Highly degradable porous melt-derived bioactive glass foam scaffolds for bone regeneration

Abstract

a b s t r a c tA challenge in using bioactive melt-derived glass in bone regeneration is to produce scaffolds with interconnected pores while maintaining the amorphous nature of the glass and its associated bioactivity. Here we introduce a method for creating porous melt-derived bioactive glass foam scaffolds with low silica content and report in vitro and preliminary in vivo data. The gel-cast foaming process was adapted, employing temperature controlled gelation of gelatin, rather than the in situ acrylic polymerisation used previously. To form a 3D construct from melt derived glasses, particles must be fused via thermal processing, termed sintering. The original Bioglass Ò 45S5 composition crystallises upon sintering, altering its bioactivity, due to the temperature difference between the glass transition temperature and the crystallisation onset being small. Here, we optimised and compared scaffolds from three glass compositions, ICIE16, PSrBG and 13-93, which were selected due to their widened sintering windows. Amorphous scaffolds with modal pore interconnect diameters between 100-150 mm and porosities of 75% had compressive strengths of 3.4 ± 0.3 MPa, 8.4 ± 0.8 MPa and 15.3 ± 1.8 MPa, for ICIE16, PSrBG and 13-93 respectively. These porosities and compressive strength values are within the range of cancellous bone, and greater than previously reported foamed scaffolds. Dental pulp stem cells attached to the scaffold surfaces during in vitro culture and were viable. In vivo, the scaffolds were found to regenerate bone in a rabbit model according to X-ray micro tomography imaging. Statement of SignificanceThis manuscript describes a new method for making scaffolds from bioactive glasses using highly bioactive glass compositions. The glass compositions have lower silica content that those that have been previously made into amorphous scaffolds and they have been designed to have similar network connectivity to that of the original (and commercially used) 45S5 Bioglass. The aim was to match Bioglass' bioactivity. The scaffolds retain the amorphous nature of bioactive glass while having an open pore structure and compressive strength similar to porous bone (the original 45S5 Bioglass crystallises during sintering, which can cause reduced bioactivity or instability).The new scaffolds showed unexpectedly rapid bone regeneration in a rabbit model.

Bioactive glass containing 90% SiO 2 in hard tissue engineering: An in vitro and in vivo characterization study

“…In accordance with our in vivo data, other studies have already shown successful results of BG grafting (Detsch et al, ; Wu et al, ; Xynos et al, ; Zhang et al, ) and with similar resorbable characteristics (Nommeots‐Nomm et al, ). As far as we know, this is the first time that BGs have been grafted using the tibia defect model comparing six different experimental times, which clearly shows the native physiology of the tibia bone.…”

“…Bioactive glass (BG) scaffolds, with a suitable interconnected porous structure similar to that of trabecular bone, have the potential to aid the regeneration process by giving cells a temporary template to grow into (Nommeots-Nomm et al, 2017) while presenting unique characteristics, such as robustness, loading capacity, and bioactivity (Aznar et al, 2016;Giménez et al, 2015). Therefore, chemical signals delivered from BGs, mainly ionic products, have been widely reported to promote matrix synthesis of fibroblasts and angiogenic differentiation of endothelial cells (Gorustovich, Roether, & Boccaccini, 2010;Shih, Lu, Hsieh, Chen, & Chen, 2014).…”

Sintering and concomitant crystallization of bioactive glasses

“…This, however, did not coincide with a larger temperature range between T SE and T CO or between T g and T CO , and thus does not seem to indicate improved processing here. Although glass ICIE16 is known to show significantly better processing at higher temperatures than 45S5 and also has a much higher CaO content, both seemed to crystallize to the same phase (Figure F), possibly because of their similarity in network connectivity . The only difference was that the reflections were better resolved for glass ICIE16 (as well as for glass F0‐F8), while for example the two peaks at 33.5 and 34.5°2 θ overlapped for 45S5.…”

The effect of serum proteins on apatite growth for 45S5 Bioglass and common sol-gel derived glass in SBF

“…Comparing the XRD patterns of BG ( Figure 1a) and TG ( Figure 1b) following immersion in pSBF, HA peaks did not appear for the TG glass until 7 day, compared to 1 day for BG, and the intensity and sharpness were less than for BG. Slower HCA formation on TG could be due to the larger concentration of silica (network formers) in TG than BG, which resulted in a higher network connectivity (mean number of bridging Si-O-Si bonds per silicon atom) of TG (2.62 [16]) than BG (1.90 [20,21]). The lower network connectivity of BG could enhance cation exchange increased the medium pH, which in turn improved Ca/P compound deposition.…”