Permeability evaluation of 45S5 Bioglass®-based scaffolds for bone tissue engineering

Fabrication of CaO–NaO–SiO2/TiO2 scaffolds for surgical applications

“…Porosity of the ScC was at 87 % which is lower than both the Ti containing scaffolds at 89 % (Sc1) and 93 % (Sc2). A high degree of porosity ([90 %) has been cited in the literature as a preferential attribute for scaffold fabrication [4,29,30] as the porosity of trabecular bone is cited in the range of 80-90 % [30]. The porosity of these scaffolds was quantified by surface area analysis where the ScC produced the highest surface area (3.3) which corresponds to the lower value determined for the porosity.…”

Bioactive glass and glass-ceramic scaffolds for bone tissue engineering

“…However, higher scaffold porosity results in diminished mechanical properties thereby setting an upper functional limit for pore size and porosity. Thus, a balance must be reached depending on the repair, rate of remodeling and rate of degradation of the scaffold material [74], and the scaffold design has to consider an optimal porosity enabling sufficiently high permeability (i.e., pore interconnectivity, see discussion in §3.1) for waste removal and nutrient supply and adequate stiffness and strength (see §3.1, Figure 7, Figure 9) to sustain the loads transmitted to the scaffold from the surrounding healthy bone [95]. Furthermore, scaffolds should be amenable to fabrication in complex or irregular shapes in order to match specific defect morphologies in bone of individual patients.…”

“…Recent developments related to bone TE try to bridge this gap and overcome this problem by architectures and components carefully designed from comprehensive levels, i.e., from the macro-, meso-, micrometer down to the nanometer scale [101], including both multifunctional bioactive glass composite structures (see §3.2) and advanced bioactive glass-ceramic scaffolds exhibiting oriented microstructures, controlled porosity and directional mechanical properties [99,[102][103][104][105], as discussed in the following paragraphs. Most studies have investigated mainly the mechanical properties, in vitro and cell biological behavior of glass-ceramic scaffolds [13][14][15]30,43,52,94,95,97,99,, as summarized in Table 1, and scaffolds with compressive strength [99,102] and elastic modulus values [99,105] in magnitudes far above that of cancellous bone and close to the lower limit of cortical bone have been realized. Fu et al [99] fabricated bioactive glass (13-93) scaffolds with oriented (i.e., columnar and lamellar) microstructures and found that at an equivalent porosity of 55-60%, the columnar scaffolds had a compressive strength of 25 ± 3 MPa, compressive modulus of 1.2 GPa, and pore width of 90-110 µm, compared to values of 10 ± 2 MPa, 0.4 GPa, and 20-30 μm, respectively, for the lamellar scaffolds.…”

“…In the complex process of bone regeneration, scaffold microstructure and microstructure anisotropy play important roles because both morphological features determine the spatial distribution of the newly formed tissue [143]. The sophisticated hierarchical micro-structure of bone with highly interconnected trabeculae ensures waste removal, nutrient/oxygen supply and protein transport during tissue regeneration and bone growth [95,144]. Because studies have shown that cell growth into a scaffold depends on how well nutrients can permeate through the porous structure [145,146], the permeability of scaffolds, a property directly related to the degree of pore interconnectivity, is a key factor influencing the scaffolds ability to enhance bone tissue regeneration [95].…”

“…To our knowledge, there are only a few studies on the permeability assessment/evaluation of porous bioceramic scaffolds including both numerical modeling [147] and experimental determination of permeability constants [95,145,148,149]. In a recent study on bioactive glass-ceramic scaffolds confirming that the fabricated scaffolds had transport properties as well as pore structure close to trabecular bone.…”