Biomedical Engineering Reference
In-Depth Information
cm
a
b
c
m
Hard
Self-made
Soft
Self-made
Hard
Foreign
cm
m
Hard
Foreign
Hard
Foreign
m
Hard
Foreign
Fig. 9.1 Different modes of attachment among different sessile organisms: ( a ) mussel, ( b )
tubeworm, and ( c ) barnacle
Table 9.2 Comparison of biological adhesives among three model organisms
Mussel
Barnacle
Tube worm
Taxonomy
Mollusk
Crustacean
Annelida
Role of attachment
Holdfast
Holdfast
Tube building
Protein/Fe 3 þ /Ca 2 þ
Protein/Ca 2 þ /Mg 2 þ
Sort of components
Protein
Number of proteins
6 in the disk
> 6
3
Protein-modification
DOPA/PhoSer/HyArg/Hyp etc. Glycosylation
DOPA/PhoSer
Cross-linking
Involved
Unknown
Involved
Macro-structure
Thread/disk
Homogenous
Homogenous
Microstructure
Solid foam, granular cuticle
Fused granule
Solid foam
Protein localization
Functional localization
Unknown
Unknown
Distance of attachment 2-4 cm
> 1 m m
10-20 m m
Fresh start of adhesive Possible
Impossible
Possible
Adherends
Foreign/end of thread
Foreign/base shell Foreign/foreign
overcome difficulties in firm and durable underwater attachment. There are
differences and similarities in macroscopic and molecular levels of the underwater
adhesives (Table 9.2 ). Studying them could reveal essential functionalities in under-
water attachment, clarify reasons for diversified ways to overcome obstacles for
underwater attachment, and provide hints for potential best combinations that we
can use. The individual adhesive systems used by the three organisms are
summarized in the following three sections.
9.4 Overview of the Mussel Byssal Holdfast
The mussel is a bivalve and attaches to material surfaces by forming several byssal
threads [ 5 ]. The animal hangs down by its byssus or sits on a trampoline made by
byssus (Fig. 9.1 ). Occasionally, a mussel will move its habitat by cutting off its
byssus at the proximal stem, thus the thread is disposable. Simply, their main
body is a few centimeters away from foreign material surface separated by the
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