Design and Synthesis of Photoreactive Polymers for Biomedical Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 252

groups coupled with either proteins or polymer and the azidophenyl group
during photolysis produce phenyl nitrene groups, which are responsible
for the covalent bond formation that leads to photoimmobilization. They
prepared N -((4-azidobenzoyl)oxy)succimide-coupled proteins (albu-
min and gelatin) as shown in Figure 11.4a and synthetic polymers (poly
(3-azidostyrene) and poly( N,N -dimethylacrylamide-co-3-azidostyrene)).
Synthesized azidophenyl-coupled proteins were immobilized onto the
unmodifi ed polymers. Microchemical immobilization using UV light was
characterized by electron spectroscopy for chemical analysis (ESCA), col-
orimetric immunostaining using antibodies, and atomic force microscopy
(AFM). These measurements demonstrated that photoimmobilization is
simple for making micropatterns [1].
Similarly, we have synthesized UV-reactive gelatin for covalent photo-
immobilization of biological molecules in several ways to induce specifi c
biological responses on material surfaces [3-10]. Photoimmobilization
is an effective method for this as it introduces photoreactive groups to
the molecules independently of the surface functional groups. For exam-
ple, the placement of covalently immobilized growth factor proteins by
photoirradiation signifi cantly enhanced cell growth when used for cul-
ture in vitro . Micropattern immobilization of growth factors achieved by
photocrosslinking was very effective to confi rm this effect because
cell growth was observed only on the treated regions. The method for
micropatterning using photolithography is illustrated in Figure 11.5a.
Recently, the origin of photoreactive gelatin has been extended from
bovine to recombinant human tissues, and its potential for the surface
modifi cation of synthetic polymers has been examined using cell culture
and tissue engineering [11]. The micropatterning is shown in Figure 11.6.
Its effectiveness as a culture substratum was examined by culturing

N 3

N 3

+

( a ) Gelatin-NH 2

O

CO O

Gelatin - HN - CO

N

O

N 3

N 3

EDC/NHS

+

( b )

Gelatin — COOH

NH 2 Gelatin — CONH

Figure 11.4 Synthesis of azidophenyl gelatin derivatives. EDC/NHS indicates
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/ N -hydroxysuccimide.