ARTIFICIAL BINDING GROWTH FACTORS - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 341

binding, without harmful treatment. In addition, it is possible to
achieve uniformorientation of molecules on thetargets.

17.3.1 Collagen-Binding Growth Factors
Collagen is the major component of the ECM and is present in
most tissues. It has been used as a material for scaffold preparation
because of its biocompatibility. To date, four kinds of polypeptide
sequencesfromtheCBDofdifferentproteinshavebeenemployedto
generate the collagen-binding growth factor: von Willebrand Factor
(vWF, 10 amino acids), bacterial collagenase ( ∼ 24 kDa), human col-
lagenase (eightamino acids), and fibronectin ( ∼ 40kDaor27kDa).
Nimni et al. produced a fusion protein of CBD with vWF
and TGF β 1 13 , 14 or other growth factors. Collagen-binding TGF β 1
(rhTGF β 1-F2) had a lower biological activity compared with its
native counterpart, both in the soluble state and in the collagen-
bound state. 13 Yet, when combined with a collagen gel, rhTGF 1-

F2 stimulated the migration and proliferation of mesenchymal stem
cells in the gel, as well as their differentiation to cartilage cells. 14
The osteogenic activity of this fusion protein was lower than that
ofnativeBMP2,withouta nitytocollagen.Otherfusionproteinsof
EGF(EGF-CBD), 15 basic(b)FGF(rhbFGF-F2), 16 andBMP3(rhBMP3-
C) 17 allshowedbindinga nitytocollagenandanactivitysimilarto
thatoftheoriginalmolecule:growthstimulatoryactivityonNIH3T3
cells(forEGF)andendothelialcells(forbFGF)andgrowthinhibitory
activity on bone cells (for BMP3). It was not clearly demonstrated
that these biological activities were exerted when they were com-
binedwithcollagen.
Nishi et al . 18 produced other fusion proteins using the collagen-
binding motif from bacterial collagenase fused to EGF or bFGF. Both
wereretainedfor5-10dayswhensubcutaneouslyinjectedintorats
(5-7 days), which suggests their tight binding to collagen or other
ECM components. The EGF fusion protein exhibited only 1/10 of
the original EGF activity, while the bFGF fusion protein showed an
activity comparable with that of the native molecule. The CBD used
may affect the activity of the fusion protein or its binding to the
receptor, depending on the growth factors being fused. Brewster
et al . 19 employed the same CBD to generate collagen-binding bFGF

β