Research Opportunities: academic year

Smith: Research in Biology

Andy Smith      

Our research takes a biomimetic approach to the study of biological adhesives.  The glues that we study have unusual and highly desirable properties that would make them excellent medical adhesives.  Our goal is to determine the structure of these glues and how their structure creates such impressive performance.  From there, it may be possible to mimic the natural design to make a similar synthetic adhesive.  Many animals, especially snails and slugs, can form strong attachments using dilute gels.  Limpets, for example, can often glue themselves onto rocks so firmly that one needs tools to pry them off.  Also, certain species of slugs produce a defensive glue that is remarkably sticky and tough.  These gels are particularly impressive because they consist of roughly 97% water, and appear to be modifications of the normal lubricating slime the animals secrete.  Furthermore, the glues can stick to wet, slippery, flexible surfaces that confound artificial adhesives. 

We are interested in how animals can convert dilute, lubricating gels into strong adhesives.  We have found specific, gel-stiffening proteins that drive this change.  The function of these proteins, and the integrity of the glue overall, depends on the presence of metals.  Iron, copper, zinc and calcium are common in the glue, and play different roles.  They can cross-link polymers directly, and they can catalyze oxidative cross-linking.  The cross-links stiffen the glue, causing it to set.  Nevertheless, stiffness alone is not sufficient; the glues must be tough.  We have demonstrated that slug glue gains its toughness from the interactions of two distinct polymer networks.  There is a stiff protein network, and a deformable carbohydrate network.  These two networks work together synergistically to generate drastic increases in toughness.  This is referred to as a “double network” mechanism.

We use four major approaches to study these glues:

  • We use biochemical tools to identify and characterize the proteins, polysaccharides and metals present in the glue.
  • We use biochemical and mechanical methods to test how these different components contribute to glue performance.  Specifically, we manipulate components of the glue and measure the impact of the changes on glue mechanics.
  • We study tissue sections of the secretory epithelium in order to gain insight into how the glue is assembled.
  • We create novel gels using commercial components that mimic the natural glue’s components, in order to test hypotheses of mechanism and ultimately to guide the synthesis of a biomimetic glue.


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