School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University , Tianjin 300072, China.
Department of Chemical Engineering and Materials Science, Wayne State University , Detroit, Michigan 48202, United States.
ACS Appl Mater Interfaces. 2016 Apr 13;8(14):8956-66. doi: 10.1021/acsami.6b00912. Epub 2016 Mar 31.
Inspired by stimuli-responsive remarkable changes in consistency (hardening, softening, autolysis) of sea cucumbers, we synthesized a supramolecular polymer(SP) hydrogel directly by photoinitiated aqueous polymerization of N-acryloyl 2-glycine monomer bearing one amide and one carboxyl group on the side chain. The SP hydrogels doped with Ca(2+) demonstrated excellent mechanical properties-high tensile strength (∼1.3 MPa), large stretchability (up to 2300%), high compressive strength (∼10.8 MPa), and good toughness (∼1000 J m(-2)) due to cooperative hydrogen bonding interactions from amide and carboxyl together with Ca(2+) cross-linking. Responding to the change in pH and Ca(2+) concentration, the hydrogels could modulate their network stability and mechanical properties: at pH3.0 and higher Ca(2+) content, the hydrogel formed low swelling network which was stiff and stable; in alkaline or neutral buffer with lower content of or without Ca(2+), the hydrogel formed a highly swollen transient network, which was soft and eventually autolyzed. The reversible multiple noncovalent bonds enabled the hydrogels to achieve thermoplasticity, self-healability, and reusability. Notably, distinct formulations of hydrogels could be welded together under heating to form a gradient hydrogel. In vitro cytotoxicity assay and subcutaneous implantation indicated that the SP hydrogels were biocompatible and autolytic in vivo. The SP hydrogels may find applications as temporary biodevices for intestinal drug delivery or for injectable filling in assisting suturing small vessels.
受海参在受到刺激时其一致性（硬化、软化、自溶）发生显著变化的启发，我们通过光引发带有一个酰胺基和一个羧基的侧链的 N-丙烯酰基 2-甘氨酸单体的水相聚合，直接合成了超分子聚合物（SP）水凝胶。掺杂 Ca(2+)的 SP 水凝胶由于酰胺和羧基的协同氢键相互作用以及 Ca(2+)交联，表现出优异的机械性能-高拉伸强度（约 1.3 MPa）、大拉伸性（高达 2300%）、高压缩强度（约 10.8 MPa）和良好的韧性（约 1000 J m(-2))。响应 pH 值和 Ca(2+)浓度的变化，水凝胶可以调节其网络稳定性和机械性能：在 pH3.0 及更高的 Ca(2+)含量下，水凝胶形成低溶胀的网络，其刚性和稳定性较高；在碱性或中性缓冲液中，或在较低含量或不含 Ca(2+)的情况下，水凝胶形成高度溶胀的瞬态网络，其柔软并最终自溶。这种可逆的多重非共价键使水凝胶具有热塑性、自修复性和可重复使用性。值得注意的是，不同配方的水凝胶可以在加热下焊接在一起，形成梯度水凝胶。体外细胞毒性试验和皮下植入表明，SP 水凝胶具有生物相容性，在体内可自溶。SP 水凝胶可作为临时生物器件，用于肠道药物输送或用于协助缝合小血管的可注射填充。
