Characterisation of enzyme-responsive polymers

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. 

Non-imaging techniques can also provide information about the morphology or size of a particle in a liquid environment. Light scattering and X-ray diffraction techniques can also be used to obtain information about the shape and size of the material in an aqueous environment (Azagarsamy et al, 2009 Castelletto et al, 2010 Wang et al., 2010 Woodcock et al., 2011). Circular dichroism has been used to obtain information about the secondary structure of peptide-based ERMs (Ktihnle and Bomer, 2009 Mutter etal., 2004). 

When the polymer material is used as a scaffold (e.g., polymer hydrogels), its mechanical properties become important because cells are known to respond to the stiffness of a substrate. Rheology is commonly used to characterise the mechanical properties of polymer hydrogels and can equally be used to characterise ERMs (Chen et al., 2002 Kim and Healy,2003 Sanborn et al., 2002 van Dijk et al., 2010). In addition, to measure viscoelasticity on a micrometre scale, microrheology can be used. This method is able to measure local inhomogeneities in the material and is therefore able to measure inside small samples and cells (Yang et al., 2010). 

The toxicity and inflammatory response of the polymer are crucial characteristics of the enzyme-responsive material if it is to be used in a living 

Another important consideration is the cross-reactivity of the enzyme-sensitive functionality with other enzymes. Ideally, the enzyme-sensitive functionality should react only with the enzyme that it was designed for and show little to no sensitivity to other enzymes. Similar to the selectivity, the cross-reactivity with other enzymes can be explored by exposing the 

---