Biomedical Engineering Reference
In-Depth Information
with
E. coli
and propagated. Their DNA and peptide sequences are then determined.
The concept of cell surface display is essentially the same. Cells bound to the
target compound are collected and propagated, and genes encoding the peptides
with binding activity are obtained.
Although display technology is commonly used in the molecular biological
field for identifying the interaction of biomacromolecules such as proteins and/or
peptides, it has also been used to recover peptides that bind to gold. Brown, for
example, used cell surface display to recover peptides that bind to gold and showed
that such peptides can be used to control gold crystal formation [
81
,
82
]. Since
then, display technology has been applied to research in the field of material science
and used to synthesize semiconductor crystals [
80
,
83
-
85
]. Mao et al. successfully
fabricate zinc blende and Wurtzite ZnS crystal systems using two kinds of artificial
peptides. The zinc blends structure was obtained in the presence of a peptide, and
the Wurtzite ZnS structure was obtained in the presence of another peptide.
Peptides that bind to HAP have been isolated using phage display. Gungormus
et al. used it for crystallization experiments in which two artificial peptides, a HAP
strong-binding peptide (HABP1, CMLPHHGAC) and a HAP weak-binding peptide
(HABP2, CNPGFAQAC), were added to supersaturated solutions with respect to
HAP and OCP. Only OCP was obtained in the presence of both peptides. Both
peptides delayed OCP formation, with more drastic effects seen in the presence of
HABP1. The OCP crystals obtained in the presence of HABP1 were significantly
larger than those obtained in the presence of HABP2 [
86
].
Roy et al. used phage display to isolate a peptide that binds to HAP [
87
]. The
peptide contained the amino acid sequence SVSVGMKPSPRP. It bound efficiently
to HAP, but did not bind to ACP or calcium carbonate, indicating that the peptide
recognize HAP-specific atomic sequences, and not calcium or phosphate ion ones.
Roy et al. showed that the peptide modified with fluorescent dye can be used for
imaging teeth. The use of this technology should make it possible to analyze the
processes of bone and teeth development with high sensitivity in vivo.
A peptide that can bind to titanium, commonly used for artificial bone, was
isolated using phage display [
88
]. Although titanium has good biocompatibility,
it does not bind to bone directly. Therefore, patients receiving a titanium implant
are generally obliged to restrict mastication for several weeks until tight adhesion
between the implant and surrounding bone is established. To overcome this
problem, methods to accelerate the adhesion process have been investigated. Bone
is synthesized by osteoblasts, and bone morphological protein 2 (BMP2) induces
differentiation of premyoblastic cells into the osteoblastic state. Therefore, it may be
possible that BMP2 immobilized on a titanium substrate induces cell differentiation
into osteoblastic state, which promotes tight adhesion between the titanium substrate
and surrounding bone. However, when BMP2 is directly attached to a titanium
surface, it becomes inactivate due to inappropriate interaction between the protein
and titanium surface. To overcome this problem, an artificial protein that binds
tightly to titanium was constructed using the titanium binding peptide as a building
block. The artificial protein was fused to BMP2, and the BMP2 was attached to a
