Barnacle adhesives

It is very well known that the type into which a cell is differentiated is determined by the interaction of the cell surface with its (macro) molecular environment (e.g.. Refs. [19, 20]). It is shown below that the supramolecular structure of barnacle adhesive, which is an extracellular matrix, is also formed through surface interactions. 

Fig. 10.1 SEM images of various appearances of the supramolecular structure of barnacle adhesive (a) thin sheet of densely arranged nanometer-sized adhesive globules on aluminum foil (b) sponge-like appearance of adhesive with the tendency to form strands on a self-polishing coating (c) web-like adhesive of loosely matted strands on a PDMS coating.

Barnacle adhesive M. edulis increas e in volume (water uptake), low adhesion strength [2, 21, 29]... 

Theoretical Colloid Approach to Structure Formation in Barnacle Adhesive... 

The process of structure formation of barnacle adhesive can be further discussed in the light of a biocoUoidal system The characteristics of biocolloids are based on the principle of self-organization [47]. 

It may be conceivable that the structure formation of barnacle adhesive is determined by critical self-assembly concentrations of the adhesive proteins within an interfacial gap between a barnacle base and a substrate. It can further be suggested that the biopolymers form coherent gel structures, in which two transitions of critical protein concentrations determine the arrangement of adhesive globules from a dense sheet-like formation to a slightly loose sponge-like formation to a very loose branched or web-like structure. 

The consideration outlined above agrees with the assumption that substrates influence the structure formation of barnacle adhesive indirectly via properties that hold the barnacle base at a distance from the surface (e.g., fiber coatings, thick biofilm layers) or cause large interfacial gaps (e.g., PDMS coatings). These factors affect the concentration in the dispersion, and hence the position on the adsorption isotherm as compared to the micellar or hemi-micellar concentration, by impinging on the interfacial volume that needs to be filled with adhesive. 

Knowledge of the structure of barnacle cement within colloidal dimensions has recently been gained. It is shown that the barnacle adhesive presents a useful tool for understanding and investigating formation of bioadhesive structures as colloidal systems. 

Kamino, K., 2013. Mini-review barnacle adhesives and adhesion. Biofouling 29, 735—749. 

Figure 2. Barnacle Adhesion Data for Various Coatings...

RTV topcoats containing either the ablative or tethered diphenyldimethylsiloxane copolymers were applied to steel panels previously coated with the epoxy and a tie layer developed at NRL (8), After the panels were allowed to cure for one week, they were deployed at both northeast and southeast static test sites for 9 months. Controls of RTV 11 and RTV 11 containing 10% free diphenyldimethyl siloxane oil were also immersed in these marine environments. The overall fouling coverage was recorded for the northeast site and barnacle adhesion values were measured for the southeast site. Results are shown below in Figures 8 and 9. 

The leach rate of silicone oil additives from the silicone topcoat was readily determined using radiolabeled oils in both fresh and marine water systems (9). Use of radiolabeled oils simplifies the study of their environmental partitioning, since each component of the matrix can be easily analyzed and quantified using radiometric detection. The approach was to synthesize radiolabeled polydiphenyl-dimethylsiloxane oil which is similar in composition to that used in determination of barnacle adhesion measurements (see Figure 2). Next, the oil was added to RTVll, catalyzed and applied to metal coupons which were subsequently suspended in fresh and salt water fish tanks. Coupons, soil and sediment were analyzed monthly for one year for mass balance determination. 

Biotechnology and genetic engineering provide one potential route. We can engineer bacteria, such as the common Escherichia coli (or E. coli) to actually produce proteins that they normally do not have. In this case, we might convince a bacterium to start cranking out mussel or barnacle adhesive proteins. This approach does have some... 

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