Biomimetic Applications of Mussel Adhesives Mussel Adhesive – Not Just For Sticking To Rocks! Avinash Narayana Wiko Nkema Stephanie Phelps ENBE453 - Wilson

Man-Made Adhesives Adhesive - substance capable of holding materials together by surface attachment; a bond that resists separation is formed between the substrates or surfaces (adherends) compromising the joint and work is required to separate them” (Ratner et al, 1996). Successful adhesion is based on the principle of molecular contact, and interaction of the adhesive and the adherends. Adhesives must be highly resistant to environmental degradative processes and should be as free from weakening defects, such as air voids and contaminants, as possible (Ratner et al, 1996).

Bioadhesives Developed as a means of enabling the advanced use of adhesives in biological applications. “Bioadhesives are involved in cell-to-cell adhesion, adhesion between living and nonliving parts of an organism, and adhesion between an organism and foreign substances” (Ratner et al, 1996). “The adhesive must be able to be spread on wet surfaces, provide adequate working time, develop and maintain adhesion, desirably provide homeostasis, facilitate wound healing, and maintain biocompatibility. Positive microbial action would be an additional advantage” (Ratner et al, 1996). May be used in wound closure and in the bonding of prosthetic devices in both medicine and dentistry; Applications may be both short-term and permanent, and may allow for degradation and absorption by the body.

Mussel attachment to surfaces The mussel uses its foot to attach itself to surfaces. Glands in the foot secrete proteins and rhythmic muscular contractions of the foot mix and shape those proteins into threads. The newly formed threads are deposited onto the substratum to form the beginning of the plaque and threads. The protein thread grows from the surface, through the foot, to the mussel. When the thread is formed, the mussel foot completely releases its hold. The mussel is now suspended from the thread, leaving the foot free to explore the substrate for a suitable place to attach a second thread, and so on.

Mussel attached to surface

Byssal threads and adhesive Byssal threads are a composite material in which anisotropic bundles of continuous collagen fibers are embedded in a microfibrillar matrix, all of which is surrounded by thin cuticle. Flanking the collagen domain on both sides are silk fibroin-like domains, similar to the primary sequence of spider dragline silk. His-rich regions are located at both ends of the silk fibroin domains. Dopa side chains are located at the end of the his-rich domain.

Single byssal thread

Mussel Adhesive Proteins (MAPs) Underwater glue that tethers marine organisms to their substrates Are secreted as fluids and undergo cross-linking or hardening reaction to form a solid adhesive plaque Adhesion and cross-linking characteristics of MAPs are attributed to forms of the L-amino acid L-3,4-dihyrdoxyphenylalanine (DOPA) Synthetic polymers produced by coupling DOPA anchor residues to biocompatible water-soluble polymers such as polyethylene glycol (PEG). Branched versions of these polymers rapidly cross-link into rigid PEG based hydro-gels that exhibit a variety of applications.

Applications of synthetic MAPs PEG-anchored by DOPA onto metal, metal oxide and semiconductor nano-particle surfaces render nano-particles resistant to aggregation under physiologic conditions. They can tolerate a range of physiologic conditions such as high salt environments, resist agglomeration, and permit minimally invasive drug delivery PEG anchored by DOPA onto gold substrate also creates non-fouling surfaces that limit protein adsorption and inhibit nonspecific cell adhesion and spreading making them ideal for biosensor and medical implants. A two sided sticky compound synthesized by Messersmith and his team could be potentially used as a tooth coating to prevent dental plaque, which is caused by bacterial infection.