**2.6 Enzyme sensitive polymeric material**

Some fundamental guidelines should be followed while synthesizing enzyme-sensitive polymers with biomedical utilization. Enzymes must work in certain settings (e.g., an aquatic milieu having multiple ions with a pH of 7.4 or mildly basic or acid), while enzyme-sensitive polymers must withstand these circumstances. Apart from the availability of a substrate/substrate-mimic molecule for such focused enzyme to respond, the focused enzymes' operations must cause a variation in the polymers' characteristics for the particular activities to occur. The activity of the enzyme and the reaction of the final substance can be performed concurrently or in a step-by-step manner. For instance, proteins were used as a crosslinking agent in the DNA nanoparticles, and proteases quickly degrade the protein, destroying the nanoparticles [54]. In some other cases, enzymatic dissociation of a protective moiety causes peptides generated from amyloid to fold, reorganize, and self-assemble forming fibrillar clumps [55].

In live organisms, enzymes govern the bond generation and breakage, substrate oxidation/reduction, as well as isomerization processes, with the first two chemical reactions being exploited in the development of enzyme-sensitive materials. The bond breakage process has been utilized to cleave protein as well as ester bonds with polymers and/or tiny moiety, which really is important in controlled medication delivery with implant biodegradation. The kinase/phosphatase combination, which catalyzes the dephosphorylation/phosphorylation events here on substrates, might be employed to build reversibly sensitive materials through enzymatic bond creation and breaking.

Chitosan, alginate, dextran, polyethylene glycol, polyacrylamide, and polyethylene oxide have all been investigated as polymer matrices for the creation of enzymesensitive systems (butyl methacrylate) (**Figure 4**) [56–58].
