2.3.3. Swelling Behavior

To evaluate how much solution could be loaded into the synthesized hydrogels, a series of 5 aqueous solutions with adjusted pH values of 2, 4, 6, 7, and 8 (with NaOH and HCl) was prepared. Subsequently, an amount of each synthesized hydrogel was weighed in triplicate and each portion was placed in one of the previously prepared aqueous solutions with a different pH. Then, each hydrogel was removed from the aqueous solutions and weighed (excess water on the surface of the hydrogel was previously removed with wipes) every 10 min for 30 min. Finally, the swelling percentage was determined using the following expression:

where W is the hydrogel weight after a certain time and W₀ is the initial hydrogel weight. The statistical analysis to evaluate the loading capacity of the hydrogels consisted of a design relying on two factors (hydrogel composition and pH) and was applied with 2 and 5 levels, respectively, in which the dependent variable, the swelling percentage, was evaluated in triplicate. IBM SPSS Statistics 27.0.0 versión software was used to carry out the analysis and consisted of a two-way ANOVA with α = 0.05, where the assumptions of normality and homoscedasticity were corroborated by the Shapiro–Wilk and Levene tests, respectively. To verify the statistical differences between the pH levels, Tukey’s multiple comparison test was used with a significance of 0.05.