The permeability of a three-dimensional biomaterial is a crucial parameter in order to determine the feasibility of such material to be used to manufacture tissue engineering scaffolds.
In general, the permeability of the scaffold has a strong influence on several aspects:
Nutrients and oxygen supply
The permeability of a material is closely related to the suitability of the scaffold to host cells since it is related to the microstructure and determines how easy or difficult is to get nutrients and oxygen for those cell living inside the scaffold. Intuitively, nutrient and O2 supply will be more difficult in those scaffolds with a very low permeability.
Viability of long-term cultures
The permeability of a scaffold is a parameter which may be nicely used to estimate cell development in a long-term experiment. In this sort of experiments, cells are cultivated for long periods of time aiming them to develop and to remodel the environment by generating the extra-cellular matrix that composes the desired engineered tissue as, e.g.. osseous matrix.
Obviously, cell proliferation and matrix generation have a very important effect on the original scaffold porosity since matter deposition usually leads to a decrease in the overall scaffold permeability. Therefore, an excessive cell proliferation may cause the pore occlusion and the interruption of the supplies to the cell in the inner part of the scaffold.
Scaffold porosity under deformations states
All the tissues are subject to mechanical loads in-vivo and, therefore, scaffolds on which cells are grown should also be ready to hosts living cell populations under mechanical loads causing them noticeable deformations. A typical example consists of a porous scaffold for osseous cells culture which, once implanted, should stand for the loads associated to, e.g., normal gait.
Deformations associated to those loads may have a strong influence on the scaffold micro-structure, since pores shape and size might be modified causing a reduction of the scaffold permeability. Thus, the measurement of permeability in deformed states is a nice tool in the study of the suitability of scaffolds under noticeable deformations.
These reasons make of porosity an important parameter, frequently provided by the scaffold manufacturers, whose effect of the cell populations have been deeply studied in the literature.
The EBERS TEB series in combinations with the P3D chambers allow determining the permeability of a porous scaffold by means of a simple experiment. A feasible experimental set-up feasible for this purpose is shown below.
The experimental set-up depicted on the right side may be used to measure the permeability of a scaffold subjected to perfusion flow.
The physical principle used for this purposed is based on the measurement of the pressure drop caused by the introduction of the scaffolds in the culture medium flow. Thereby, the scaffold permeability can be easily determined by applying simple mathematical relations.
Adding a pressure sensor to control the pressure drop in the culture chamber allows estimating the permeability of the scaffold is the only additional equipment necessary for this experiment.