Department of Health Science and Technology, ETH Zürich, 8092, Zürich, Switzerland.
Department of Materials, ETH Zürich, 8093, Zürich, Switzerland.
Sci Rep. 2018 Jun 29;8(1):9867. doi: 10.1038/s41598-018-27975-0.
The defensive slime of hagfish consists of a polyanionic mucin hydrogel that synergistically interacts with a fiber network forming a coherent and elastic hydrogel in high ionic strength seawater. In seawater, the slime deploys in less than a second entrapping large quantities of water by a well-timed thread skein unravelling and mucous gel swelling. This rapid and vast hydrogel formation is intriguing, as high ionic strength conditions generally counteract the swelling speed and ratio of polyelectrolyte hydrogels. In this work we investigate the effect of ionic strength and seawater cations on slime formation dynamics and functionality. In the absence of ionic strength skeins swell radially and unravel uncontrolled, probably causing tangling and creating a confined thread network that entraps limited water. At high ionic strength skeins unravel, but create a collapsed and dense fiber network. High ionic strength conditions therefore seem crucial for controlled skein unraveling, however not sufficient for water retention. Only the presence of naturally occurring Ca or Mg-ions allowed for an expanded network and full water retention probably due to Ca-mediated vesicle rupture and cross-linking of the mucin. Our study demonstrates that hagfish slime deployment is a well-timed, ionic-strength, and divalent-cation dependent dynamic hydrogel formation process.
八目鳗防御黏液由多阴离子黏蛋白水凝胶组成，该水凝胶与纤维网络协同作用，在高离子强度海水中形成具有粘弹性的水凝胶。在海水中，黏液不到一秒钟即可展开，通过适时解开线轴并使黏胶膨胀，从而捕获大量的水。这种快速而广泛的水凝胶形成过程很有趣，因为高离子强度条件通常会对抗聚电解质水凝胶的溶胀速度和比率。在这项工作中，我们研究了离子强度和海水中阳离子对黏液形成动力学和功能的影响。在没有离子强度的情况下，线轴会径向膨胀并失控解开，这可能导致纠缠并形成受限的线轴网络，从而限制水的捕获量。在高离子强度下，线轴会解开，但会形成坍塌且致密的纤维网络。因此，高离子强度条件对于控制线轴解开似乎至关重要，但不足以保持水分。只有存在天然存在的 Ca 或 Mg 离子才能使网络扩展并完全保留水分，这可能是由于 Ca 介导的囊泡破裂和黏蛋白的交联。我们的研究表明，八目鳗黏液的展开是一个时机恰到好处、依赖于离子强度和二价阳离子的动态水凝胶形成过程。
