Dibasic ammonium phosphate and phytic acid as alternative phosphate sources in sol-gel-derived 58S bioactive glass

• Phytic acid and diammonium hydrogen phosphate effectively incorporate phosphate during sol-gel synthesis, unlike triethyl phosphate. • In FIT samples, part of the phosphate segregates into crystalline phases, increasing silica‑network polymerization compared with FOS. • FOS samples contain phosphate groups with more non‑bridging oxygens, indicating predominantly terminal chain‑ending environments. • The absence of phosphate in TEP samples was not prohibitive to bioactivity, as hydroxyapatite formation still occurred. Phosphate incorporation into bioactive glasses during base-catalyzed sol–gel synthesis remains challenging when triethyl phosphate (TEP) is used as the phosphorus source. Several studies have reported incomplete phosphate retention and suboptimal P 2 O 5 content compared with levels typically obtained in melt-derived glasses. In this work, 58S bioactive glasses were synthesized by replacing TEP with phytic acid (FIT) and dibasic ammonium phosphate (FOS) to examine the chemical state of phosphate groups and their effects on structural properties and in vitro bioactivity. Glasses prepared with TEP, FIT, and FOS were characterized by X-ray fluorescence (XRF), thermogravimetric and differential thermal analyses (TG/DTA), nitrogen adsorption–desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and simulated body fluid immersion (Kokubo assay). Among the precursors tested, FOS enabled effective phosphate incorporation, achieving the nominal composition without forming segregated crystalline phases after heat treatment, and demonstrated superior bioactivity. FIT exhibited crystallization during heat treatment, which did not markedly affect bioactivity but may influence cellular responses. In contrast, TEP failed to incorporate phosphate at significant levels, yet still supported hydroxyapatite (HAp) formation during bioactivity assay.