NaOH is used to activate hydroxyl groups in hyaluronic acd. For example, to create cross-links using bis epoxides or di-glycedyl ethers that can react with activated hydroxyl groups (ether bonding). In such reactions, NaOH, in addition to activating of hydroxyl groups of hyaluron, also opens the epoxy rings of the cross linker. In addition, in alkaline conditions, the ether bond is preferred to the ester bond (ester bond :by the carboxylic groups of hyaluronan). because under alkaline conditions, hydroxyl groups will be stronger nucleophiles than carboxyls. I also suggest an article reviewing various reactions to the formation of hyaluronic acid hydrogels.

Article Chemical modifications of hyaluronic acid for the synthesis ...