Tissue Engineering (TE) represents a smart approach aimed at repairing biological tissues by using biocompatible 3D scaffolds, which are able to support tissue ingrowth and regeneration either in vitro or in vivo. Currently, TE represents the main field of application of bioactive glasses (BGs) in clinical practice, since they perfectly fit into this landscape as material for the production of functional 3D porous architectures mimicking the trabecular morphology of cancellous bone.
Generally, BG scaffolds are produced by sintering of inorganic particles around a template acting as pore former (e.g. polymer sponge or particles), foaming processes or solid free-form fabrication technologies (SFF) (Rahaman et al. 2011).
Among these techniques, sponge replica method gained a foothold as the most effective and versatile strategy for the production of highly-reproducible and interconnected 3D architectures suitable for bone regeneration (Baino et al. 2015; Baino et al. 2011). Over time, several sacrificial templates have been employed, both of synthetic (i.e. commercial polyurethane sponges (Chen et al. 2006)) and natural (i.e. marine sponges (Baino et al. 2017)) origin.
The well-known flexibility of the method allowed our research team to think out of the box, proposing, for the first time, stale bread as new sacrificial template for the implementation of the method. SEM investigation performed on stale bread derived from waste of industrial companies revealed suitable structure for producing highly-sustainable bone TE scaffolds. Despite the different nature of the porous structure, it was observed that sourdough bread showed an open-cell architecture with pore size distribution and porosity percentage potentially able to allow tissue ingrowth and vascularization. Bread-derived scaffolds were then fabricated by using two different approaches, which involved the impregnation of the template either into a suspension of melt-derived glass particles (47.5SiO2-2.5P2O5-20CaO-10MgO-10Na2O-10K2O mol.%), thus obtaining macro-porous scaffolds, or into a sol leading to a binary mesoporous glass (60SiO2-40CaO mol.%). In the latter case, hierarchical scaffolds with porosity at the macro- and meso-scale were obtained.
SEM characterization and in vitro bioactivity tests were performed on both scaffold types and results were analyzed by using industrial polyurethane sponge-derived BG scaffolds as positive control.
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