*2.1. Substances*

L-α-phosphatidylcholine (Egg Yolk PC 99% TLC purity), dexketoprofen tromethamine (99% purity, mean molecular weight *M*<sup>w</sup> = 375.42 g/mol) and chitosan (*M*<sup>w</sup> = 310.0 g/mol, 3.26 polydispersity index, 79.7%*N*-de-acetylation degree) were purchased from Vanson

Chemicals, Redmond, WA, USA. Chitosan was dissolved in 0.5% (*v*/*v*) acetic acid solution with 99.5% purity purchased from the Chemical Company. The homogeneous 0.5% (*w*/*v*) chitosan solution was prepared by stirring at room temperature for 24 h and subjected to degassing by centrifugation at 1500 rpm for 30 min.
