A nonmineralized approach to abrasion-resistant biomaterials.
The tooth-like mouthparts of some animals consist of biomacromolecular scaffolds with few mineral components, making them intriguing paradigms of biostructural materials. In this study, the abrasion resistance of the jaws of one such animal, the bloodworm Glycera dibranchiata, has been evaluated by nanoindentation, nanoscratching, and wear testing. The hardest, stiffest, and most abrasion-resistant materials are found within a thin (<3 microm) surface layer near the jaw tip and a thicker (10-20 microm) subsurface layer, both rich in unmineralized Cu. These results are consistent with the supposition that Cu ions are involved in the formation of intermolecular coordination complexes between proteins, creating a highly cross-linked molecular network. The intervening layer contains aligned atacamite [Cu(2)(OH)(3)Cl] fibers and exhibits hardness and stiffness (transverse to the alignment direction) that are only slightly higher than those of the bulk material but lower than those of the two Cu-rich layers. Furthermore, the atacamite-containing layer is the least abrasion-resistant, by a factor of approximately 3, even relative to the bulk material. These observations are broadly consistent with the behavior of engineering polymer composites with hard fiber or particulate reinforcements. The alignment of fibers parallel to the jaw surface, and the fiber proximity to the surface, are both suggestive of a natural adaptation to enhance bending stiffness and strength rather than to endow the surface regions with enhanced abrasion resistance.
Pontin
Michael G
MG
Materials Department, University of California, Santa Barbara, CA 93106-5050, USA.
Moses
Dana N
DN
Waite
J Herbert
JH
Zok
Frank W
FW
D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008903:Minerals / Q000737:chemistry; D011077:Polychaeta / Q000648:ultrastructure
D001672:Biocompatible Materials; D008903:Minerals
J Exp Biol. 1999 Dec;202(Pt 23):3285-94
10562511
Science. 2002 Oct 11;298(5592):389-92
12376695
Naturwissenschaften. 2002 Dec;89(12):579-83
12536282
Science. 2003 Aug 22;301(5636):1049; author reply 1049
12933994
J R Soc Interface. 2007 Feb 22;4(12):19-31
17015290
J Exp Biol. 2006 Aug;209(Pt 16):3219-25
16888069
Acta Biomater. 2006 Sep;2(5):521-30
16831576
J Biol Chem. 2006 Nov 17;281(46):34826-32
16984906
Bull Biol Fr Belg. 1973;107(4):301-21
4793660