4.3. Synthesis of Methacrylate-Functionalized Hyaluronic Acid, Chondroitin, and Chondroitin Sulfate

Methacrylated derivatives of HA, CS, and chondroitin (Ch) were synthesized. The DM is defined as the number of MA groups per 100 disaccharide units and expressed as a percentage. Two separate methacrylating agents were used to synthesize methacrylated CS(G)MA with different MA moieties, namely, glycidyl MA and methacrylic anhydride. The feed ratios of methacrylating agents to polysaccharide were calculated per mole of HA/CS/Ch monomeric unit.

For the methacrylation of CS with glycidyl MA, a previously published method was followed in which first the lipophilic tert-butyl-ammonium salt of CS was formed, after which the methacrylation was performed in DMSO as a solvent for 2 day at 50 °C.⁵ Molar feed ratios of glycidyl MA to CS-TBA disaccharide of 0.2, 0.4, 0.6, and 1:1 were used to produce CSGMA with increasing DM. For an extended analysis of the resulting CSGMA using NMR and HPLC techniques, see the text accompanying Figures S3 and S4.

A method for synthesis of HAMA functionalized with methacrylic anhydride in a water/DMF solution adapted by Abbadessa et al.⁶ was used to synthesize HAMA, CSMA, and chondroitin MA of various DM. For HAMA, methacrylic anhydride was added in molar feed ratios of 2.2:1 (anhydride/HA disaccharide). For the synthesis of CSMA and ChMA, the same procedure and concentrations as for the synthesis of HAMA were performed, with a molar feed ratio of 3:1 (anhydride/CS disaccharide or anhydride/Ch disaccharide) for both reactions. The DMs of the obtained HAMA, CSMA, and ChMA were determined using the HPLC method described below.