Enzyme responsive polymers mechanical

Enzyme-responsive polymers can be classified in various ways, for example according to their structure, function or response type or mechanism. Here, we classify enzyme-responsive polymers, according to their structural elements, into polymer hydrogels, supramolecular polymers, polymer particles and self-immolative polymers. The general properties of these classes and their importance in biomaterial apphcations will be introduced. Using examples from the recent literature, we will demonstrate how enzyme responsiveness can be incorporated into these materials. 

It is interesting that the enzymes responsible for the synthesis of the main extracellular polysaccharides (i.e. hyaluronan and cellulose) are localized in the cytoplasmic ceU membrane. During the synthesis, a growing polymer chain diffuses through the manbrane directly into extracellular space. Such a synthesis route is apparently more ancient and differs from the synthesis of other extracellular polysaccharides that are synthesized inside the cell and transported into extracellular media by the exocytosis mechanism. 

Characterisation of the enzyme-responsive material prepared through the methods outlined above is essential not only to test the enzyme responsiveness of the polymer but also to characterise the material s overall performance under the conditions in which it will be used in its ultimate application. This section will provide a brief overview of standard and specialised techniques that have been employed for this purpose and covers mechanical, chemical, physical and biological properties as well as enzyme responsiveness. While we will discuss the reason for choosing particular techniques and explain their advantages and Umitations in the context of the analysis of enzyme-responsive materials, explanations of the working principles of the techniques will not be provided and the reader is referred to other specialised textbooks on this topic instead. 

Although a few mechanisms have so far been proposed to explain the antimicrobial properties exhibited by proanthocyanidins (e.g., inhibition of extracellular enzymes) [86], Jones et al. [83] postulated that their ability to bind bacterial cell coat polymers and their abihty to inhibit cell-associated proteolysis might be considered responsible for the observed activity (Table 1). Accordingly, despite the formation of complexes with cell coat polymers, proanthocyanidins penetrated to the cell wall in sufficient concentration to react with one or more ultra-structural components and to selectively inhibit cell wall synthesis. Decreased proteolysis in these strains may also reflect a reduction of the export of proteases from the cell in the presence of proanthocyanidins [83]. 

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