*2.3. Synthesis of DAC*®

DAC® copolymer was synthesized by esterification of HA with PLA according to the experimental protocol already registered by Novagenit [20]. In order to allow the grafting of PLA to HA, PLA was reacted with carbonyl di-imidazole to obtain the corresponding imidazole derivative (PLA-CI). Subsequently, the reaction between carboxyl-activated PLA and an organic soluble HA form (Hyaluronic acid tetrabutyl ammonium salt, HA-TBA) is carried out in N-methyl pyrrolidone (NMP), 48 h, 37 ◦C; finally, precipitation and ion exchange lead to the sodium salt form of HA-g-PLA. The final derivatization grade is PLA/(HA + PLA) = 13% *w*/*w*.
