Comprehensive assessment of bioactive glass and glass-ceramic scaffold permeability: experimental measurements by pressure wave drop, modelling and computed tomography-based analysis

Elisa Fiume; Alessandro Schiavi; Gissur Orlygsson; Cristina Bignardi; Enrica Verné; Francesco Baino

doi:10.1016/j.actbio.2020.10.027

Comprehensive assessment of bioactive glass and glass-ceramic scaffold permeability: experimental measurements by pressure wave drop, modelling and computed tomography-based analysis

Acta Biomater. 2021 Jan 1:119:405-418. doi: 10.1016/j.actbio.2020.10.027. Epub 2020 Oct 20.

Authors

Elisa Fiume¹, Alessandro Schiavi², Gissur Orlygsson³, Cristina Bignardi⁴, Enrica Verné⁵, Francesco Baino⁶

Affiliations

¹ Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 Turin, Italy; Department of Mechanical and Aerospace Engineering (DIMEAS), Politecnico di Torino, 10129 Turin, Italy.
² National Institute of Metrological Research (INRiM), Applied Metrology and Engineering Division, 10135 Turin, Italy.
³ Department of Materials, Biotechnology and Energy, Innovation Center Iceland (ICI), 112 Reykjavik, Iceland.
⁴ Department of Mechanical and Aerospace Engineering (DIMEAS), Politecnico di Torino, 10129 Turin, Italy.
⁵ Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 Turin, Italy.
⁶ Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 Turin, Italy. Electronic address: francesco.baino@polito.it.

PMID: 33091624
DOI: 10.1016/j.actbio.2020.10.027

Abstract

Proper microstructural and transport properties are fundamental requirements for a suitable scaffold design and realization in tissue engineering applications. Scaffold microstructure (i.e. pore size, shape and distribution) and transport properties (i.e. intrinsic permeability), are commonly recognized as the key parameters related to the biological performance, such as cell attachment, penetration depth and tissue vascularization. While pore characteristics are relatively easy to asses, accurate and reliable evaluation of permeability still remains a challenge. In the present study, the microstructural properties of foam-replicated bioactive glass-derived scaffolds (basic composition 47.5SiO₂-2.5P₂O₅-20CaO-10MgO-10Na₂O-10K₂O mol.%) were determined as function of the sintering temperature within the range 600-850°C, identified on the basis of thermal analyses that were previously performed on the material. Scaffolds with total porosity between 55 and 84 vol.% and trabecular-like architecture were obtained, with pore morphological features varying according to the sintering temperature. Mathematical modelling, supported by micro-computed tomography (μ-CT) imaging, was implemented to selectively investigate the effect of different pore features on intrinsic permeability, which was determined by laminar airflow alternating pressure wave drop measurements and found to be within 0.051-2.811·10^-10 m². The calculated effective porosity of the scaffolds was in the range of 46 to 66 vol.%, while the average pore diameter assessed by μ-CT varied between 220 and 780 μm, where the values in the lower range were observed for higher sintering temperatures (750-850°C). Experimental results were critically discussed by means of a robust statistical analysis. Finally, the complete microstructural characterization of the scaffolds was achieved by applying the general constitutive equation based on Forchheimer's theory.

Keywords: Bioactive glass; Bone tissue engineering; Permeability; Porosity; Scaffold.

MeSH terms

Ceramics
Glass*
Permeability
Porosity
Tissue Engineering
Tissue Scaffolds*
X-Ray Microtomography