In my experience, chitosan precipitates at pHs above 6.8. For nanoparticles production, I use to adjust the pH at 5 in order to have a final solution close to 6 and avoid precipitation. If it is just a chitosan solution, the precipitation can be reversed just lowering the pH, however, if the solution contains chitosan-based particles, they will be altered.

I cannot suggest a solution for you to reach a neutral pH solution, unfortunately.

Dear Martin,

Thank you very much for your response. Correctly pointed, even I had precipitation issue. Unfortunately, the particles on which I want to put this chitosan coating on are acid-sensitive. Even at pH 6 within half an hour (assuming shortest coating time) they will eventually undergo significant degradation. Can you think a way, I can prevent this potential degradation ?

Thanks again !

Hello Nadim.

I'm not an expert at all in nanoparticles nor chitosan, just produced some using ionic gelation technique.

With that said, I would try to do like a pH screening in order to find the closest pH as possible to 7 without precipitation and try to coat your particles with this chitosan solution at different ambient temperatures (it might decelerate the degradation and the pH value is correlate with the temperature as well.)

I wish I could help more though.