Optimization Approaches for the Design of Additively Manufactured Scaffolds - Tissue Engineering: Computer Modeling, Biofabrication and Cell Behavior - page 111

In the last decade, technologies for the preparation of biomaterial scaffolds benefited
from the development of several additive manufacturing (AM) techniques, which
allowed the production of free-form porous scaffolds with custom-tailored architec-
tures that can be easily derived from solid models obtained, for example, from di-
agnostic medical imaging. Among the AM techniques most commonly used in TE,
we can include: selective laser sintering (SLS), stereolithography (SLA), extrusion-
based techniques (e.g. fused deposition modeling, precision extrusion deposition)
and three dimensional printing (3DP) [ 1 ]. These techniques have been widely in-
vestigated for the processing of thermoplastic biopolymers into structures with con-
trolled shape and tailored porosity and have been successfully applied for the prepa-
ration of several scaffolds for different applications, such as bone TE [ 2 , 3 ] repair of
osteochondral defects [ 4 - 6 ], and lumbar interbody fusion implants [ 7 ].
Advances introduced by AM techniques have significantly improved the ability
to control scaffold architecture (size, shape, interconnectivity, geometry, and orien-
tation), yielding to biomimetic structures with different design and material compo-
sitions, thereby enhancing control over their mechanical properties, biological ef-
fects, and degradation kinetics. Integration of AM with medical imaging techniques
has allowed the production of scaffolds that are customized in size and shape for
specific applications or even for individual patients.
The use of computer-based technologies in TE has quickly evolved into the de-
velopment of a new field, named Computer-Aided Tissue Engineering (CATE). It
can be defined as the application of enabling computer-aided technologies, includ-
ing computer-aided design (CAD), image processing, computer-aided manufactur-
ing (CAM), and rapid prototyping (RP) for modeling, designing, simulating, and
manufacturing biological tissue and organ substitutes. Taking advantage from these
tools, scaffold design, intended as the selection of material and micro-architecture
proper for a specific application, has gained growing interest within TE. The central
role of scaffold microstructure in determining the functionality of both the construct
and the newly grown tissue, has been clearly demonstrated [ 8 , 9 ]. Thus, research ef-
forts are moving towards the development of innovative methods for the generation
of scaffold architectures optimized on the basis of application-specific biological
and mechanical requirements. In this context, Finite Element Analysis (FEA) has
played a main role in the reduction of experimental tests and costs required by in
vitro and in vivo research.
The present chapter gives an overview of the methods for the design of additively
manufactured scaffolds and their applicability in TE. Along with a survey of the
state of the art, the Authors will also present a recently developed method, called
load-adaptive scaffold architecturing (LASA) , which is based on the finite element
calculation of the stress field at the scaffold site on the basis of an imposed load
system.
2 Scaffold Design and Optimization
Several approaches have been described in the literature for the design of scaf-
folds with subject-specific external shapes along with controlled internal micro-