You can try Wet impregnation method

have you tried sonication ?

The molecular weight of chitosan plays an important role in chitosan nanoparticle formation through ionic complexing. First, try to use low molecular weight chitosan. Second, under vigorous stirring chitosan solution, add the crosslinker (TPP) solution dropwise into chitosan solution. Finally, let the solution to stir for at least 30 min for hardening the nanoparticles.

Hi mokthar working with chitosan is a tricky one. As chitosan is from natural source so we cant get the same quality of chitosan everytime. Please makesure you check the following while you work on chitosan

1)deacetylation  percentage  and mol.wt of chitosan

2)I suggest to dissolve in 1%acetic acid  atleast 2 hrs before starting the experiment.

3) maintain ph of chitosan around 5

4) temperature of chitosan solution is a key factor as it controls the chain length and  viscosity. I maintained chitosan solution at 60oc and i got same results evrytime.

Thanks to all