Meso-2,3-dimercaptosuccinic Acid–Based Macromers for pH-Sensitive Degradable Hydrogels

One way of tailoring the properties of hydrogels is using functional cross-linkers. In this study, four highly water-soluble and degradable carboxylated diacrylate and diacrylamide macromeric cross-linkers were designed as precursors to prepare pH-sensitive and degradable hydrogels. The macromers were synthesized from thiol-Michael addition reaction of meso-2,3-dimercaptosuccinic acid (DMSA) with poly(ethylene glycol) diacrylate (PEGDA, M n = 575 g/mol) or N, N ′-methylene bis(acrylamide) (MBA) in the presence of triethyl amine or sodium hydroxide. They were used as cross-linkers in fabrication of 2-hydroxyethyl methacrylate (HEMA)-based hydrogels, whose swelling strongly depended on pH, macromer structure, and hydrogel composition. The degradabilities of the hydrogels were greatly enhanced by increasing the concentration of the cross-linkers. The mechanical properties of the hydrogels can be tuned by tailoring the cross-linking macromer. The hydrogels were proven to have metal chelating ability in the context of Fe 3+ ions, and upon this chelation, Young’s modulus was also observed to increase significantly. In vitro cytotoxicity evaluations against U-2 OS human bone osteosarcoma epithelial cells and C2C12 mouse myoblast cells showed that the PEGDA functional macromers are not toxic.