**2.4 Polymers that respond to glucose**

Glucose-sensitive polymers can imitate typical internal insulin production, reducing diabetes problems and allowing for regulated delivery of the bioactive chemical. These really are sugar responsive and exhibit a wide range of responses to glucose. Although their applicability for both glucose monitoring and insulin administration, such polymers have gotten a lot of interest. Despite these benefits, the main drawbacks are the quick reaction time as well as the possibility of nonbiocompatibility. The following techniques have been used to build glucose-sensitive polymeric-based formulations: enzymatic oxidation of glucose using glucose oxidase, glucose binding using lectin, or reversible covalent bond creation using phenylboronic acid molecules. Glucose responsiveness is caused by the polymer's reaction to the by-products produced either by oxidation (enzymatic) of glucose. Glucose oxidase (GOx) is oxidized to form glucose to produce gluconic acid with hydrogen peroxide (H2O2). Within the instance of poly (acrylicacid) coupled with GOx mechanism, for instance, when blood glucose levels rise, conversion of glucose to gluconic acid, causing a drop in pH enabling hydrogenation of PAA carboxylate groups, allowing insulin to be released more quickly. Because its release profile closely resembles that of internal insulin, this approach is gaining popularity [45, 46].

Another technique makes use of lectin's specific carbohydrate-binding characteristics to create a glucose-responsive system. Lectins are bifunctional proteins, and their glucose-biding function allows them to produce a variety of glucosesensitive materials. The responses of these mechanisms were unique to glucose and mannose, with no reaction to certain other sugars. Concanavalin A is a 4 bindingsite lectin that has been widely employed in insulin-containing medication delivery. The insulin component is chemically changed by inserting functional moieties (or glucose molecule) and afterward connected to a transporter or support via particular interactions that can only be disrupted by the glucose it in this sort of system. Concanavalin A competitive binding characteristic to glucose as well as glycosylated insulin is exploited in the glycosylated insulin-Concanavalin A combination. The bioactive unbound glucose moieties cause glycosylated Concanavalin A-insulin complex to be displaced inside the surrounding structures. The production of single-substituted glucosyl terminal PEG with insulin complex was also described in other investigations. The G-PEG–insulin complex was covalently coupled to Concanavalin A, which was connected to a PEG–poly(vinylpyrrolidoneco-acrylic acid) framework, and when the levels of sugar grew, the competitive attachment of glucose to Con A caused the G-PEG insulin complex to be displaced and released (**Figure 3**) [47].

**Figure 3.** *Polymers that respond to glucose in a variety of ways.*
