Polymer Gets Sticky When Hit With Light
Materials
Science: Inspired by mussel proteins, the polymer could be a useful medical
adhesive
Mussels
secrete a protein that helps them stick to underwater surfaces like rock,
metal, or wood. Chemists have designed sticky polymers that mimic this protein,
but these materials quickly set when exposed to air. To get more control with
these adhesives, researchers from Japan have developed a mussel-mimicking
polymer
that sets only when hit by light (ACS Macro Lett., DOI: 10.1021/mz300524q). The polymer could be used as an adhesive
for biomedical devices such as stents, the researchers say.
Mussel
adhesion proteins are sticky because of an unnatural amino acid called
3,4-dihydroxy-L-phenylalanine, or L-DOPA. Oxygen in seawater oxidizes the
catechol side chain of this amino acid, producing a benzoquinone group. Then
lysines in the protein can attack the benzoquinone, connecting protein chains
and forming a gel that attaches the bivalve to a surface.
Because
catechol groups oxidize quickly, synthetic polymers that mimic the mussel
proteins form a gel within minutes of being exposed to air. Atsushi Takahara, at Kyushu University, and his colleagues wanted
to control the timing of gel formation. So they synthesized an acrylamide
polymer containing catechols protected by o-nitrobenzyl groups to
prevent oxidation. When hit with light, these nitrobenzyl groups cleave
themselves off the catechol groups, allowing the polymer to be oxidized.
The
new polymer set within 30 minutes after exposed to high-intensity visible light
from a mercury-xenon lamp. To test the polymer’s adhesive strength, the team
sandwiched the material between two glass plates, triggered gel formation with
light, and then tried to pull the glass plates apart. The shear strength of the
glue was similar to that of other commercial medical adhesives, such as ones
used to seal cuts (Mater. Sci. Eng. C, DOI: 10.1016/j.msec.2005.03.006).
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