3D longitudinal characterization of swelling in Alginate/Hydroxyapatite scaffolds

It is of paramount importance for a scaffold to preserve its shape and mechanical stability for a prolonged time. While an initial swelling is desirable because the resulting increase in pore- and throat-size facilitates cell attachment and growth, an uncontrolled swelling would lead to a reduced mechanical integrity and to a compressive stress toward the surrounding tissue. Thanks to non-destructive and three-dimensional (3D) computed microtomography (μ-CT), it is possible to characterize and monitor the wettability and the swelling processes through time. With additional image analysis, it is also possible to quantitatively assess the alterations induced by the liquid in the whole 3D domain. This allows for a better understanding of the structural and functional properties of the considered tissue engineering scaffolds. This approach has been here applied to nanocomposite Alginate/Hydroxyapatite scaffolds for bone tissue engineering aged in simulated body fluid (SBF). The same sample has been scanned at several time points (up to 60 days) with a conventional X-ray micro-focus benchtop system. The resulting voxel size is 8.33 μm. The reconstructed volumes have been then co-registered in 3D with respect to the baseline (first volume of the time series) in order to measure the swelling through time. A total volume dilatation of about 10% was recorded and the maximum swelling was observed after 10 days of embedding. After 18 days an erosion process started to corrode the walls leading to a slight contraction of the construct.