The binding of proteins to an ITO surface can be prevented by coating it with PEG groups (polyethylene glycol). PEG-silane is used to create the coating.

can somebody help with:

  • Why does PEG-silane bind to ITO (indium tin oxide)? and how? (which bond etc.)

  • Why does PEG repel proteins?

  • Are there better coatings to use to repel proteins?

  • $\begingroup$ Could you elaborate what you have found/investigated until now? $\endgroup$
    – Michiel
    May 18 '13 at 15:25

PEG "silane" is $\ce{HOCH2CH2O-PEG-CH2CH2CH2-Si(OCH3)3}$. (Pt-catalyzed $\ce{HSi(OCH3)3}$ addition to the terminal allyl monoether.) A metal oxide surface can be hydrated, (bulk)M-OH. The TMS end hydrolyzes and dehydrates to tetrahedrally covalently bonded $\ce{HOCH2CH20-PEG-0Si(OM#bulk3)}$. The alcohol polyethoxy end hydrated waves in the water, and the protein ignores the PEGylated surface.

An especially fine biocompatibilizer rendering nearly any organic surface except silicone rubber invisible to protein deposition and denaturation is poly(N-vinyl pyrrolidone). It can be linearly radiation grafted into organic surfaces (visualize with Congo Red). Plexiglass gives a 19 degree average contact angle in saline and implants with neither cellular or humoral reaction. NVP plasma deposition gives you sludge. There is no obvious (inexpensive) chemical attachment of its low polymer or oligomer to a surface. Pity.


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