Altering the pH during sol-gel synthesis of bioactive glass particles and its effect on structural and antibacterial properties

Abstract

In sol-gel glass chemistry, the pH of the sol directly influences the rate of the hydrolysis and condensation reactions, leading to changes in the glass’s structural properties and potentially altering its function as a biomaterial. This research used various acidic pH values, 2, 3, 3.65, 5, and 5.65, to create sol-gel bioactive glass with a 45SiO₂-14.5NaO₂-14.5CaO-6P₂O₅-10ZnO-5CuO-5CoO mol% composition. A pH of 2 allowed for increased surface area, 26.23 m²/g, and cumulative surface area of pores, 34.78 m²/g, compared to the other pH values used. Raman spectroscopy highlighted variances in the intensity of Q² and Q³ species, with a pH of 2 and 3.65 having a higher intensity of Q³ species. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) revealed that the concentration of Cu²⁺ ions released from the glass network in simulated body fluid (SBF) was the highest after 1000 h of incubation for the pH 3.65 glass, 100 mg/L, which translated to the most significant inhibition of E. coli after 48 h of contact. Elemental, thermal, and structural analysis using energy dispersive X-ray spectroscopy, differential thermal analysis, Fourier-Transform Infrared Spectroscopy, and X-ray diffraction was also performed, with no discernible relationship found between changing the pH of the sol used to synthesize these glasses.