Influence of Novel Crosslinker on the Properties of the Degradable Thermosensitive Hydrogels

Summary A novel degradable crosslinker, N, N′-bis(acryloyl) cystamine (BACy), was synthesized with cystamine dihydrochloride (Cy) and acryloyl chloride. Then three series of degradable thermosensitive hydrogels with different crosslinker contents were prepared from N-isopropyl acrylamide (NIPAAm), BACy (Bx-series) or N, N′-methylene-bis-acrylamide (NMBA)(Nx-series) or equimolar BACy and NMBA (BNx-series) as crosslinker, and diethoxyacetophenone (DEAP) as photoinitiator under UV-irradiation polymerization. The effect of crosslinker content on the properties of the hydrogels such as swelling behavior and mechanical properties was investigated. At the same time, their degradabilities were investigated by dissolving them into different concentrations of cysteine solution. The results show that the swelling ratios for the Bx-series hydrogels are lower than those for the Nx-series hydrogels. But, after degradation in the cysteine solution, the swelling ratios for the Bx-series hydrogels were greater than those for the Nx-series hydrogels. When the crosslinker content was increased, all values of shear stress (τ), shear modulus (G), and effective crosslinking density (ρX) increased. But, the ρX values for the reduced Bx series and BNx series hydrogels were lower than those for original hydrogels. Results also showed that the ρX values for the Nx series hydrogel were not affected by cysteine. The disulfide bonds of BACy in these novel hydrogels were decomposed (reduced) in the cysteine solution and converted into thiol group. These thiol groups could be used to absorb some metal ions such as silver ion. Hence, the absorption of silver ion for the hydrogel with thiol group was also investigated in this research.