Effect of Calcium Precursor on the Bioactivity and Biocompatibility of Sol-Gel-Derived Glasses

Abstract

This study investigated the impact of different calcium reagents on the morphology, composition, bioactivity and biocompatibility of two-component (CaO-SiO2) glasses produced by the Stöber process with respect to their potential application in guided tissue regeneration (GTR) membranes for periodontal repair. The properties of the binary glasses were compared with those of pure silica Stöber particles. The direct addition of calcium chloride (CC), calcium nitrate (CN), calcium methoxide (CM) or calcium ethoxide (CE) at 5 mol % with respect to tetraethyl orthosilicate in the reagent mixture gave rise to textured, micron-sized aggregates rather than monodispersed ~500 nm spheres obtained from the pure silica Stöber synthesis. The broadening of the Si-O-Si band at ~1100 cm−1 in the infrared spectra of the calcium-doped glasses indicated that the silicate network was depolymerised by the incorporation of Ca2+ ions and energy dispersive X-ray analysis revealed that, in all cases, the Ca:Si ratios were significantly lower than the nominal value of 0.05. The distribution of Ca2+ ions was also found to be highly inhomogeneous in the methoxide-derived glass. All samples released soluble silica species on exposure to simulated body fluid, although only calcium-doped glasses exhibited in vitro bioactivity via the formation of hydroxyapatite. The biocompatibilities of model chitosan-glass GTR membranes were assessed using human MG63 osteosarcoma cells and were found to be of the order: CN < pure silica ≈ CC << CM ≈ CE. Calcium nitrate is the most commonly reported precursor for the sol-gel synthesis of bioactive glasses; however, the incomplete removal of nitrate ions during washing compromised the cytocompatibility of the resulting glass. The superior bioactivity and biocompatibility of the alkoxide-derived glasses is attributed to their ease of dissolution and lack of residual toxic anions. Overall, calcium ethoxide was found to be the preferred precursor with respect to extent of calcium-incorporation, homogeneity, bioactivity and biocompatibility.

Hydroxyl Groups Induce Bioactivity in Silica/Chitosan Aerogels Designed for Bone Tissue Engineering. In Vitro Model for the Assessment of Osteoblasts Behavior

“…As shown in detail (Figure 12), actin-immunolabeled osteoblasts are efficiently grown on the SCS8 aerogel with cell polarization, elongation, and significant expression of stress fibers, which has been described previously by us and others as a marker of cell adhesion and differentiation due to their role in cytoskeletal rearrangement [32][33][34]. The seeding has resulted in a regular dispersion of cells, which initially approach the material pieces, and after 72 h in culture, start to differentiate into branched cells, with osteocyte-like prolongations approaching the material present in the well, displaying long, thin cell processes extending from a small, rounded cell body throughout the experiment duration, as shown for 1-week cells, which proliferate and migrate to cover the scaffold surface.…”

“…As shown in detail (Figure 12), actin-immunolabeled osteoblasts are efficiently grown on the SCS8 aerogel with cell polarization, elongation, and significant expression of stress fibers, which has been described previously by us and others as a marker of cell adhesion and differentiation due to their role in cytoskeletal rearrangement [32][33][34]. On the spread of cells, quite a number of FAs are located in the center of the cell, as shown in the controls, with circular morphology and small size.…”

“…FAs play a role in the process of surface recognition, with subsequent cell adhesion and mechanotransduction-induced changes in osteoblastic cells. When the nanoscaled biomaterial surface is chemically attractive, additional cues for cell positioning, spreading, and differentiation can be achieved [32,35,[46][47][48]. The improved characteristic in our scaffold properties, which are appropriate porosity, pore structure, and pore size of the scaffold, have demonstrated a positive effect on cell adhesion, with focal adhesion recruitment and development and initial osteoblasts differentiation.…”

Impact of Bi2O3 and ZrO2 Radiopacifiers on the Early Hydration and C–S–H Gel Structure of White Portland Cement

“…Experimental and computational studies have demonstrated that lower Ca/Si ratios give rise to higher MCLs in Portland cements [22,34]. In fact, this is a common occurrence in many calcium silicate systems, as calcium ions are widely acknowledged to depolymerize the silicate structures of glasses, minerals, and ceramics [22,35].…”

Iodoform-Blended Portland Cement for Dentistry

“…Human osteosarcoma cells are commonly employed for the initial biocompatibility appraisal of biomaterials for dental and orthopaedic tissue treatment [41,42]. In the present study, the cytocompatibility of WPC and WPC-I towards MG63 human osteosarcoma cells was assessed using an MTT assay [41,42]. The results of this in vitro biocompatibility assessment are presented in Table 4.…”