Moses D N, Mattoni M A, Slack N L, Waite J H, Zok F W
Materials Department, University of California, Santa Barbara, 93106-5050, USA.
Acta Biomater. 2006 Sep;2(5):521-30. doi: 10.1016/j.actbio.2006.05.002. Epub 2006 Jul 10.
The remarkable mechanical prowess of the jaws of the bloodworm Glycera dibranchiata appears to be a consequence of a robust cross-linked network of organic molecules, notably melanin and proteins, as well as small amounts of unmineralized Cu and a Cu-based mineral. The present study focuses on the role of melanin. Mechanical properties of untreated jaws and the constituent melanin are probed through nanoindentation, both in air and underwater. Complementary information is obtained from density and porosity measurements and attempts at Cu removal from the jaws using EDTA, an effective metal chelator in most biological systems. In near-tip regions of the jaws, mechanical properties attain the highest values and diminish only slightly when wet (by 15-25%), in contrast to the behavior of other organic biomaterials. The melanin constituent contributes significantly to the mechanical integrity of the jaw; its hardness and elastic modulus are about half those of untreated jaws. Although melanin may be the dominant shape-determining component of the structure, it remains to be shown whether jaw assembly is mediated by protein deposition on a melanin scaffold or, conversely, by melanin deposition on a protein scaffold. The inability of EDTA to chelate Cu from the jaws and the relatively high density of the jaws and the melanin support the notion of a highly cross-linked molecular structure. Finally, based on the metric H(3)/E(2) (H being hardness and E the Young's modulus), the results suggest that the abrasion resistance of the jaws is superior to all engineering polymers and competitive with the hardest metallic alloys.
血蠕虫双须矶沙蚕（Glycera dibranchiata）颚部卓越的机械性能似乎源于一个由有机分子构成的强大交联网络，特别是黑色素和蛋白质，以及少量未矿化的铜和一种铜基矿物质。本研究聚焦于黑色素的作用。通过纳米压痕技术，在空气和水下环境中探究了未处理颚部及其组成成分黑色素的机械性能。从密度和孔隙率测量以及使用乙二胺四乙酸（EDTA，大多数生物系统中一种有效的金属螯合剂）从颚部去除铜的尝试中获得了补充信息。在颚部的近尖端区域，机械性能达到最高值，并且在湿润时仅略有下降（下降15 - 25%），这与其他有机生物材料的行为形成对比。黑色素成分对颚部的机械完整性有显著贡献；其硬度和弹性模量约为未处理颚部的一半。尽管黑色素可能是该结构中决定形状的主要成分，但颚部的组装是由蛋白质沉积在黑色素支架上介导，还是相反地由黑色素沉积在蛋白质支架上介导，仍有待证明。乙二胺四乙酸无法从颚部螯合铜，以及颚部和黑色素相对较高的密度支持了高度交联分子结构的观点。最后，基于H(3)/E(2)指标（H为硬度，E为杨氏模量），结果表明颚部的耐磨性优于所有工程聚合物，并且与最硬的金属合金相当。
