Biomedical Engineering Reference
In-Depth Information
Fig. 3
Scanning electron microscope images of Matrigel and designed self-assembling peptide
nanofi ber scaffold. (
a
) Matrigel™, displaying some particulate/impurities. (
b
) The self-assembling
peptide RADA16-I nanofi ber scaffold lacking particulate appearance and having nanopores (aver-
age 5-200 nm). Such nanopores can allow slow diffusion of small molecular drugs (1-2 nm) and
proteins (2-10 nm). This is in sharp contrast to many other biopolymer microfi ber materials where
the micrometer pores permit drugs and proteins to diffuse rather quickly. Scale bars, 0.5 m m
4
Ideal Biological Materials
Although there are a number of criteria to fabricate biological scaffolds, the ideal
3-D biological scaffolds should meet several important criteria: (1) the building
blocks should be derived from biological sources; (2) basic units should be amena-
ble to design and modifi cation to achieve specifi c needs; (3) exhibit a controlled rate
of material biodegradation; (4) exhibit no cytotoxicity; (5) promote cell-substrate
interactions, (6) afford economically scalable and reproducible material production,
purifi cation and processing; (7) be readily transportable; (8) be chemically compat-
ible with aqueous solutions and physiological conditions; (9) elicit no or little
immune responses and infl ammation if used in human therapies; (10) integrate with
other materials and tissue in the body.
4.1
Self-Assembling Peptide as Biological Material
Construction Units
In the construction industry many other parts of house, such as doors and windows
can be prefabricated and then programmed assembled according to architectural
plans. If we “shrink” the construction units many orders of magnitude into nano-
scale, we can apply similar pre-fabrication principles to construct molecular materi-
als and devices, through molecular programmed molecular assembly, as well as
self-assembly. We limit our discussion below to three self-assembling construction
units: (1) “Lego peptide” that forms well-ordered nanofi ber scaffolds for 3-D cell
