Computational Methods in the Modeling of Scaffolds for Tissue Engineering - Computational Modeling in Tissue Engineering - page 104

cells are seeded on a porous scaffold that acts as a template to facilitate the
formation of functional new tissue and organ. Some variables such as pore size,
material type and fabrication process are known to influence the cell response [ 4 ].
A computational analysis of scaffold properties should consider the overall
problem as a continuous two phase's problem: a solid bulk scaffold and a fluid
medium inside the pores. The diversity of the methods used so far shows that
different assumptions have been made to simplify the complex experimental or
physiological conditions. Nevertheless the common aim of these studies is to
predict, understand or determine the optimal culture conditions or scaffold mor-
phology [ 5 ]. Mechanobiological concepts are also being used more commonly to
explain how the cells sense the signals from the environment and how their
response to them can affect the cell phenotype related processes. In this chapter,
we will discuss some of the results obtained with the computational methods used
to characterize the scaffold as an artificial structure to be used in tissue engineering
applications.
2 Computational Structural Characterization of Scaffolds
Generally, the conventional scaffold fabrication techniques (salt leaching, phase
separation or gas foaming) present difficulties to obtain a precise and repeatable
scaffold microstructure in which pore interconnectivity or pore size are guaranteed
[ 7 - 10 ]. Each technique is usually most suited to a specific biomaterial or scaffold
and for a specific tissue engineering application. Porous scaffolds need to be
characterized due to the irregular microstructures that give a different microen-
vironment to the cells attached onto the scaffold surface.
Novel techniques allow an initial computational control of fabrication using
computer-aided design (CAD). The common name used for these techniques is
rapid prototyping (RP). These techniques lead to better pore reproducibility of
regular shape and better interconnection than the conventional methods. Regular
scaffolds offer an easier understanding and optimization of diverse biological
phenomena. However, once fabrication using RP techniques is made, it is nec-
essary to characterize the regular pores because the accuracy of the fabrication
method depends on the biomaterial properties, the RP techniques used and the
conditions applied during the process [ 11 , 12 ].
In both cases (conventional and RP techniques) it is useful to characterize the
sample in a non destructive manner. Computationally it is possible to apply
imaging techniques (micro-Computed Tomography and Nuclear Magnetic Reso-
nance) and using reconstruction algorithms. Through scaffold reconstruction it is
possible to know the pore interconnectivity, the overall porosity, the pore size
distribution and the specific surface area. Some examples of scaffold structures
reconstructed and characterized using computational techniques are shown in
Fig. 2 . The irregular distribution of pores of calcium phosphate (CaP) cement
microstructure is shown in a cross section in Fig. 2 a[ 9 ]. The reconstruction was