Biomimetic Materials for Engineering Stem Cells and Tissues - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 325

heart, nerve, liver, etc. But only a few successful tissue grafts have been
developed so far for clinical use. For example, Apligraf® was the fi rst
tissue engineered skin substitute approved by the US Food and Drug
Administration (FDA). Studies on synthetic scaffolds seeded with spe-
cialized cells have proved the ability of the scaffold to aid in adhesion,
proliferation, migration, orientation and continued functions of the cells
[2, 3]. Recently the focus has shifted from using specialized cells to stem
cells that have the ability to self-renew indefi nitely and differentiate into
specialized cells with the right cues [4]. In order to study the behavior of
stem cells on synthetic scaffolds and to develop an ideal tissue graft, there
still remain many properties of the scaffold that need to be optimized.
Hence it is important to engineer the properties of the synthetic scaffold
such that it would mimic the native microenvironment of the host tissue
that is to be repaired. For example, biomineralization is a biological pro-
cess that involves the nucleation and growth of minerals within a matrix
of bone ECM proteins during bone remodeling [5]. To mimic the process
of biomineralization, scaffolds comprised of collagen and hydroxyapatite
(HA) have been developed for bone applications [3, 6-8].
The concept of biomimetics to engineer stem cells and tissues would be
the convenient way to come up with a successful graft, as it involves simu-
lating their native microenvironment, thereby supporting cellular functions
and tissue regeneration. Biomimetics is a bottom-up approach that involves
engineering of tissue building blocks, assembling them into complex tissue
analogs, and the creation of tissue engineered organs. The purpose of the
bottom-up tissue engineering approach is to accurately determine the local-
ization of the biological components of corresponding tissue or organ, and
to understand the mechanism of their biological functional process and the
complex signaling pathways underlying tissue organization. In this way,
it would be possible to engineer the stem cells and tissues to develop a
successful tissue graft. Of particular interest, impact of stem cell behaviors
such as adhesion, proliferation, migration, and differentiation onto the bio-
mimetically-developed nanofi ber scaffolds will be discussed in this chap-
ter in the context of tissue engineering and regeneration. The methods of
fabrication of biomimetic materials and the surface modifi cation of these
materials for better cellular recognition are also discussed.

14.2 Fabrication of Biomimetic Materials

For stem cells and tissue engineering applications, fabrication of biomi-
metic materials, in other words the scaffolds, involve the mimicking of
native ECM in terms of all structural and functional features that sup-
port the cell growth and function. Such biomimetic scaffolds should be
porous, possess the required mechanical stability, should be suitably