You may consider some other materials as a possible substitutes to chitosan - aminated cellulose, starch, alginates, collagen, gelatin, chitin etc.
Also, I consider you to cooperate with Iryna S. Kolesnyk on that point.
Here are some important links:
Article Chitosan, the one and only? Aminated cellulose as innovative...
Article Smart nanocomposites of chitosan/alginate nanoparticles load...
https://doi.org/10.1002/nano.202100107
If you have found current answer as useful, please, do not hesitate to recommend it. That will help other researches to find the best answer, according to their purposes. Best of luck in your research!
You can use Cellulose Nanofiber (CNF) or Cellulose Nanocrystal (CNC) are natural polymer that have similar character with chitosan. The hydroxyl group (OH) of CNF and CNC are modifable to get more applicable for wide drug delivery