[Barret]

As I wrote in another post I want to create Chitosan nanoparticles.
My material is Low molecular weight chitosan (about 200.000 da), and stated to be pure.

I ve tried solutions up to 3% wt. in 1% acetic acid. Stirring and 1-2 hours sonication as the supplier suggests.
Still the dissolution is not perfect as the mixture is very viscous and you can see some undissolved particles in it.

The only way I ve managed to decrease the viscosity of the medium is by heating it up to 70 C for a day. The resulting solution is a lot less viscous (almost like water) but its colour has changed from light yellow to dark orange. Could this be a sign of crosslinking?

What is the best way for effective and safe dissolution of chitosan?

Thanks in advance for any answers

[fledarmus]

chitosan is a polysaccharide - if you are heating it with acetic acid, my guess would be that you are breaking the links and going back to a monosaccharide. Crosslinking should either make it more viscous or make the crosslinked molecules separate from the solution.