Design and Synthesis of Photoreactive Polymers for Biomedical Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 254

gelatin. In addition to these proteins, basic fi broblast growth factor
(bFGF)—used for inducing cell proliferation and secretion of angiogenic
factors—together with proteoglycan heparan sulfate was immobilized by
Doi et al. [25, 26]. They prepared microporous gelatin-treated small-caliber
segmented polyurethane grafts for tissue regeneration at both perianasto-
motic and transmural sites in rat arteries. Impregnated grafts were coated
with a mixture of photoreactive gelatin (gelatin with photoreactive benzo-
phenone groups), bFGF, and heparin and photocured with UV irradiation
to obtain the coimmobilization of bFGF and heparin. Nonimpregnated
control grafts were coated with photoreactive gelatin alone. Both graft
types (impregnated and nonimpregnated) were implanted in rat aortas for
4 weeks. Endothelialization in the bFGF/heparin coimmobilized (impreg-
nated) grafts was found to be greater in extent than in the control grafts.
Coimmobilization of bFGF/heparin using photoreactive gelatin enhanced
neoarterial generation through perianastomotic and transmural tissue
ingrowth [25]. Doi et al. [26] also prepared polyurethane grafts with con-
trolled micropore diameter and distribution attained using a computer-
aided excimer laser ablation technique. The prepared grafts were coated
with photoreactive gelatin and fi xed photochemically to the polyurethane
surfaces using UV. Upon UV irradiation, the photoreactive gelatin bound
covalently to the surface and acted like an artifi cial extracellular matrix.
This can help in endothelialization and can be used to immobilize bio-
logical molecules that can facilitate tissue growth, such as growth factors.
These coatings also increase the biocompatibility of grafts. Thus, a com-
bined excimer laser approach using microporation and photochemical
gelatin processing onto surfaces is helpful for enabling transmural tissue
growth [26].
On the other hand, Chung et al. [27] modifi ed gelatin with 1-(2-carboxy-
ethyl)thymine using carbodiimide as a coupling agent as shown in Figure
11.7a. Upon UV irradiation, photoreactive thyminated gelatin underwent
crosslinking. The crosslinking is directly proportional to the degree of
derivatization using thymine and UV irradiation time. They also proved
that the photoreactive thyminated gelatin can be used for sealant or hemo-
static applications in laparoscopy [27].
Nakayama et al. [28] developed a photocurable glue with a combi-
nation of photoreactive gelatin and poly(ethylene glycol) diacrylate
(PEGDA). UV-photocurable agents such as benzophenone and visible
light-photocurable agents such as fl uorescein, eosin, and Rose Bengal were
coupled with gelatin to make photoreactive gelatin. PEGDA molecules of
various molecular weights (1,000, 2,100, and 3,900) were used along with
photoreactive gelatin at different concentrations to prepare hydrophilic
gels with high adhesiveness. This property arose from photocrosslinking
and photograft polymerization. These photocurable glues can be used for
tissue adhesion in cardiovascular and endoscopic surgery because of their