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Injectable Self-Healing Zwitterionic Hydrogels Based on Dynamic Benzoxaborole–Sugar Interactions with Tunable Mechanical Properties

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posted on 16.01.2018, 00:00 by Yangjun Chen, Wenda Wang, Di Wu, Masanori Nagao, Dennis G. Hall, Thomas Thundat, Ravin Narain
Dynamic hydrogels based on arylboronic esters have been considered as ideal platforms for biomedical applications given their self-healing and injectable characteristics. However, there still exist some critical issues that need to be addressed or improved, including hydrogel biocompatibility, physiological usability, and tunability of mechanical properties. Here, two kinds of phospholipid bioinspired MPC copolymers, one is zwitterionic copolymer (PMB) containing a fixed 15 mol % of benzoxaborole (pKa ≈ 7.2) groups and the other is zwitterionic glycopolymers (PMG) with varied ratios of sugar groups (20%, 50%, 80%), were synthesized respectively via one-pot facile reversible addition–fragmentation chain transfer (RAFT) polymerization. PMBG hydrogels were formed spontaneously after mixing 10 wt % of PMB and PMG copolymer solutions because of dynamic benzoxaborole–sugar interactions. The mechanical properties of nine hydrogels (3 × 3) with different sugar contents and pHs (7.4, 8.4, 9.4) were carefully studied by rheological measurements, and hydrogels with higher sugar content and higher pH were found to have higher strength. Moreover, similar to other arylboronic ester-based hydrogels, PMBG hydrogels possessed not only self-healing and injectable properties but also pH/sugar responsiveness. Additionally, in vitro cytotoxicity tests of gel extracts on both normal and cancer cells further confirmed the excellent biocompatibility of the hydrogels, which should be ascribed to the biomimetic nature of phosphorylcholine (PC) and sugar residues of the copolymers. Consequently, the zwitterionic dynamic hydrogels provide promising future for diverse biomedical applications.