When centrifuged the first time all GNP conjugate settles down with no problem but after removal of supernatant, addition of PBS pH 7.4 and centrifuging the second time, most of the gold nanoparticles get stuck on the side wall irreversibly. Big aggregates can even be seen at the bottom. Any suggestions?
Hi,
this is probably because of pH and particle charge (mostly due to protein overall charge). You can try to use lo-bind eppendorf centrifuge tubes. They have a polymer thin film on and don't allow for NPs to stick!
Hi, Can you please tell me the protocol used for protein A gold conjugation.
You could try to use Teflon tubes for centrifugation instead of polymeric tubes. This will also avoid leakage of polymers from the tube and into your solution. When you add PBS (as Svetlana rightly argues), you will collapse the electrical double layer surrounding the GNPs and they will thus be more prone to aggregation- needles if you centrifuge them or not.
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