 Scaffold pore connectivity

Scaffold pore connectivity describes how void spaces in a tissue-engineering scaffold communicate with one another and with the exterior. It affects which regions are accessible to fluid, transported substances and migrating cells. Porosity gives the amount of void space, whereas connectivity describes its arrangement. Two scaffolds with the same porosity can contain either communicating channels or isolated cavities.

A useful idealization represents pores as vertices of a graph and communicating throats as edges. Label the pores reached from an inlet by flood fill or another graph traversal. One explicitly defined accessibility measure isIf seven equal-volume pores out of ten communicate with the inlet, $C_{\mathrm{in}}=0.7$. That does not establish through-flow: the connected region must also reach an outlet. A large inlet-accessible dead-end region can have the same $C_{\mathrm{in}}$ as a region that spans the specimen.

The size of a passage also matters. A throat can pass a small dissolved molecule while excluding a larger rigid probe. An accessibility analysis can therefore specify both a boundary and a probe diameter. Actual cells can deform and interact with surfaces, so a rigid-probe geometry calculation is a model of access, not a complete prediction of cell migration.

Micro-computed tomography provides three-dimensional structural data for such questions. Michael J. Moore and colleagues published a quantitative scaffold-interconnectivity method using this approach.^[ref] After image segmentation separates solid and void, the connectivity result depends on resolution and the rule used to connect neighboring image elements. Apparent diagonal contact in an image does not necessarily establish a finite open throat.

A transport experiment supplies complementary evidence. Apply a stated pressure difference, measure flow and compare with the imaged pathways. A connected scaffold can still have low intrinsic permeability because narrow throats restrict transport. Reporting porosity, an explicitly defined connectivity measure and a flow measurement therefore answers three related but distinct questions.