[soulofA1]

      Hi I am new to here. I know the question I am going to ask may sound like mission impossible, but I hope my question doesn't sound strange. I have to attach a 45 microns diameter carboxylate polystyrene microsphere to a silica fiber with diameter 5-10 microns.

      I have tried many methods but so far no success. I've try to coat the fiber with poly-L-lysine solution like many literature suggested and attach the microspheres on it but they come off after washing with PBS buffer. I've try to coat both with polyelectrolytes of opposite charges but they don't stick.

       My last attempt is to coat the silica fiber with 3-aminopropyltriethoxysilane (APTES), then use EDC/NHS to activate the carboxyl group on the microspheres and couple them on the fiber. On my trial, this method works on glass slide and thick silica fiber (125 micron), but it doesn't give me any microsphere on 5 micron silica fiber. I even try to forcibly transfer the microsphere to the silica fiber using ethanol and isopropyl alcohol but it comes off after the alcohols are dried
      Now I am really out of tricks. Can anybody who has previous experience on carboxylate polystyrene microsphere and silica coupling give me some suggestions? Thank you very much in advance!!