Micro-CT analysis of sea sponge pore architecture as a model of a cell-populated synthetic tissue scaffold

Sponges consist of a tissue skeleton that provides structure for its elaborate pore system of canals and chambers. Sponges have been noted for their remarkable ability to support cellular life within these pores. For that reason, their structure is of great interest to us since our goal is to create a scaffold that supports cell vitality beyond diffusion depth from the scaffold surface. In the sponge this is achieved by convective transport of nutrients through the pore system. Hence, understanding of the architecture of sea sponges has the potential to aid in the production of better design of porous, cell-populated, synthetic tissue scaffolds. Pore geometry affects depth and distribution of the solute transport needed to sustain the cells lining the pores. To explore this aspect we need accurate 3D measurements of pore architecture and interconnectivity. Three-dimensional micro-CT imaging can be used to characterize the desired microarchitecture labyrinthine pore structure of a sea sponge. The sea sponge was collected, dried, and then rotated in small angular measurements inside the scanner as an x-ray image was obtained at each angle of view. Reconstructed cross-sectional images of the sponge consisted of up to 107 cubic voxels, 20μm on a side. After reconstruction, Analyze 8.1 was used to display and generate measurements of the sponge's pores. The pores were subjected to a sequence of morphological erosion and dilation operations, each of which either removed or added one layer of voxels from the outer surface of the segmented pore. Hence, each erosion removed 40μm from the diameter of a pore. Progressive erosions were used to calculate pore volume and to disconnect pores from adjacent pores, thereby identifying connecting throats(s) as well as their diameter. Along with diameter, individual pore volume and surface area were also computed. Results show that the throats were predominately 264±129μm in diameter. Preliminary data show complex pore structures can be analyzed with morphological erosion and dilation image analysis techniques to provide significant quantitative data. Such data has provided information about throat identification and diameter, as well as pore volume and surface area. Ground work has also been laid for computing flow path of least resistance through the pore labyrinth from any point in the labyrinth.