Systematic evaluation of the osteogenic capacity of low-melting bioactive glass-reinforced 45S5 Bioglass porous scaffolds in rabbit femoral defects

Abstract

Due to the low strength and high brittleness of 45S5 Bioglass®, it is still a great challenge for the three-dimensional porous 45S5 Bioglass® to treat mechanically required loaded bone defects. Therefore, 45S5 Bioglass®-derived bioactive glass-ceramic (BGC) porous scaffolds were fabricated at a low temperature sintering condition with and without the addition of 4% low-melting ZnO/B2O3 (ZB) bioactive glass as a reinforcing agent and using 350- or 500 μm paraffin microspheres as a porogen. The pore structure characterization for the scaffolds indicated that the scaffolds containing 4% ZB had very good macroporous structures of ∼313 and ∼448 μm in pore size and over 70% porosity with appreciable strength (>15 MPa), which was about four times higher than that those manufactured without ZB and with 350 μm porogen scaffolds. The open porosity was decreased with the addition of 4% ZB but the interconnected pore percentage (>50 μm) was increased with increasing the porogen size from 350 to 500 μm. In vivo investigations revealed that the stronger scaffolds containing 4% ZB and 500 μm porogen were particularly beneficial for osteogenic capacity in critical size femoral bone defects, accompanied with an accelerated bone ingrowth (6–18 weeks) and the material itself experiencing mild resorption. In contrast, both the scaffolds with smaller pore sizes exhibited a low level of new bone ingrowth (<32%) after 6–12 weeks implantation. These results suggest a promising application of such 45S5 Bioglass®-derived BGC scaffolds in a clinical setting, especially for mechanically loaded bone defects.