Separation of high molecular weight PDMS from nanoparticles
Posted: Sun Mar 15, 2015 4:31 am
Hello everyone,
I have been recently plagued by a problem that I heard you all might be able to help me with. My research involves the synthesis of high molecular weight polydimethylsiloxane ligands that we attach to the surface of nanocrystals. The nanocrystals come with a native ligands attached that we remove by basically introducing our ligand in ~25 times excess. With other low molecular weight ligands, we would be able to do repeated methanol rinses to remove the excess ligand, leaving us with our nanocrystals with the new ligand, but this method hasn't been working very well for us with this type of ligand. We also tried high speed centrifugation, but I think that our ligand is just too thick for that to work properly. The main culprit here is around 60 kDa, and since our nanocrystal itself is around 20 kDa and would have a lot of these 60 kDa ligands attached, I assume that we would be able to use some size exclusion method to remove the excess ligand. The problem is, I've talked to various vendors and no one seems to have beads even upwards of 20 kDa. Another potential problem here is that the mobile phase would have to be toluene (or hexanes, or chloroform), and these solvents generally aren't too friendly to most beads. I've found a dialysis kit on Sigma's website that is made of cellulose ester, but the MWCO is 100 kDa. Do you guys think that would work?
Thanks a bunch for your help.
I have been recently plagued by a problem that I heard you all might be able to help me with. My research involves the synthesis of high molecular weight polydimethylsiloxane ligands that we attach to the surface of nanocrystals. The nanocrystals come with a native ligands attached that we remove by basically introducing our ligand in ~25 times excess. With other low molecular weight ligands, we would be able to do repeated methanol rinses to remove the excess ligand, leaving us with our nanocrystals with the new ligand, but this method hasn't been working very well for us with this type of ligand. We also tried high speed centrifugation, but I think that our ligand is just too thick for that to work properly. The main culprit here is around 60 kDa, and since our nanocrystal itself is around 20 kDa and would have a lot of these 60 kDa ligands attached, I assume that we would be able to use some size exclusion method to remove the excess ligand. The problem is, I've talked to various vendors and no one seems to have beads even upwards of 20 kDa. Another potential problem here is that the mobile phase would have to be toluene (or hexanes, or chloroform), and these solvents generally aren't too friendly to most beads. I've found a dialysis kit on Sigma's website that is made of cellulose ester, but the MWCO is 100 kDa. Do you guys think that would work?
Thanks a bunch for your help.