Design and Synthesis of Photoreactive Polymers for Biomedical Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 267

with an increased viability of encapsulated hMSCs and a more tightly
crosslinked network in one-third the time taken for UV polymerization
with 2-hydroxy-4 -(2-hydroxyethoxy)-2-methylpropiophenone. Younes

et al. [69] reported a new family of photocrosslinked amorphous poly
(diol-tricarballylate) biodegradable elastomeric polyesters. Liquid-to-solid
photocuring was carried out by exposing the polymer to visible light in
the presence of camphorquinone as a photoinitiator. These new elasto-
mers can be considered as candidates for use in controlled implantable
delivery systems of protein drugs and in other biomedical applications.
Cui et al. [70] reported on the facile preparation of chemically crosslinked
alginate microgels in mild conditions by using a reversed microemulsion
technique. Sodium alginate was modifi ed by partially grafting phenol
groups to the backbone, on the basis of which microgels have been pre-
pared by the irradiation of visible light in the presence of catalyst Ru(II)
complex at room temperature. Visible light-induced dextran-methacrylate
hydrogels were also prepared using a different photoinitiator and coinitia-
tor to enlarge the applications of this material in the biomedical area (e.g.,
for eyes or other light-sensitive organs) [71, 72]. Moreover, crosslinking of
DNA protein in solution by visible light in the presence of several sensitiz-
ers such as methylene blue has also been investigated [73, 74]. Recently, a
new biocompatible strategy for photoinduced DNA interstrand crosslink-
ing was reported. Methylene blue-induced 1 O 2 formation triggers furan
oxidation, and the resulting aldehyde then rapidly reacts with comple-
mentary adenine or cytosine with formation of stable adducts [75].
We have developed a new visible light-curable polymer system com-
prising a furan-incorporated biopolymer such as gelatin [76] or chitosan
[77, 78] and the dye Rose Bengal with absorbance at a visible light wave-
length. When the system is irradiated with visible light, the activated Rose
Bengal oxidizes furan groups and the peroxidized furan is decomposed,
forming a radical group that crosslinks biopolymers with each other, as
shown in Figure 11.14. The reaction occurs in water. Considering that

′

O

O O O

1 O 2

RB*

Hydrogels

Visible light

RB O 2

O

Biopolymer

Figure 11.14 Visible light used in crosslinking biopolymer systems. RB indicates
Rose Bengal.