ARTIFICIAL BINDING GROWTH FACTORS - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 342

(R136K-CBD).R136KisanengineeredbFGFthathasthrombinresis-
tance.Theseauthorsusedsurfaceplasmonresonance(SPR)analysis
to show that the binding a nity of the fusion protein was fourfold
higher than that of native bFGF and R136K. R136K-CBD stimulated
endothelialcellangiogenesisinfibringel.However,theadvantageof
thecollagen-bindinga nityofthefusionproteinduringangiogene-
sis was not clearly shown viacomparison with unfused R136K.
A short polypeptide sequence of the human collagenase CBD
was also employed to construct collagen-binding fusion proteins
of platelet-derived growth factor BB (PDGF-BB), 20 bFGF, 21 BMP2, 22
and nerve growth factor (NGF). 23 Zhao et al . 21 compared a short
polypeptide sequenceofvWFwiththat ofhuman collagenaseasthe
fusion partner for bFGF and found that the latter provides a higher
binding a nity to collagen. Considering that the same growth fac-
tors fused with different partner polypeptides were synthesized (as
shown in Table 17.1), the comparison of the properties of these fac-
tors, as reported by Zhao et al ., 21 isimportant.
Fusion proteins of the CBD of fibronectin and EGF, 24 VEGF, 25 or
HGF 26 were also produced. This fusion design (Fig. 17.2) was also
applied to BMP4 (Kitajima et al ., unpublished). These fusion pro-
teins exhibit binding a nity to major collagen types (I-V), which is
not observed for the native growth factors. Moreover, they showed
native biological activities in the collagen-bound state. These fusion
proteins can be stored for longer periods than native growth fac-
tors. For example, collagen-binding EGF (FNCBD-EGF) bound to
collagen-coated plates or diluted in culture medium showed no loss
of EGF activity after one month of storage at 4 ◦ C, while native EGF
lost its activity in the same conditions (Fig. 17.3). The stability of
collagen-binding HGF (CBD-HGF) in culture medium at 37 ◦ Cwas
also confirmed 26 : CBD-HGF continued to stimulate the proliferation
of endothelial cells without supplementation, both in the soluble
and in the collagen-bound state, for longer periods than native HGF.
The fused CBD moiety may protect the growth factor moieties from
degradation ordenaturation.
When injected into muscle tissues, FNCBD-EGF bound to colla-
gen distributes along muscle fibers, while EGF is not retained in the
tissues. 27 It was also shown that FNCBD-EGF binds to type IV col-
lagen (basement membrane) exposed on the inner surface of blood