Hydrogels in biosensing applications

This chapter gives an overview of the use of hydrogels in biosensing. Many intrinsic properties of hydrogels predetermine their use in this field of application. The most important points are their high water content that renders them biocompatible and allows diffusion of water-soluble compound through the polymer network as well as their chemical diversity and the ability to tune their properties both regarding the chemical nature of the polymer backbone and the introduction of (functional) side groups. This allows the generation and design of stimuli-sensitive hydrogels that may act as sensors themselves, for example, by introduction of hydrophobic groups for temperature sensitivity or protic groups for pH sensitivity. It also enables functionalization of the hydrogel with moieties that act as sensors. The range of molecules that can be and has been used for this purpose is very broad and comprises (fluorescence) dyes, luminescent compounds, enzymes, biochemical recognition sites such as oligonucleotides, antibodies, lectins, and very specific recognition mechanisms.