Design and Synthesis of Photoreactive Polymers for Biomedical Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 265

thermoresponsive polymers were employed for investigation on cellu-
lar interactions [59-62]. One thermoresponsive copolymer, poly( N -iso-
propylacrylamide-co-acrylic acid), was coupled with azidoaniline. The
azidophenyl-derivatized copolymer was grafted in a specifi c pattern
onto a polystyrene matrix by photolithography. The surface micropattern
appeared and disappeared interchangeably, as observed under phase-
contrast microscopy, by varying the temperature between 10

° C and 37 ° C.

The copolymer-grafted polystyrene surface was hydrophobic at 37 ° C and

hydrophilic at 10 C. Albumin and fi bronectin adsorption on the matrix was

investigated using fl uorescence labeling. Fibronectin was adsorbed onto
both the grafted and nongrafted regions, while albumin was adsorbed more
onto the nongrafted regions than the grafted regions. Protein adsorption did
not affect surface wettability. Mouse fi broblast STO cells were cultured on
tissue culture plates pattern-grafted with this thermoresponsive copolymer.
Fibronectin adsorption enhanced cell spreading, whereas albumin reduced
it. When the temperature was lowered, the cells detached selectively from
the surface areas grafted with the thermoresponsive copolymer when cul-
tured in serum-free medium; the cells only partially detached from these
areas when cultured in serum-containing medium. The effects of serum pro-
teins on cell detachment were similar to that caused by a mixture of albu-
min and fi bronectin. Albumin adsorption did not affect the detachment of
cells, whereas fi bronectin adsorption inhibited it. These results indicate that
a pattern-grafted, thermoresponsive, azidophenyl-derivatized copolymer
can effectively facilitate selective cell detachment under conditions such
as serum-free culture or following the adsorption of albumin. The pattern-
grafting technique will be useful for qualitative microscopic comparison of
surfaces prepared differently on single chips under the same conditions.

°

11.3.3 Other Polymers

A protein microarray, called a “cell chip,” was constructed by using a pho-
toreactive poly(acrylic acid) for a cell adhesion assay [63]. Various amounts
of albumin or fi bronectin were immobilized covalently onto a polysty-
rene dish using a microspotter with a dip pen. Poly(acrylic acid) carrying
azidophenyl groups was synthesized as the photoreactive polymer. An
aqueous solution of this polymer (several nanoliters) was cast using the
dip pen of the microspotter and dried in air. Subsequently, aqueous solu-
tions of proteins were cast on the same place using the microspotter. After
drying, the dish was irradiated with UV light. Finally, the immobiliza-
tion was confi rmed by staining with a dye. The immobilization was stable
even after washing with Tween-20 detergent. The protein-immobilized
area depended on the manipulation of the microspotter and the size of
the dip pen. Subsequently, cell adhesion on the photoimmobilized protein
microarray was investigated. The adhesion behavior of cells depended on