“…However, these interactions depend significantly on the protonation state of the functional groups of the polymer, which are closely related to the pH [87]. Consequently, the more acidic the environment is during the interaction, the higher degree of protonation on their surface the chitosan:TPP nanoparticles exhibit, which allows a greater number of interactions with the negatively charged mucosal compounds through the formation of polyelectrolyte complexes that enhance adhesion [88,89], as Figure 5a-c shows. Nevertheless, under neutral or alkaline pH conditions, the amino groups deprotonate, and the positive charges of chitosan are neutralized, forming an insoluble biopolymer layer that tends to precipitate, limiting its mucoadhesive properties [84,90,91], as Figure 5d the two biopolymers that influence an entanglement of mucin and polymer chains [82], causing the formation of a resulting polymeric network with an enhanced elastic modulus (G′) in comparison with the sum of the elastic modulus (G′) values of the single components [83].…”