Biomedical Engineering Reference
In-Depth Information
vice versa, the peptides did not self-assemble. When the alanines were replaced by hydrophobic resi-
dues, there was a greater tendency to self-assemble and form peptide matrices with enhanced strength.
This behavior of the peptide molecules has led the researchers to concentrate their attention
toward understanding the basis of protein conformational diseases. Protein conformational diseases
are a group of disorders characterized by accumulation of malformed protein structures in cells.
Proteins must fold into a proper three-dimensional structure to perform their normal physiological
functions. But when they do not fold properly, they form malfolded protein structures that accumulate
in cells leading to pathological conditions. Alzheimer's disease, Prion disease, and Parkinson's dis-
ease are a few examples of protein conformational diseases. Thus by understanding the mechanism of
formation of peptide nanofibers and the factors controlling their self-assembly, future research work
can be aimed in formulating remedies for protein conformational diseases. Earlier researches done
on three-dimensional peptide matrix scaffolds were not only limited to natural amphiphilic peptides
and synthetic complex amphiphilic peptides were also produced by joining twelve hydrophilic pep-
tides into long alkyl chains by pH control, divalent ion induction, and change in concentration
[36]
.
The peptide end of the molecule was designed to regulate biomineralization. Bone is produced as
a result of deposition of calcium and phosphate ions to form hydroxyapatite crystals. This process
is known as mineralization. Serine is a nonessential amino acid. When a phosphorylated serine was
incorporated with the synthetic amphiphilic peptide complex, it served to attract and organize cal-
cium and phosphate ions to form hydroxyapatite crystals
[37]
. The researchers further functionalized
the synthetic amphiphilic peptide complex by adding a cell-adhesion motif
[37]
. It was the arginine-
glycine-aspartic acid (RGD) complex that was attached to the C-terminus of the peptide. This can
be used to study the ability of the bone cells to differentiate, proliferate, and adhere to a biomaterial
surface like titanium. Titanium alloys offer several benefits, including lower elastic modulus, excel-
lent corrosion resistance, and enhanced biocompatibility
[39]
. Due to these characteristics, titanium
is the most widely used biomaterial surface to produce orthopedic implants, dental implants, and hip
(A)
(B)
Inner
helix
Outer
helix
FIGURE 13.11
(A) The inner and outer
β
-helices of KFE8 peptide form a double-sheet helix with hydrophobic
side chains sandwiched between the two layers. (B) Atomic force microscopy (AFM) image
(500 nm 500 nm) of peptide solution deposited over mica.
