Deeper Insights into a Bioactive Glass Nanoparticle Synthesis Protocol To Control Its Morphology, Dispersibility, and Composition

Abstract

The aim of this study was to investigate the effect of three synthesis parameters on the morphology and composition of nanosized binary bioactive glass particles (nBGPs) obtained through a modified Stöber process. Syntheses were conducted by varying only one parameter at a time while keeping the other parameters constant. As already mentioned in the literature, the ammonium hydroxide volume conditioned the size of the nanoparticles. Nonagglomerated monodispersed spherical particles with a diameter between 70 and 452 nm were produced. The quantity of calcium nitrate and the moment it was introduced in the sol had a tremendous impact on the quantity of calcium inserted and on the particle morphology and aggregation state. High Ca-content particles were obtained when the calcium precursor addition time was 1 h or less after the beginning of the sol–gel reaction but at the cost of a strong aggregation. A better control on the morphology, polydispersity and dispersibility of the nBGPs was achieved when the Ca(NO 3 ) 2 addition time was increased up to 6 h. However, a significant decrease of the quantity of Ca 2+ inserted was also noticed. Using an intermediate (3 h) addition time, the quantity of calcium nitrate has been optimized to maximize the insertion of Ca 2+ ions inside the silica particles. Finally, an optimum initial Ca/Si atomic ratio of 2, maximizing Ca insertion while limiting the salt quantity used, was found. It led to the synthesis of particles with a molar composition of 0.9SiO 2 –0.1CaO without any side effect on the particle stability and morphological characteristics.

Unravelling the Impact of Calcium Content on the Bioactivity of Sol–Gel-Derived Bioactive Glass Nanoparticles

“…However, the following calcium salt addition can promote aggregation and morphology inhomogeneity, as mentioned in our previous study. 28 Indeed, aggregated particles are obtained when Ca(NO 3 ) 2 is added at H ≤ 1h. We assume that for such an early Ca salt addition time, the silica particles are not fully formed yet.…”

“…Note that as in the study of De Oliveira et al 27 , our previous study showed that the nominal and the actual composition of BGNs differ greatly. 28 Therefore, the objective of this work is to unravel the impact of calcium content upon the bioactivity of BG nanoparticles, while keeping the specific surface area unchanged. To do so, binary BGNs with different compositions have been obtained through a modification of the Stöber process.…”

Protein Adsorption on SiO2-CaO Bioactive Glass Nanoparticles with Controllable Ca Content

“…However, the actual concentration of incorporated CaO was lower than the nominal CaO concentration in these particles. Such a gap between nominal and actual compositions of BGNs has also been reported in the literature [7][8][9]. Given the concentration-dependent therapeutic effects of biologically active ions, precise control over the amount of incorporated CaO is crucial as it is directly related to the ion-released behavior.…”

“…BGNs are usually synthesized using sol-gel processing, a wet chemistry route involving the hydrolysis and condensation of alkoxide precursors (typically tetraethyl orthosilicate) [1]. By varying the sol-gel processing parameters (e.g., the molar ratio of precursors and catalysts), the size, chemical composition, and textural properties of BGNs can be controlled [7][8][9][10][11]. The composition significantly influences the structure and properties of glasses [12].…”

Elaboration of Superparamagnetic and Bioactive Multicore–Shell Nanoparticles (γ-Fe2O3@SiO2-CaO): A Promising Material for Bone Cancer Treatment

“…About 57% of the initial Ca 2+ ions have been incorporated in the glass network, an insertion rate consistent with our previous findings. 37…”