Characterizing and mimicking marine biomaterials and developing a method for making protein-based adhesives

Jessica K Roman, Purdue University

Abstract

Biological organisms demonstrate remarkable abilities to affix themselves to almost any surface. Many marine organisms, for instance, are able to synthesize strong adhesive materials to withstand the rough costal conditions. The common blue mussel (Mytilus edulis) illustrates this in their cross-linked, protein-based glue. Not only are these “plaques” strong enough to hold the animal in place, but the soluble precursor proteins also cure in a wet setting environment, a feature with which commercial glues continue to struggle. Characterization of this intriguing material shows high levels of the amino acid 3,4-dihyroxyphenylalanine (DOPA), which is believed to be responsible for the cross-linking and adhesive properties. Peptide mimics of marine mussel adhesives were prepared and cross-linked to obtain atom-by-atom level insights on the chemical cross-links giving rise to the performance of this biological material. Made via a cross-linking mechanism, soybean protein and bovine serum albumin adhesives have been produced through a single step process and are capable of high strengths on both wood and aluminum adherends. The current methods for introducing adhesive properties to protein systems include significant modifications to the protein and the introduction of synthetically functionalized polymer resins, both of which are more expensive than the method proposed. Due to cost, it has been difficult replacing carcinogenic, formaldehyde-based adhesives. However, the proposed method is low cost, non-toxic, requires no modifications or additions to the protein system and requires no additional processing prior to use. Developing a strong, renewable, and non-toxic adhesive will solve many of the adhesive industries current problems, being competitive in many adhesive markets, from surgical to wood to automotive adhesives. Chitons, marine mollusks that feed primarily on algae growing on rocks, have evolved a ribbon-like rasping tongue designed with numerous rows of extremely hard, wear-resistant teeth. These remarkable properties arise from the incorporation of nanocrystalline magnetite (Fe3O4) into a nanofibrous chitin scaffold. Like many biomineralizing organisms, chitons do not form magnetite by classical ion-by-ion crystal growth. Instead, mineralization originates with deposition of a disordered metastable precursor, ferrihydrite, which is subsequently transformed into magnetite. This remarkable polymorph selectivity has been difficult to reproduce in the laboratory, especially the precipitation of ferrihydrite under mild conditions. Using a combination of X-ray absorption and EPR spectroscopy, organic-iron complexes have been identified in the early stages of mineralization. In vitro experiments demonstrate these complexes facilitate the formation of ferrihydrite under physiological conditions, while completely suppressing the formation of thermodynamically stable crystalline lepidocrocite in the presence of acidic organic molecules, which complex iron.

Degree

Ph.D.

Advisors

Wilker, Purdue University.

Subject Area

Biochemistry|Polymer chemistry

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