Preparation and in vitro evaluation of bioactive glass (13–93) scaffolds with oriented microstructures for repair and regeneration of load‐bearing bones

Abstract

Bioactive glass (13-93) scaffolds with oriented microstructures, referred to as 'columnar' and 'lamellar', were prepared by unidirectional freezing of suspensions, and evaluated in vitro for potential use in the repair and regeneration of load-bearing bones in vivo. Both groups of scaffolds showed an 'elastic-plastic' mechanical response in compression, large strain for failure (>20%), and strain rate sensitivity, but the columnar scaffolds had the additional advantages of higher strength and larger pore width. At the equivalent porosity (55-60%) and deformation rate (0.5 mm/min), the columnar scaffolds had a compressive strength of 25 +/- 3 MPa, elastic modulus of 1.2 GPa, and pore width of 90-110 microm, compared to values of 10 +/- 2 MPa, 0.4 GPa, and 20-30 microm, respectively, for the lamellar scaffolds. Cellular response to the scaffolds was evaluated using murine MLO-A5 cells, an osteogenic cell line. While the cellular response to both groups of scaffolds was better than control wells, the columnar scaffolds with the larger pore width provided the most favorable substrate for cell proliferation and function. These results indicate that 13-93 bioactive glass scaffolds with the columnar microstructure could be used for the repair and regeneration of load-bearing bones in vivo.

Bioactive glass and glass-ceramic scaffolds for bone tissue engineering

“…However, the brittleness and low fracture toughness remain a major impediment of these materials. The limited strength and low fracture toughness (i.e., ability to resist fracture when a crack is present) of bioactive glasses has so far prevented their use for load-bearing implants [8,70,96,98], and thus the repair and regeneration of large bone defects at load-bearing anatomical sites (e.g., limbs) remains a clinical/orthopedic challenge [99,100]. 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.…”

“…The limited strength and low fracture toughness (i.e., ability to resist fracture when a crack is present) of bioactive glasses has so far prevented their use for load-bearing implants [8,70,96,98], and thus the repair and regeneration of large bone defects at load-bearing anatomical sites (e.g., limbs) remains a clinical/orthopedic challenge [99,100]. 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.…”

“…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.…”

“…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 addition to providing excellent in vitro bioactivity [14,43,94,109,110,115], cell biology behavior [15,105,114,118,119] and favorable mechanical properties [99,102,105], bioactive glassceramic scaffolds have shown superior in vivo behavior (e.g., bone formation, mineralization, higher interfacial strength between implant and bone) compared to the glass in particulate form [113] or compared to other bioactive materials (HA, tricalcium phosphate) [52].…”