Depending on the Azobenzene Moiety

This section compares the photoindueed immobilization of IgG on two types of azopolymers (shown in Fig. 9.2) bearing various concentrations of 4-amino-4 -cyanoazobenzene (CN-azopolymer) or amino azobenzene (H-azopolymer). CN-azopolymer and H-azopolymer eontain a push-pull-type azobenzene and an amino azobenzene, respectively (Rabek, 1988). These azobenzenes have different 

The photodeformation capabilities of the CN-azopolymer and the H-azopo-lymer were examined by determining the depth of the indents formed by polystyrene microspheres under LED irradiation. After photoirradiation and removal of the microspheres, regularly arranged indented patterns formed by the microspheres were observed on the surfaces of the azopolymers. The depths of the indents were plotted as a function of irradiation time for several kinds of azopolymers, as shown in Fig. 9.14. The indent depths in the azopolymer increased with increasing irradiation time. The depths of the indents saturated and reached a maximum after 30 min of photoirradiation for each of the azopolymers. The saturated depths were lowest in those azopolymers with the lowest content of azobenzene moieties. These results indicate that the photo-responsive moiety plays an important role in inducing photodeformation and that the indent depth is related to the content of the azobenzene in the azopolymers. There were no differences in photodeformation capabilities between the CN- and 

H-azopolymers, even though they contained different types of azobenzene. These results show that H-azopolymers could exhibit immobilization capabilities similar to CN-azopolymers, despite the differences in their chemical structures. 

Photoimmobilization of IgGs was achieved by performing photoirradiation for 30 min to examine the efficiency of the immobilization process. The relative efficiencies of the photoimmobilization processes on the different azopolymers were plotted as a function of their azobenzene contents, as shown in Fig. 9.15. The immobilization efficiencies of both the CN- and H-azopolymers. increased with azobenzene content up to 30 wt% and then became saturated, although the saturated values were different between the CN- and H-azopolymers. This result indicates that an azobenzene moiety that exhibits photoisomerization is essential to immobilize IgGs on azopolymers when using a photoimmobilization process. 

the authors confirmed the relationship between the immobilization of IgG and the deformation efficiency of the azopolymer. The relative immobilization efficiencies were plotted as a function of indent depth, as shown in Fig. 9.16. Incremental changes in the immobilization efficiency were observed by increasing the depth of the indents. However, the immobilization efficiency of the H-azopolymers was higher than that of the CN-azopolymers across the whole range, and this is also shown in Fig. 9.15. This difference shows that the degree of photoimmobilization is not only affected by the deformation capability but is also a property of the surface of the azopolymer and is related to the chemical structure of the azobenzene that is incorporated in the azopolymer. Whitesides and coworkers have also reported that immobilization is influenced by the properties of the surface (Ostuni et al., 2001). 

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