Design and Synthesis of Photoreactive Polymers for Biomedical Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 266

the kind of immobilized proteins and the kind of cells. Such protein micro-
arrays will be useful for cell diagnosis and for selecting biomaterials to
regulate cell behavior.
Photoreactive polyallylamine containing b -galactose moieties in the side
chain (LPAN3) was prepared by the reaction of polyallylamine with lacto-
bionic acid and azidobenzoic acid [64]. To create micropatterned surfaces,
a LPAN3-coated poly(methyl methacrylate) (PMMA) substrate was irradi-
ated with a UV lamp under a photomask. The presence of a LPAN3 layer on
the substrate was confi rmed using ESCA. Micropatterned cell culture was
carried out by seeding hepatocytes and/or fi broblasts on the substrate. They
adhered only to the LPAN3 and PMMA lanes, respectively. Co-culture on
the stripe-patterned substrate was carried out by fi rst seeding hepatocytes
and then by seeding fi broblasts. The co-cultured cells produced extracellular
matrix molecules such as fi bronectin, indicating normal biological activity.
Poly(acrylic acid), polyallylamine, gelatin, and poly(2-methacryloy-
loxyethyl phosphorylcholine-co-methacrylic acid) (PMAc50) coupling
with azidophenyl groups were photoimmobilized on conventional poly-
styrene cell culture dishes [65]. Mouse ES cells were cultured on the
immobilized polymer surfaces. Cell morphology, cell growth, staining
for alkaline phosphatase, activation of the transcription factor stat3, and
expression levels of the octamer-binding protein 3/4 transcription factor
and the zinc fi nger-containing transcription factor were observed. ES cell
morphology and growth rate were signifi cantly affected by the polymer
surface properties. The ES cells attached to both gelatin and polyallyl-
amine surfaces; however, colonies formed on the former but not the latter.
In addition, signifi cant enhancement of ES cell growth was observed on
the gelatin surface. In contrast, ES cells aggregated to form embryoid bod-
ies on the photoimmobilized poly(acrylic acid) surface and the PMAc50
surface, although the cell growth rate was reduced. Signifi cant enhance-
ment of aggregation of ES cells onto the PMAc50 surface was observed in
terms of morphology and gene expression analyses. Chondrogenic or adi-
pogenetic differentiation of mesenchymal stem cells was also investigated
on the micropatterned polyelectrolyte surfaces [66, 67].

11.4 Visible Light-Reactive Biopolymer Systems

Irradiation using visible light instead of UV light could bring many advan-
tages for biomedical applications. Visible light irradiation has been used
to crosslink some synthetic or natural polymers for biomedical purposes.
For instance, Johnstone et al. [68] defi ned nontoxic conditions for photoen-
capsulating human mesenchymal stem cells (hMSCs) in PEGDA scaffolds
using a visible light photoinitiator system composed of eosin Y, trietha-
nolamine, and 1-vinyl-2-pyrrolidinone. This produced hydrogel scaffolds