Self-Assembly of Proteins and Peptides and Their Applications in Bionanotechnology and Dentistry - Emerging Nanotechnologies in Dentistry - page 214

replacements [40-42] . In spite of its excellent biocompatibility, titanium implants still fail [43,44] .
Most orthopedic implants have a lifetime of 15 years to the maximum [45] . In order to fabricate
titanium implants with lesser failure rate, its surface has to be modified with nanosized surface pat-
terns so that bone cells (osteoblasts) can attach, differentiate, and migrate into these patterns result-
ing in enhanced bone-implant adhesion. For such a purpose, poly(ethylene glycol) (PEG) hydrogel
micropatterns with osteoinductive growth factors have been reported [46] . These osteoinductive PEG
micropatterns were shown to stimulate rat osteoblast migration. Self-assembling synthetic amphiphi-
les and peptide hydrogels can be fabricated on titanium surfaces to regulate and control the osteo-
blasts [47] . These protein and peptide sequences can be efficiently functionalized with osteoinductive
growth factors and cell-adhesion motifs like the RGD peptide sequence [47] .
13.8 ADVANTAGES AND LIMITATIONS OF SELF-ASSEMBLING PEPTIDE
MATRIX SCAFFOLDS
As understood from the earlier studies, macroscopic three-dimensional peptide matrices can be engi-
neered from various self-assembling peptides. The advantages of using designer peptides for the fab-
rication of three-dimensional matrices for tissue engineering include (1) easy design using known
biologically active peptide sequences, (2) these scaffolds provide the opportunity to incorporate a
number of different functional motifs and their combinations to study cell behavior in a well-defined
ECM-analogue microenvironment, not only without any chemical cross-link reactions but also with
fully bio-resorbable scaffolds, (3) biodegradable by a variety of proteases in the body with superior
biocompatibility with the tissues, (4) designer peptides can be readily modified at the single amino
acid level at will, inexpensively and quickly using conventional, commercially chemical peptide
synthesis methods, and (5) these designer peptide scaffolds are pure with known motifs and can be
used to study controlled gene expression or cell signaling processes [48,49] . Thus these new designer
nanofiber scaffolds have proven to be promising tools for bionanotechnological applications. In
enthusing about the many good properties of self-assembling proteins and peptides, it is important not
to lose sight of the limitations. If a material is copied from nature, then one cannot assume that the
material will perform well in environments or applications that are very different from those found
in nature. Self-assembly of proteins and peptides have unique capabilities as a chemical processing
method and the biologic characteristics. Thus far it has penetrated little from the laboratory to manu-
facturing and practical applications. The limitations on its employment of these self-assembled matrix
scaffolds appear to be practical rather than fundamental [50,51] .
13.9 SELF-ASSEMBLY IN REGENERATIVE BIOLOGY AND DENTISTRY
As self-assembled peptide matrix scaffolds encouraged cell proliferation and differentiation and were
also able to support various types of cell attachments [52,53] , the ability of the peptides to support
attachment of mouse neuronal cells was evaluated using self-assembling ionic self-complementary
β-sheet oligopeptides [52] . The primary mouse neuron cells formed active connections with the
peptide scaffolds. These three-dimensional scaffolds are being tested for their applications in neu-
ron regeneration and treatment of related neuropathology [54,55] . In regenerative medicine, these
peptide matrices can be used to cultivate chondrocyte ECM which can further be used to repair