Photoresponsive surfaces azobenzene

FIGURE 5.5.3 Control of cell adhesion on photoresponsive surfaces, (a) Access control of GRGDS peptides for biospecific cell adhesion by photoinduced cis-trans Isomerization of terminal azobenzene residues in grafted polymers (54). 

Novel Methodology for Immobilization of Biomolecules on the Surface of a Photoresponsible Polymer Containing Azobenzene Moiety... 

These photoresponsive peptides form stable monolayers at the air/water interface,the structure of which depends on the isomerization of the azobenzene. Photoisomerization, therefore, induces changes in the structure, and with that an increase in the areal requirements at constant surface pressure. As confirmed by UV-vis spectroscopy, LBK films of these peptide mono-layers deposited on quartz glass also retain the ability to isomerize. 

This chapter focuses on azobenzene-containing organosilanes that are precursors for preparing photoresponsive silica materials, mesoporous sihca materials with azobenzene moieties on the pore surfaces, and azobenzene-modified polysilsesquioxane gels. 

Brinker and coworkers also prepared photoresponsive nanoporous silica particles using aerosol-assisted assembly, EISA, and surfactant-directed self-assembly (SDSA) techniques (Liu, 2004). The as-prepared photoresponsive nanocomposite particles were prepared so that the azobenzene ligands pointed toward the hydrophobic micellar interiors. After surfactant removal by solvent extraction, nanoporous particles with azobenzene ligands positioned on the pore surfaces were formed (Fig. 13.8). 

Fig. 20 S ilicon wafer surface graphted with an azobenzene derivative, for photoresponsive molecular "imprinting->extracting->uptaking->shuffling" cycles, mediated by recognition of azobenzene by CD-template (theophylline, TPE) conjugates. Reproduced with permission from ref. 101. Copyright 2013 American Chemical Society.

Gold NPs with azobenzene terminated alkane thiol chains chemisorbed on the surface and complexed with a-CD gave a photoresponsive suspension in water, in which the azobenzene photosomerization was as efficient as that of the free molecule. Preferential complexation of the allgrl chain in both trans- and ds-azobenzene configurations favoured the water solubility of the alkyl-aromatic moiety and the chemisorption process and reduced the interaction between the azobenzene units on the particle surface with positive effects on the efficiency of the photoisomerization. 

Another typical photoresponsive material for preparation of switchable surfaces is the spiropyran-merocyanine system. The spiropyran isomerizes to zwitterionic merocyanine conformation by UV exposure, and the reverse reaction can be triggered by irradiation with visible light as well as azobenzene. The changes in hydrophilic/hydrophobic properties through the isomerization of spiropyran groups also enable the control of cell adhesion/ detachment. Edahiro et al. reported photoresponsive cell culture substrates grafted... 

---