Rational Design of Artificial Cellular Niches for Tissue Engineering - Tissue Engineering: Computer Modeling, Biofabrication and Cell Behavior - page 138

Fig. 5 Elasto-plastic
response of an electrospun
scaffold measured empirically
by tensile test ( circles )andin
silico predicted using a
poly-line/spring model ( solid
line )[ 72 ]
show a certain mechanical response to stimulate the proliferation of cells until the
newly regenerated tissue is formed.
The use of finite element method for predicting the mechanical properties of
rapid-prototyping-produced scaffolds is straightforward, as these microstructures
are usually simple, with well-defined geometries [ 77 ]. Simulating microstructures
produced by electrospinning, however, becomes much more complex, as fibers are
randomly located. Due to scaffolds random morphologies, it would be very inaccu-
rate to work with a small representative volume element (RVE); conversely, large
RVEs must be used. This implies that such entities cannot be handled in an efficient
way using finite element codes by average-performance computers. New smarter
models have been recently proposed to solve this problem, where electrospun mi-
crostructures are handled as poly-lines [ 72 , 78 ]. These models replace the poly-line
by a sequence of springs, assuming that the spring constant describes the elastic
modulus of the polymer; they also use a “bond angle potential” to reproduce its
flexural stiffness. Results obtained using this model for non-woven porous scaffold
have been able to perfectly match empirical measurements, as shown in Fig. 5 .
4.2.2 Perfusion/Vascularization
Cell proliferation inside a porous scaffold needs for an adequate supply of oxygen
and nutrients; and vascularization of a scaffold involves cell migration. Therefore,
any realistic computational model used in Tissue Engineering should implement dif-
fusion of oxygen, nutrients, wastes, etc. throughout the physiological medium that
wets the entire scaffold. This requirement makes necessary to study and understand
diffusion through a scaffold.
Very important properties, such as porosity, pressure drop or permeability, will
change depending on scaffold microstructure. Several authors have developed dif-
ferent 3D models to infer the dependence of such properties from geometric cues.
Usually all these studies have been conducted using standard computational fluid
dynamics (CFD) environments, such as Fluent [ 73 , 79 , 80 ]. Recently, other authors
have also used similar models to design and optimize microfluidic assays combin-
ing 2D and 3D cell cultures [ 81 ]. Lately, some other authors have developed even