Biomedical Engineering Reference
In-Depth Information
Fig. 4
Design of various peptide materials. (
Top Panel
) Peptide Lego, also called ionic self-
complementary peptide has 16 amino acids, ~5 nm in size, with an alternating polar and nonpolar
pattern. They form stable b-strand and b-sheet structures, thus the side chains partition into two
sides, one polar and the other nonpolar. They undergo self-assembly to form nanofi bers with the
nonpolar residues inside (
green
) and positively (
blue
) and negatively (
red
) charged residues form
complementary ionic interactions, like a checkerboard. These nanofi bers form interwoven matri-
ces that further form a scaffold hydrogel with very high water content, >99.5% water. (
Middle
Panel
) Peptide surfactant, ~2 nm in size, which has a distinct head group, either positively or nega-
tively charged, and a hydrophobic tail consisting of six hydrophobic amino acids. They can self-
assemble into nanotube and nanovesicles with a diameter of ~30-50 nm (image courtesy Steve
Yang and Sylvain Vauthey). These nanotubes go on to form an interconnected network. (
Bottom
Panel
) Peptide ink. This type of peptide has three distinct segments: a functional segment where it
interacts with other proteins and cells; a linker segment can be fl exible or stiff, and it sets the dis-
tance from the surface; and an anchor for covalent attachment to the surface. These peptides can
be used as ink for an inkjet printer to directly print on a surface, instantly creating any arbitrary
pattern, as shown here. Neural cells from rat hippocampal tissue grown on peptide ink substrate
with defi ned pattern. (Images courtesy Sawyer Fuller)
culture and for regenerative medicine; (2) “lipid-like peptides” for drug, protein
and gene deliveries as well as for solubilizing and stabilizing membrane proteins;
(3) “peptide ink” for surface biological engineering (Fig.
4
). These designed
construction peptide units are structurally simple and versatile for a wide spectrum
of applications as nanobiomaterials and beyond.
4.1.1
Discovery of Self-Assembling Peptide Scaffolds
The self-assembling peptide scaffold belongs to a class of biologically inspired
materials. The fi rst member, EAK16-II (AEAEAKAKAEAEAKAK), of the family
was discovered from a segment in a yeast protein, Zuotin (Zhang et al.
1993
) ,
that was characterized as a left-handed Z-DNA binding protein (Zhang et al.
1992
).
