I have a silica microsphere, and I wish to use EDC/NHS to couple a diamine spacer arm, but was told that the hydroxyl group itself wouldn't be reactive enough, so if I convert it to carboxyl, I'm hoping it will work. Will an acetic anhydride accomplish this, or is there some other methodology? Thanks in advance to anyone that takes the time to answer.
Hi Jonas,
Thanksyou,
I shall look into those Silanes, will that be a reflux functionalisation to add those silanes?
FIrst react the glass with APS to introduce the amine group. Then you can react teh amine with Boc-Ahx-OH using EDC. You can repeat the Boc-Ahx copuling several times to increase the size of your linker. In the past I have also used Boc- or Fmoc-PEG-COOH, they provide good spacing and protect surface from non-specific adsorption (importat if you want to use it for biological applciations).
The easiest way is to reflux the vacuum-dried silica in the toluene solution of 3-mercaptopropyltrimethoxysilane for 3-4 h, filter, wash with toluene, dry, treat with aqueous solution of iodoacetic acid basified with NaOH to pH 9 at room temperature overnight. Whether the alkylation of the SH-groups is complete, you can check with NBD-Cl solution in isopropanol basified with Et3N: the solid after washing should not be yellow. Stirrer bars often destroy porous silica particles by grinding them; it is safer to use overhead mixer or a shaker, or even shake the suspension manually from time to time.
How would acetic anhydride do the trick? Wouldn't it just acetylate your silica surface and generate free acetic acid?
Hi Andre, Vikram and Zhiqiang
Thank you for your suggestions.
Andrei, unfortunately that isn't something I can do right now.
Zhiqiang, would you have a protocol for that?
Simplest method is a treatment with 3-(Triethoxysilyl)propyl isocyanate (look at link and some citation therein). After isocyanate functionalization, add excess of diamine in inert solvent (THF is suitable)
http://www.sigmaaldrich.com/catalog/product/aldrich/413364
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