Biomimetic Nanofi brous Scaffolds for Bone Tissue Engineering Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 73

Bioactive head

Hydrophilic segment

Hydrophobic tail

Figure 4.1 Schematic of peptide amphiphile molecule showing hydrophobic and
hydrophilic segments, and a biologically active head (i.e., binding site or growth
factor). The linear peptide amphiphiles self assemble into fi brillar micelle structures,
which in turn form thicker fi bers in a gel-like network. Adapted from Zhang et al. ,
2012 [117], Copyright © 2012 Elsevier Inc., permission obtained from Elsevier Inc.

suitable for bone ingrowth have been reported. The hydrogel nature of
the scaffolds renders PA-based materials extremely weak mechanically,
unable to support any physiological loading. More complicated scaf-
folds incorporating peptide amphiphiles together with collagen and
poly(glycolic-acid) fi bers to obtain better mechanical properties and
scaffold morphology have recently been developed, but the advantages
of incorporating PAs into a collagen-based material have not been fully
investigated [43]. Peptide-amphiphile-based self-assembly systems are by
far the most common, but other self-assembling materials such as self-
complementary collagen-like molecules [44], or peptides which form
b -sheet structures [45] have also been produced and may ultimately offer
improved control over scaffold morphology, but have only recently been
developed and their potential is largely unknown.

4.2.2 Biological Properties of PA Scaffolds

For bone tissue engineering applications, the ultimate utility of PA or
other self-assembled scaffolds is largely unknown. PA scaffolds with
a phosphorylated serine residue, which binds strongly to calcium ions,
have been shown to mineralize in a manner similar to natural collagen
fi bers [41], and MC3T3 murine pre-osteoblasts survive and proliferate
while embedded in PA scaffolds for up to 3 weeks with no signs of toxicity