PEPTIDE SELF-ASSEMBLY BIOMATERIALS DESIGN AND APPLICATION - Biologically-Responsive Hybrid Biomaterials - page 74

scaffolds for 3D cell culture and for regenerative medicine; peptide surfactants or
detergents for drug, protein and gene deliveries as well as for solubilizing and
stabilizing membrane proteins; and “peptide ink” for surface biological
engineering. These designed construction peptide motifs are structurally simple
and versatile for a wide spectrum of applications.
Peptide lego
Molecular-designed peptide Lego, at the nanometer scale, resembles the Lego
bricks that have both pegs and holes in a precisely determined organization that
can be programmed to assemble in well-formed structures. This class of peptide
Lego can spontaneously assemble into well-formed nanostructures at the
molecular level. The first member of the peptide Lego was serendipitously
discovered from a segment in a left-handed Z-DNA binding protein in yeast and
named Zuotin (Zuo means left in Chinese, tin means protein in biology) [1, 2] .
This class of designer self-assembling peptides forms Ȳ -sheet structures in
water and in aqueous solution, thus forming two distinct surfaces: one
hydrophilic and the other hydrophobic, like the pegs and holes in Lego bricks. In
aqueous solution, the hydrophobic sides shield themselves from water, thus
facilitating the peptide to undergo intermolecular self-assembly, similar to what
is seen in the case of intramolecular protein folding. The unique structural feature
of these ''peptide Lego'' systems is that they form complementary ionic bonds
with regular repeats on the hydrophilic surface (Figure 2). The complementary
ionic sides have been classified into several modules, i.e. modules I, II, III, IV,
RADA16-1
RADA16-2
EAK16-1
EAK16-2
From Zoutin
Fig. 2. Molecular models of several self-assembling peptides, RAD16-I, RAD16-II, EAK16-I and
EAK16-II. Each molecule is Ä 5 nm in length with 8 alanines on one side and 4 negative and 4
positive charged amino acids in an alternating arrangement on the other side. AFM image of
RADA16-I nanofiber scaffold (PuraMatrix). Note the nanofiber scale fiber with pores ranging from
5-200 nm, the correct pore size for biomolecular diffusion. This is in contrast to the microfibers of
traditional polymer scaffolds, in which the fiber diameter is Ä 10-50 micron and the pores range
from 10~200 microns.