A Survey of Methods for the Evaluation of Tissue Engineering Scaffold Permeability

Abstract

The performance of porous scaffolds for tissue engineering (TE) applications is evaluated, in general, in terms of porosity, pore size and distribution, and pore tortuosity. These descriptors are often confounding when they are applied to characterize transport phenomena within porous scaffolds. On the contrary, permeability is a more effective parameter in (1) estimating mass and species transport through the scaffold and (2) describing its topological features, thus allowing a better evaluation of the overall scaffold performance. However, the evaluation of TE scaffold permeability suffers of a lack of uniformity and standards in measurement and testing procedures which makes the comparison of results obtained in different laboratories unfeasible. In this review paper we summarize the most important features influencing TE scaffold permeability, linking them to the theoretical background. An overview of methods applied for TE scaffold permeability evaluation is given, presenting experimental test benches and computational methods applied (1) to integrate experimental measurements and (2) to support the TE scaffold design process. Both experimental and computational limitations in the permeability evaluation process are also discussed.

Experimental method to characterize the strain dependent permeability of tissue engineering scaffolds

“…This is not surprising since the porosity of the scaffolds in their study (ϕ4 95%) is much higher than our scaffolds (ϕ o70%). It is worth mentioning, according to the semi-empirical Kozeny-Carmen equation (Carman, 1956;Pennella et al, 2013), the permeability is a function of the porosity of the porous media.…”

“…The permeability k of the scaffold was calculated using Eq. (2) based on Darcy's law (Darcy et al, 1856;Pennella et al, 2013). …”

“…Different theoretical models have been developed to establish relationships between the strain and permeability for several tissues such as cartilage (interested reader is referred to (Lai and Mow, 1979;Lai et al, 1981;Holmes, 1985;Holmes and Mow, 1990)). While many experimental studies have been performed to measure the permeability of biological tissues and scaffolds (see (Pennella et al, 2013) for a review), only very few techniques have been developed to quantify the corresponding strain dependent permeability of the scaffolds. In a pioneer work, O'Brien et al (2007) developed an experimental set-up allowing to measure the permeability of highly porous natural polymeric scaffolds (porosity higher than 95%) under different strain conditions.…”

Applications of Computational Modelling and Simulation of Porous Medium in Tissue Engineering

“…The Darcy, Forchheimer, and Brinkman equations, which characterize fluid flow through porous scaffolds, require an important porous structure parameter, the permeability, κ. Sensitivity of model predictions are directly dependent on the accurate κ values, which depend on the geometric parameters of the pores in the scaffold [17]. In order to predict flow properties with high fidelity, determining the permeability using physical characteristics of the porous scaffold such as porosity and the pore shape is an approach.…”

Development of an Effective Cell Seeding Technique: Simulation, Implementation, and Analysis of Contributing Factors

“…The difficulty of characterizing some of these parameters is the reason why it is difficult to find all of them in publications. 30 In practice, permeability is an overarching 31 for functional TE applications. In correlation with the study of Melchels et al, 4 our results indicated direct influence of permeability on CSE and uniformity.…”