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CHEMISTRY 2000

CHEMISTRY 2000. Topics of Interest #4: Superglue from the Sea. Superglue from the Sea. Despite the many adhesives that have been developed in the last few decades, very few of them have been useful in medical applications such as repairing bone damage.

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CHEMISTRY 2000

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  1. CHEMISTRY 2000 Topics of Interest #4: Superglue from the Sea

  2. Superglue from the Sea • Despite the many adhesives that have been developed in the last few decades, very few of them have been useful in medical applications such as repairing bone damage. • Any adhesive that could be used to repair bones in situ: • must work in the presence of water at about 37 C • must not be made from toxic reactants, • must not produce toxic by-products, and • must not trigger an immune response. • A candidate adhesive has been developed at the University of Utah. It is based on a natural adhesive produced by sandcastle worms (Phragmatopoma californica). H. Shao, K.N. Bachus and R.J. Stewart Macromolecular Biosciences (2008 preview) DOI: 10.1002/mabi.200800252. Reported at http://esciencenews.com/articles/2008/11/24/superglue.sea

  3. Superglue from the Sea • While many sea creatures build their homes by secreting minerals to form a shell, sandcastle worms (see right) build their homes by gluing together existing sand and seashell fragments. • To this end, they secrete an adhesive consisting of protein strands (both acidic and basic) and lots of Mg2+ and Ca2+ cations. • This adhesive sets quickly (<30 seconds in cold sea water) and, while it is initially a watery liquid, it doesn’t significantly diffuse out into the bulk of the ocean. H. Shao, K.N. Bachus and R.J. Stewart Macromolecular Biosciences (2008 preview) DOI: 10.1002/mabi.200800252. Image from http://flickr.com/photos/ken-ichi/2874911334/

  4. Superglue from the Sea • So, how does this adhesive work? • The components of the adhesive are at about pH 5 while inside the worm. At this pH, the basic proteins have a positive charge while the acidic proteins are mostly neutral. • The pH of seawater is about 8.2. At this pH, the acidic proteins are deprotonated, giving them negative charges. H. Shao, K.N. Bachus and R.J. Stewart Macromolecular Biosciences (2008 preview) DOI: 10.1002/mabi.200800252. Reported at http://esciencenews.com/articles/2008/11/24/superglue.sea

  5. Superglue from the Sea • So, how does this adhesive work? • The positively charged basic proteins are attracted to the negatively charged acidic proteins, and the oxygen and nitrogen atoms in all of the proteins are attracted to the Mg2+ and Ca2+ cations (except, of course for the N+ atoms), helping to hold the mixture together tightly. • The adhesive sticks to surfaces like sand, shells and bone because those surfaces have negatively charged oxygen atoms that are attracted to the cations (Mg2+, Ca2+ and basic proteins). • The proteins can also “cross-link” in a variety of ways. That means that the chains are not only attracted together via intermolecular forces, they become held together by covalent bonds. After that, they cannot be pulled apart. • All this adds up to a strong glue that only works in aqueous conditions in a relatively narrow pH range of ~5-9 – perfect for medical applications like gluing shattered bones back together.

  6. Superglue from the Sea • Testing the strength of bone fragments that have been glued together and left underwater for 4 months: No swelling was observed (so the adhesive is not absorbing water). H. Shao, K.N. Bachus and R.J. Stewart Macromolecular Biosciences (2008 preview) DOI: 10.1002/mabi.200800252. Reported at http://esciencenews.com/articles/2008/11/24/superglue.sea

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