Dear John, 

there are a lot o reactions reported, you can couple thiol containing species with polymer in very small ratio, say 1%, 2% etc. Its pure organic chemistry, I'm attaching one of the best paper, designing of mercapto ligands for nanoparticles. please find the attached link. 

Good luck

http://pubs.acs.org/doi/full/10.1021/la062623h

This is really not a good idea, carboxylate groups bind to gold nanoparticles through weak electrostatic interactions. If you can introduce some thiol (-SH) moities in polymer this will provide very strong stabilization. And which part you are planing to conjugate by  EDC/ NHS coupling if you want to consume the carboxylate groups via stabilization ? 

Thanks Muhammad.

I am planning to use the EDC/ NHS coupling system to conjugate the polyamic acid to antibodies for biosensor applications. However, I also want the polyamic acid to be immobilized onto gold nanoparticles which leads me to my dilemma about carboxylate vs thiol groups for  AuNPs  conjugation. 

How can I introduce functional thiol groups to polyamic acids? are there some suggestions?

Thanks.

i think for this kind of attachments and bonding between functional groups we can use  coupling agents such as DCC/ DMAP or EDC/NHS in a controlled condition. as you know thiol groups have a good ability to gold and you should activate gold nano particles by a double functional molecule that one of them should be thiol for attach to gold surface and another can be OH,COOH or NH2 . anyway you should attach the polymer to activated gold nanoparticles.

Dear John, 

there are a lot o reactions reported, you can couple thiol containing species with polymer in very small ratio, say 1%, 2% etc. Its pure organic chemistry, I'm attaching one of the best paper, designing of mercapto ligands for nanoparticles. please find the attached link. 

Good luck

http://pubs.acs.org/doi/full/10.1021/la062623h

Thanks for your insights Kamran.

Muhammad, 

I am grateful for your time and also for the paper. Will have a keen look at it then will give you some feedback.

Thanks a lot.