Hi Aurore, the chitosan matrix should be stable in most buffers with a pH > 7.

As for your results from the BCA assay, the BCA reagent reacts with amide bonds. Chitosan is derived from chitin, which has acetylated N-linked sugars, e.g. amides.

The process of converting chitin to chitosan is to deacetylate the chitin. This not a perfect process and there will always be some amide groups left that can react with the BCA reagent.

Here is a good review

http://farmacia.udea.edu.co/~marinos/chitin.pdf

Hi Aurore, I don't know the question you asked. Steingrimur Stefansson gave you a good suggestio.

  Wish you everting well

Meiliang LI

Thanks :)