Chapter 7: Target Molecule-responsive Hydrogels

Stimuli-responsive hydrogels undergo changes in volume in response to environmental changes such as pH, temperature and so on. Although a variety of stimuli-responsive hydrogels have been designed for their applications as sensors, drug delivery systems and cell culture, there have not been so many studies on target-molecule-responsive hydrogels that sense a specific molecule and undergo structural changes according to its concentration because of difficulties in combining molecular recognition events with responsive changes in the structure within hydrogel networks. This chapter provides an overview of important and traditional studies on target molecule-responsive hydrogels designed using various strategies for the combination of molecular recognition and responsive changes of the network structure. Not only strategical design and applications of target molecule-responsive hydrogels but also micro- and nano-sized hydrogels such as particles, layers and microdevices are introduced. The fascinating properties of the target molecule-responsive hydrogels suggest that they have many future opportunities as smart materials for biomedical and environmental applications.