Rational Design of Artificial Cellular Niches for Tissue Engineering - Tissue Engineering: Computer Modeling, Biofabrication and Cell Behavior - page 139

Fig. 6 Degradation of a
PCL/TCP scaffold
empirically measured by Lam
et al. ( boxes ) and predicted by
Erkizia et al. ( solid line )
more complex mathematical models, using a set of coupled non-linear ordinary dif-
ferential equations, which describe the evolution of the different tissue constituents
inside scaffolds [ 82 ].
4.2.3 Scaffold Degradation/Drug Release
One of the main aims of Tissue Engineering consists in replacing the artificial scaf-
fold with natural tissue. This replacement requires degradation of the scaffold to be
timely compatible with the rate of tissue neo-formation.
For this reason, several authors have empirically measured and computer-
modeled scaffold degradation rate. Using different 3D techniques, they have devel-
oped degradation models of additively-manufactured [ 83 ] and electrospun scaffolds
[ 84 ], and even degradation of spherical particles [ 85 , 86 ]. Figure 6 shows the degra-
dation profile of an additively-manufactured scaffold as documented in Erkizia et
al. [ 83 ].
In some cases it is interesting to introduce substances in the scaffold that will in-
teract with the surrounding natural tissue, such as drugs, growth factors or vaccines.
In these cases, the above-mentioned molecules are not released instantaneously but
in a controlled manner, as the scaffold degrades.
This has also been the object of investigations by several authors who have faced
these issues from many different perspectives. Some of the first one-dimensional
models developed in the late '70s and early '80s were simple mathematical models
that considered the diffusion from the surface of cylinders or spheres that contained
a homogeneous distribution of drug inside [ 87 , 88 ]. Nowadays, 3D models devel-
oped for degradation studies are capable to reproduce release profiles in real scaf-
folds. Using these models, it is possible to infer the influence of geometrical features
such as fibers geometry or drug localization on the overall drug-release profile [ 89 ].