Effects of different stimuli on the properties of a triple-crosslinked hydrogel

• Main Author: Yip, Ying
• Other Authors: Tan Lay Poh
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/167241
• Institution: Nanyang Technological University

Hydrogels with multiple modes of crosslinking have emerged as promising candidates for biomedical applications due to their improved mechanical properties using multiple stimuli. In this study, branched thermoresponsive copolymer with amine end groups (PPG-PEI) was crosslinked with oxidized alginate (OA) and Ca2+ to form dual-crosslinked (PPG-PEI-OA) and triple-crosslinked hydrogels (PPG-PEI-OA(Ca2+)), which demonstrated responsiveness to temperature, pH, and Ca2+ stimuli. Higher degree of oxidation of alginate reduced the molecular weight of OA, decreasing the thermal stability and gel stiffness. The combination of thermal-induced and Schiff base crosslinking significantly improved mechanical stiffness of hydrogel, while the subsequent addition of Ca2+ unexpectedly reduced stiffness due to swelling. Furthermore, higher pH values improved the gel stiffness of the crosslinked hydrogels. Expectedly, PPG-PEI-OA(Ca2+) showed slower protein release and degradation rates compared to PPG-PEI-OA, indicating that the additional Ca2+ crosslinking decreased the hydrogel’s mesh size and enhanced its stability. This suggests that hydrogels with multiple crosslinks in response to different stimuli have potential for a range of biomedical applications, allowing the users to control each parameter to achieve a gel with their desired stiffness, degradation and drug release speed for their specific applications.