Monolithic Glass Scaffolds with Dual Porosity Prepared by Polymer‐Induced Phase Separation and Sol–Gel

Abstract

Sol-gel-derived SiO 2 -CaO-P 2 O 5 porous glass monoliths with a dual hierarchical pore structure including both macropores of B20-200 micrometers and mesopores B5-20 nanometers in size are prepared in the presence of the drying control chemical additive formamide, for a possible application as scaffolds in bone tissue regeneration. While the mesopores are intrinsic to the sol-gel processing, the interconnected macropores are achieved through a polymer-induced phase separation together with the sol-gel transition, by adding a water-soluble polymer, poly(ethylene oxide), to the precursor sol. The textural nanopore structure is controlled through solvent exchange procedures and the addition of urea. The overall pore size distribution obtained by mercury intrusion porosimetry was found to shift to larger pore sizes when formamide is added. In vitro tests are used to evaluate the bioactivity. The cell-support function of the resultant scaffolds is also assessed in vitro using osteoblast-like cells cultured for 2 days. The results show that the scaffold has a significant bioactivity and a good ability to support the attachment of MC3T3 preosteoblast cells.

New bioactive glass scaffolds with exceptional qualities for bone tissue regeneration: response of osteoblasts and osteoclasts

“…To perform a careful analysis of the biological performance of TAMP material using advanced in vitro proliferation and differentiation assays, we produced circular, dual-porous disc shaped TAMP scaffolds of 70 mol% SiO 2 and 30 mol% CaO model composition with a diameter of approximately 13 mm and a height of approximately 2 mm, using a modified sol-gel fabrication procedure (figure 1(a)) [4,5]. TAMP scaffolds featured interconnected macro-pores ranging from 20 to 200 μm measured by mercury porosimetry and as seen in SEM micrograph in figure 1(b), and interconnected nano-pores ranging from 2.5 to 50 nm measured by BET nitrogen adsorption and imaged by SEM (see figure 1(c)).…”

“…BET analyses, revealed a surface area of 90.2±5.5 m 2 g −1 (figure 1(d)). Additionally, when incubated in simulated body fluid (SBF) or cell culture medium, TAMP scaffolds become coated with a crystalline layer of hydroxyapatite, which contributes to the glass' biocompatibility (figure 1(e)) [4,5]. Further, TAMP scaffolds dissolved with a half-life dissolution of 15.4 d under quasi-dynamic conditions [8].…”

“…To assess whether MC3T3-E1 pre-osteoblasts differentiate into mature osteoblasts when grown for extended periods on TAMP scaffolds, we quantitatively analyzed transcription of osteoblast differentiation-related genes (including genes related to [1] cell adhesion [labeled orange in figure 4(a)], [2] extracellular matrix and remodeling [light blue], [3] proliferation [olive], [4] differentiation [gray], [5] collagen expression [off red], [6] bone specific transcription regulation [yellow] and [7] expression of osteoblast calcified matrix-specific proteins [purple]) by quantitative PCR analyses (qRT-PCR) using a commercially 6) collagens (off red), and (7) osteoblast specific proteins (purple). (b) Expression profiles of proteins of these categories were analyzed by trend lines.…”

“…Although, many improvements have been made to the original Bio-glass® over the years (reviewed in [2]), a significant remaining drawback of Bioglass® is that it is a solid material that is not susceptible to cell penetration. We have developed a next-generation bioactive glass material termed tailored amorphous multi-porous (TAMP) that is highly porous, featuring interconnected macro-(20-200 μm diameter) and nanoporosity (2.5-50 nm), that not only allows cells to colonize the TAMP scaffolds and provide improved fluid exchange and significantly enlarged reactive surface area, but also to dissolve in biological fluids over time allowing its replacement by natural tissue [3][4][5][6][7][8]. The porosity of the TAMP creates a scaffold structure that mimics the natural structure of bone which is ideal for regenerating natural tissue [9][10][11].…”

“…Although we have reported previously on the characteristics and use of TAMP bioactive glass scaffolds [3][4][5][6][7][8], a thorough biological in vitro characterization using osteoblastic and osteoclastic cells has not been performed. In contrast to studies performed by others in which bioactive glass performance was judged by adding conditioned medium (medium exposed to glass) to cells [12,13,15,16], we seeded cells directly onto TAMP scaffolds without the addition of osteogenic medium for all analyses.…”