Biomimetic Materials for Engineering Stem Cells and Tissues - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 326

functionalized and possess a large surface area with structural features as
present in vivo [9]. Many attempts have been made to fabricate the scaffolds
for tissue engineering applications but none fulfi ll all the requirements
of an engineered physiologically functional tissue. Therefore develop-
ment of biomimetic materials is of great importance. Biomimetic scaf-
folds can be made up of hydrogels, nanofi bers, porous materials, proteins
and other biomolecules. Most of the proteins making up the ECM exhibit
abundant nanometer-scale structures such as fi brils, ridges, grooves, pil-
lars and pits that are hypothesized to contribute to cell-matrix signaling
[10]. Nanotopography is also present in individual ECM molecules, such
as collagen molecules, which are approximately 300 nm long and 1.5 nm
wide. These molecules can form fi brils that extend for tens of micrometers
in length and have diameters between 260 and 410 nm. In order to mimic
the native ECM, it is therefore necessary to fabricate nanofi ber scaffolds
for most of the cell and tissue engineering applications [11]. In the follow-
ing section, we further focus on biomimetic nanofi bers developed through
widely used techniques such as electrospinning, electrospray, phase sepa-
ration and self-assembly.

14.2.1 Electrospinning

Electrospinning is the technique that is practiced most frequently for
making nanofi ber scaffolds. The basic equipment setup includes a syringe
pump, fi ber collector, and a high-voltage power system as shown in
Figure 14.1. When a polymer solution is forced through a capillary hole,
it forms a drop at the needle tip due to surface tension. A high voltage is

High voltage
power supply

Polyme
solution

Syringe

Nanofiber

Polymer jet
(stable region)

Instability
region

Syringe pump

Counter electrode
(fiber collector)

Figure 14.1 Schematic representation of electrospinning setup.