Biomedical Engineering Reference
In-Depth Information
Some reports suggest that proteins may play an important role in the adhesion of Cuvierian
tubules from
H. forskåli
(DeMoor et al., 2003; Flammang & Jangoux, 2004; Müller et al., 1972).
For example, the adhesive residue left when tubules are peeled from a surface consists
mainly of protein (DeMoor et al., 2003), and the treatment of tubules with proteases causes
loss of adhesion (Müller et al., 1972). However, it has been reported that the proteins most
likely differ between species (Flamman & Jangoux, 2004), making further comparative
biochemical surveys important for elucidating the mechanism.
The effect of urea on tubule-glass adhesion showed that bond strength decreased
progressively with increasing urea concentration until it was completely lost at 2 M urea
(Figure 7). However, if tubules that had been incubated for about 60 sec in 2 M urea were
then rinsed for about 60 sec in simulated sea water, some adhesion was restored, although
the extent was rather variable. Urea disrupts hydrogen bonding, and its effect on adhesion
may reflect some partially reversible protein unfolding (Zahn et al., 1972). The rapidity and
partial reversibility of the effect indicates that there is not a complete urea-mediated release
of proteins from the tubule surface.
Fig. 7. The effect of different washing solutions on the adhesiveness of
H. dofleinii
Cuvierian
tubules for glass. (C) The effect of urea concentration, where ▲ indicates conditions where
the force per unit width exceeded 0.05 N/mm.
4. Conclusion
The distinct features of the Cuvierian tubule adhesion mechanism, especially its rapid action
under water, are unique. If the mechanism can be understood, then it may be possible to
design a synthetic system with analogous properties. An adhesive that provided instant grip
in an aqueous environment would be very valuable, especially in medical applications, as
the majority of existing adhesives bind well only to dry surfaces.
It appears that although the tubules of
H.dofleinii
are distinct from those of other species,
especially in their size and the number expelled, the adhesive properties of these Cuvierian
tubules (including preferences for hydrophilic surfaces, pH optima, etc.) are similar to those
found in other species, even if mechanistic details may differ between species as has been
proposed previously (Flammang and Jangoux, 2004). It is thought that during expulsion and
tubule elongation, granular cells that are internal in the pre-release tubule become located
