The Gradient Foam Cement of the Sandcastle Worm as a Model for New Materials

University Of Utah, Salt Lake City UT

Investigators

Abstract

ID: MPS/DMR/BMAT(7623) 0906014 PI: Stewart, Russell ORG: University of Utah Title: The Gradient Foam Cement of the Sandcastle Worm as a Model for New Materials INTELLECTUAL MERIT: The sandcastle worm Phragmatopoma californica resides for physical protection in a composite mineral shell in the intertidal zone along the coast of California. The worm gathers the mineral component adventitiously as sand grains and bits of seashell hash which it bonds together into a tube with small dabs of a proteinaceous glue in the manner of building a stone wall. The glue sets within 30 s under cold seawater and hardens to a tough leathery consistency through oxidative crosslinking. Technological interest in this bioadhesive stems from its ability to bond a diverse range of mineral substrates under water. The adhesive is secreted as a colloidal suspension with low initial viscosity and interfacial tension that readily spreads on wet substrates, yet it is sufficiently cohesive that it does not disperse into the ocean before setting. Moreover, the water-borne bioadhesive apparently displaces interfacial water, a prerequisite for strong surface adhesion. These properties make the P. californica adhesive a valuable new paradigm for the design of water-borne, underwater adhesives. Several questions remain to be answered about the composition and biological processing of the adhesive. To illustrate, the adhesive gland contains at least two distinct types of secretory granules. (1) How are the glue proteins distributed between the granule types? (2) Are the glue proteins of each granule type expressed in distinct regions of the adhesive gland? (3) Does the mixing of the granule contents during secretion trigger the setting and curing reactions. Experiments have been devised to analyze the composition and biological processing of the adhesive before it sets. The first set of experiments (aim 1) will provide a broad overview of adhesive gland physiology through gene expression analysis. The second set of experiments (aim 2) will use the genetic and antibody probes resulting from aim 1 to investigate functional partitioning of the adhesive gland by examining spatial expression patterns. The third set of experiments (aim 3) will deploy powerful methods and modern mass spectrometry instrumentation to analyze the protein content of freshly secreted adhesive and of individual secretory granules. Peptides will be proteolytically generated and analyzed by micro-liquid chromatography and tandem mass spec (LC/MS/MS). Proteomic analysis will provide direct evidence that the new glue proteins discovered in the expression survey are present in the glue. BROADER IMPACTS: The results of these studies will make progress towards solving important technological issues such as 'wet bonding' of bone-to-bone or bone-to-metal in implants using injectable and biocompatible adhesives as well as other 'under water' adhesive applications." Integration of teaching and research is achieved in a novel and effective way. The majority of the P. californica adhesive gland EST (expressed sequence tags) database will be developed during an undergraduate laboratory course in Molecular Bioengineering where students learn about construction cDNA libraries, purifying plasmids, automated DNA sequencing, bioinformatics resources, and how these tools are used to investigate biological processes. Students find this experience quite unique compared to canned laboratory exercises. The results are not known before hand, and the students have an authentic opportunity to discover new biotechnological resources. Students take ownership of the genes they are investigating, pursue the bioinformatics analysis, and develop hypotheses about the potential role of their gene in the bioadhesive.