Pore size evaluation of direct-dissolution salt-leached 3D silk fibroin scaffold using microcomputed tomography

Abstract

Performance of direct-dissolution salt-leached silk fibroin scaffold for tissue engineering is heavily influenced by its microarchitecture as it affects cell – scaffold interaction, hence the importance of evaluating pore size three dimensionally. Pore size measurement using scanning electron microscopy (SEM) is not practical as the evaluation is destructive and only gives information along 2D cross-sectional area. Microcomputed tomography (micro-CT) was preferred as it is non-destructive and able to give three-dimensional information but it lacks contrast and the specimen requires a minimum thickness to be evaluated. This experiment was aimed to evaluate direct-dissolution salt-leached scaffold pore size using micro-CT using the right threshold setting and specimen thickness. Threshold was determined by comparing micro-CT images from scaffolds made with salt particles of size 158 µm to 503 µm to their respective scanning electron microscopy (SEM) results using ImageJ. Minimum specimen thickness was determined from the relationship between average pore sizes measured for every specimen thickness, evaluated using CTAn software. Using threshold and thickness obtained, pore size can be determined by CTAn. Threshold was determined to be Threshold = (0.0566 x salt particle size) – 2.7536. Ratio of minimum specimen thickness to salt particle size used to evaluate scaffold is 3.5. Pore sizes for scaffolds made with salt particles of size 158 µm, 250 µm, 378 µm, and 503 µm are found to be 86.3 µm, 174.7 µm, 321.9 µm, and 425.9 µm, respectively. Pore size of scaffold made by salt leaching method can be predicted with equation of pore size = (0.919x salt particle size) – 45.327.