MRS Fall 2009: Wednesday morning
I've been to a half-dozen talks this morning in SS & Y (in the single letters!), but I wanted to focus on my favourite.
SS6.1 "Bioinspired immobilization chemistries for surface modification & biointerfacial control" Phillip Messersmith (Northwestern)
I've been following the work from the group of Northwestern's Phillip Messersmith since they published information about their "geckle" adhesive in Nature a couple years ago. The name comes from a combination of gecko, the animal that can walk on walls with this spatula-tipped setae, and mussel, an animal that secretes threads rich in hydroxylated tyrosine (DOPA) that can stick fast to many (all?) inorganic and organic surfaces even when they're wet. He's an engaging speaker...
As you might expect, the talk began with an introduction on the mussel proteins. The proteins from Mytilus edulis are rich in tyrosine, lysine and histidine. Mefp5 has the highest concentration of these, with 27% DOPA (that is, hydroxylated tyrosine). More than half of the residues are Tyr and Lys.
So how does it work? The DOPA is oxidised to a quinone, particularly at high pHs (it's a 2H+/2 e– reaction, so having fewer protons around means that the equilibrium is shifted to the quinone). This then can form cross links with both organics (including the side chains on Lys, Cys and His) and inorganics (such as the surface of a rock) by forming a metal-topped, five-membered, two-oxygen-containing heterocycle attached to the phenyl ring. My organic chemistry is failing a bit to remember the name of the parent structure. They did some nice work, including a lot of AFM adhesion-force measurements, to work out the mechanism of the adhesion and that the quinone form was much "stickier" than the catechol form.
They're taking this further to create "mussel-inspired" adhesives. These consist of a 10 kDa, four-armed PEG terminated with catechols. This reacts with an oxidising agent (e.g., NaIO4) to start off the cross-linking process. This can be delivered from a two-plunger syringe and sets in under a minute. He showed a couple examples involving islet transplantation & fetal wound sealing. There was a also a second demonstration of these "bioinspired" materials with a polyDOPA coating that could then be secondarily functionalised with proteolysis-resistant, anti-biofouling peptoids, that have their side chains on the amide nitrogen instead of the alpha carbon.
SS6.1 "Bioinspired immobilization chemistries for surface modification & biointerfacial control" Phillip Messersmith (Northwestern)
I've been following the work from the group of Northwestern's Phillip Messersmith since they published information about their "geckle" adhesive in Nature a couple years ago. The name comes from a combination of gecko, the animal that can walk on walls with this spatula-tipped setae, and mussel, an animal that secretes threads rich in hydroxylated tyrosine (DOPA) that can stick fast to many (all?) inorganic and organic surfaces even when they're wet. He's an engaging speaker...
As you might expect, the talk began with an introduction on the mussel proteins. The proteins from Mytilus edulis are rich in tyrosine, lysine and histidine. Mefp5 has the highest concentration of these, with 27% DOPA (that is, hydroxylated tyrosine). More than half of the residues are Tyr and Lys.
So how does it work? The DOPA is oxidised to a quinone, particularly at high pHs (it's a 2H+/2 e– reaction, so having fewer protons around means that the equilibrium is shifted to the quinone). This then can form cross links with both organics (including the side chains on Lys, Cys and His) and inorganics (such as the surface of a rock) by forming a metal-topped, five-membered, two-oxygen-containing heterocycle attached to the phenyl ring. My organic chemistry is failing a bit to remember the name of the parent structure. They did some nice work, including a lot of AFM adhesion-force measurements, to work out the mechanism of the adhesion and that the quinone form was much "stickier" than the catechol form.
They're taking this further to create "mussel-inspired" adhesives. These consist of a 10 kDa, four-armed PEG terminated with catechols. This reacts with an oxidising agent (e.g., NaIO4) to start off the cross-linking process. This can be delivered from a two-plunger syringe and sets in under a minute. He showed a couple examples involving islet transplantation & fetal wound sealing. There was a also a second demonstration of these "bioinspired" materials with a polyDOPA coating that could then be secondarily functionalised with proteolysis-resistant, anti-biofouling peptoids, that have their side chains on the amide nitrogen instead of the alpha carbon.
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