Enzyme-triggered polymers

Enzyme-triggered release of bioactive molecules from a polymer based material is possibly the most intensely researched application for enzyme-responsive polymers. Such delivery systems typically employ vehicles such as micelles, solid particles and capsules to contain and protect a drug and deliver it to the site of action either by injection directly into the diseased tissue or by circulation through the blood stream. At the site of action, the enzyme will degrade the polymer, cause disassembly of the micelle or swell the particle and thus cause release of the drug into the environment. 

The major advantage of enzyme responsive polymers is that they do not require an external trigger. For instance, polymer systems based on alginate/chitosan or DEXS/chitosan microcapsules are responsive to chitosanase [126]. On the other hand, azo-aromatic bonds are sensitive to azo-reductase [127]. These enzymes, naturally produced by bacteria principally located in the colon, are capable of degrading polysaccharides like pectin, chitosan, amylase/amylopectin, cyclodex-trin and dextrin [120,125, 165]. 

The design and development of enzyme-responsive polymers emerged recently as a promising new research area in stimuli-responsive materials and rely on polymers that suffer macroscopic property changes when triggered by the biocatalytic action of an enzyme (de la Rica et al., 2012). 

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