stöber method, which enables the production of silica particles with high purity, controlled size, and uniform morphology, essential characteristics for ensuring the material's bioactivity and stability. The synthesis of SiO₂ by this method involves the hydrolysis and condensation of precursors such as tetraethyl orthosilicate (TEOS) in an alcoholic medium with ammonia as a catalyst. The combination of these materials was carried out using mechanical milling and melting processes. Mechanical milling, conducted for 6 h, improved the mixture homogeneity, reduced particle size, and lowered the material's melting temperature, facilitating its processing. The synthesized bioglass was characterized using advanced analytical techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). The bioactivity was evaluated by immersion in simulated body fluid (SBF), and the results indicated the formation of calcium phosphates, confirming the material bioactivity and its potential for favorable interactions with biological tissues post-implantation. Additionally, a cytotoxicity assay was performed using the MTT method, in which the bioglass dispersed in a polymeric matrix was evaluated. The results demonstrated biocompatibility starting from the seventh day of cell contact, evidencing cell viability and the absence of significant cytotoxic effects. This research highlights the importance of integrating natural and synthetic sources in biomaterial development, emphasizing the key role of mechanical milling, melting, and the use of high-purity SiO₂ in optimizing the properties of bioglass for biomedical applications.