Synchrotron X-Ray Computational Tomography of Fibrous Scaffolds for Morphological Characterisation

Cell behaviour and tissue development are inherently sensitive to morphological features of tissue-engineered scaffolds. Traditionally, imaging techniques such as SEM, TEM, AFM, and CLSM provide high-resolution 2D images to characterise scaffold morphology. However, these techniques have poor penetration and low resolution transversely to the sliced planes. In contrast, synchrotron radiation X-ray micro-computed tomography (SR-µCT) enables 3-D imaging of large volumes with submicron isotropic resolution. We used SR-µCT at beamline I13-2 (Diamond Light Source) to image jet-sprayed nonwoven fibrous scaffolds used in the Harefield Valve, both with and without human adipose-derived stem cells preserved in ethanol to maintain native wet conditions. Large-volume imaging was achieved by stitching 2x2 tiled datasets and reconstructing them into 1 mm³ volumes at 0.325 µm voxel size, enabling clear scaffold. The scaffold exhibited a layered, transversely isotropic structure, with additional in-plane anisotropy observed when using high-speed drum fabrication. SR-µCT revealed significantly higher scaffold porosity compared to SEM analysis, which consistently underestimates porosity due to limited depth and connectivity information. Cell distribution and morphology showed that cells preferentially adhered and proliferated along in-plane structures at full scaffold colonisation. We hypothesise that the cells minimise energy expenditure by expanding in directions of least resistance.