ブックタイトル高分子　POLYMERS　62巻12月号

概要

高分子　POLYMERS　62巻12月号

Front-Line Polymer Science高分子科学最近の進歩elastomer within the CCAs template. 43）Hydrogels responsive to electrical current have beenof significant interest for their application in biosensingand for reflective displays. Walish et al. 44）havedesigned electrical current-responsive multilayer PhCswith a block copolymer. An electrochemical reactionchanges the chemical nature of the solvent in the blockcopolymer and thus causes a change in layer spacing.Yang et al. employed the mechanism of electrophoresisas a basis for the construction of electrical currentresponsivematerials. 45）They used highly chargedpolystyrene nanoparticles as the elements of non-closepackedPhCs.3.2.2 PhC hydrogels responsive to chemicalsLike hydrogels that can respond to physical stimuli,hydrogels with functional groups can swell or shrinkin response to chemical stimuli. When photonicnanostructures are constructed using these hydrogels,their PBGs can be shifted by using correspondingchemical stimuli. These materials show promise fornumerous applications as chemical sensors. Asher andco-workers 46）have pioneered the non-close-packed PhCfilm for pH detection. They embedded CCAs within acarboxylated hydrogel matrix to monitor their volumephasetransitions in response to pH. Lotsch et al. 47）reported a versatile PhC sensing motif, which wasa stimuli-responsive 2D PhC based on a monolayerinverse opal of polyelectrolyte hydrogel. The remarkablefeature of this particular PhC hydrogel was that itmaintained responsive properties despite a submicronthickness. Therefore, the PhC sensing did not sufferfrom slow diffusion of the target ions, and the responsewas greatly accelerated.To sense other kinds of ions, Asher et al. 48）attachedcrown ethers to the PhC hydrogel to bind Pb 2＋selectively. The binding of Pb 2＋to the crown ethersresulted in contraction of the hydrogel, which probablyreflected a decrease of the lattice spacing. Becausethe lattice spacing of the CCAs would vary accordingto the concentration of Pb 2＋, information regardingthese target ions in solution could be indicated by colorchanges of the PhC sensors.3.2.3 PhC hydrogels responsive to biochemicalsBiochemically responsive hydrogels could mimicthe recognition behavior of biological systems andthus identify specific molecules to produce a stimulusresponse. Because of their unique properties, such asreversible swelling behavior, permeability, mechanicalproperties and high sensitivity to external stimuli,hydrogels show promise for applications as biosensors.Given the importance of biochemically responsivehydrogels, we will introduce their specific classificationaccording to their responsive target and currentresearch progress.3.2.3.1 GlucoseGlucose-responsive hydrogels can recognize glucosemolecules to produce a stimulus response（see I I）.The response mechanisms for glucose-responsivehydrogels are mainly based on glucose oxidase,concanavalin A（Con A）and phenylboronic acid（PBA）（Fig.3 a, b, c）. Glucose detection shouldenable a successful initial biomedical application of theresponsive PhC sensors because it may be an effectivetool for the diagnosis of diabetes. Glucose-sensitive PhCshave been fabricated using the hydrogels with variousresponse mechanisms. For example, the Asher group 51）has fixed a biological molecular recognition unit in acolloidal crystal hydrogel for biological analysis. Usingthe principle that active epoxy functional groups ona hydrogel could be connected to glucose oxidase,glucose-sensitive PhCs were fabricated and used todetect the concentration of glucose. 50）,52）With theintroduction of functional groups such as boric acid,detecting glucose in an environment of high ionicstrength could also be achieved. Interestingly, Asher etal. have incorporated glucose-sensitive PhC hydrogelsinto a contact lens to achieve a noninvasive in vivoglucose test. Asher’s group has created a poroushydrogel PhC film using a PBA derivative immobilizedhydrogel as the essential material. When used in aglucose assay, the film swelled and thus changed itscolor, similar to the glucose sensor composed of nonclose-packedcolloidal crystal PhCs mentioned above.＊は、e！高分子のSupporting Informationにハイパーリンクされています。746c2013 The Society of Polymer Science, Japan高分子62巻12月号（2013年）Fig.3Glucose-responsive hydrogel based on（a）glucose oxidase,（b）Con A and（c）boronic acids.（d）Glucose contactlens sensor based on a colloidal crystal hydrogel. 49）,50）