Detailed Description

Bio-glues

Bio adhesives are polymeric materials which are naturally produced from a variety of organisms and have adhesive properties. The monomers of the polymeric bio adhesives consist of a variety of substances, but proteins and carbohydrates are the most common.
Biological adhesion is a phenomenon present in many biological systems. Examples of organisms that produce adhesives can include bacteria, spiders, marine tubeworms, sea cucumbers, barnacles and mussels. These adhesives are well known for being very strong, durable and ecologically safe compared with human-made substances. On top of that, some of them can be applied in an aqueous environment being impervious to water and turbulent forces, they give rise for many qualitative applications.

How do mussels attach themselves to a surface?

At the basis of our project are proteins which are normally produced from blue mussels (Mytilus edulis). Blue mussels produce adhesives comparable in strength to human-made glues . However these adhesives have extra advantages like the absence of carcinogens (formaldehyde) and their ability to sustain adhesive under water. Byssus threads of the blue mussel attach to a (underwater) solid surface due to catechols on adhesive proteins.

The mussel’s byssus is an exogenous attachment structure which was first described in 1711 (Brown 1952 ). Byssus’ main role is the attachment of the organism to surfaces. The byssus is a bundle of extracorporeal threads. This bundle is at the proximal end attached to the mussel’s byssal retractor muscle and at the distal end to a surface by adhesive plaques.
Mytilus edulis has the ability to bind to a very broad range of materials, ranging from glass, plastics, metals, wood and Teflon to biological materials, such as biological tissues, organisms, and other chemical compounds or molecules. As a result, the adhesive abilities of mussels have been an inspiration for the production of the synthetic version of this biological glue.

The mussel attached by its byssus threads (Powel, 2009)

Mussels use a rather flexible method to attach to a surface; they spin a set of threads from an internal muscle to the surface, also known as stem. (Waite, 1983) (Waite,1992) The treads are 2 to 4 cm in length and attach to the surface by the use of plaques (diameter 2-3 mm). Thus, this plaque connects the substrate and the byssal thread. The specific adhesion is determined by the number of threads, which can go up to 30 to 50 threads per mussel. This will lead to a total attachment strength up to 400N. The plaque is divided into three sections. The first part is a pre-coating adhesive layer, which can attach to the surface. On top of this, the byssal threads are anchored in an open, cellular structure. (Benedict & Waite, 1986) The overall protection layer is formed by a “varnish”, which protects against enzymatic and chemical degradation. (Rzepecki & Waite, 1995)