*3.4. Patch Characterization*

Previous work highlighted that patches realized starting from a hydrogel based on NaCMC (2% *wt.*/*wt.*) as bioadhesive polymer, glycerol (10% *wt.*/*wt.*) as a plasticizing agent, hydrotalcite ZnAl-NO3 (1% *wt.*/*wt.*), and water (until 100%) shows suitable mechanical properties for topical use [23]. Using this composition, a new hydrogel was prepared using ZnAl-KET 1% *wt.*/*wt.* in place of ZnAl-NO3. The patch was prepared to cast the hydrogel in a circular mold, obtaining a final formulation with a surface area of 10.17 cm2, a final weight of 0.54 g <sup>±</sup> 0.01 (0.0532 g/cm2), and a thickness of 414 <sup>μ</sup><sup>m</sup> <sup>±</sup> 7.42. Considering the loading percentage of ZnAl-KET (41.89% *wt.*/*wt.*), the amount of KET/surface was measured to be 1.44 mg/cm2.

Taking into account this datum, the patch can be prepared in different sizes to be applied on surfaces of different dimensions, as demonstrated in the pictures reported in Figure 5.

**Figure 5.** Examples of different sizes and shapes on which it can be applied the patch loaded with ZnAl-KET.
