Dear Zahra Falahati

Diluted acids is favorable to dissolve chitosan and to keep its structure  . 

Chitosan can be dissolved in acidic solvents. You can use any of the two methods

Chitosan can be dissolve in the mixture of 0.1M Acetic acid and 0.2M NaCl at Room temp. 12 Hours with stirring

Chitosan can be dissolved in 0.1M acetic acid at 60 degrees celcius 5 hrs with stirring

differ according to chitosan source

Pls. find the attached files and the references, good luck

Hoping this will be helpful to your project

Regards

Prof. Houda Kawas

http://onlinelibrary.wiley.com/doi/10.1002/app.13537/abstract?systemMessage=Pay+Per+View+on+Wiley+Online+Library+will+be+unavailable+on+Saturday+15th+April+from+12%3A00-09%3A00+EDT+for+essential+maintenance.++Apologies+for+the+inconvenience.

http://www.sciencedirect.com/science/article/pii/S0079670009000318

http://www.sciencedirect.com/science/article/pii/S0144861705004571

http://cdn.intechopen.com/pdfs/16199/InTech-Characterization_and_properties_of_chitosan.pdf

dear Prof. Houda Kawas

thanks for your answer. actually I used he first methods that you mentioned but after 12 hour it was not solubilized. I tried to solve 0.05 gram to 10ml  the mixture of 0.1M Acetic acid and 0.2M NaCl at Room temp.

in addition to solving problem, I don't know how I can adjust the pH of solved chitosan to physiologic pH. do ypu have any suggestion?

thanks again

regards

Zahra

Dear Zahra

for better understanding Chitosan

Pls. find the attached files and the references, good luck

Page 173 in: Severian Dumitriu. 2001. Polymeric Biomaterials, Revised and Expanded CRC Press, 2001.Pp.1168. ISBN 0203904672, 9780203904671

https://books.google.com/books?id=iCm1SJBDZwkC&pg=PA173&lpg=PA173&dq=chitosan%2Bphysiologic+pH&source=bl&ots=0_sV9JFoAD&sig=odSoXAVzNqyyeVwEKZ_QiC0l8JQ&hl=ar&sa=X&ved=0ahUKEwiH2fegpabTAhVGCCwKHXp7D9wQ6AEITDAF#v=onepage&q=chitosan%2Bphysiologic%20pH&f=false

page 36 in: Se-Kwon Kim. 2013. Chitin and Chitosan Derivatives: Advances in Drug Discovery and Developments CRC Press, Pp.527. ISBN1466566280, 9781466566286

https://books.google.com/books?id=GIJcAgAAQBAJ&pg=PA36&lpg=PA36&dq=chitosan%2Bphysiologic+pH&source=bl&ots=0fwPrHuWpH&sig=Kj87uAkDPEfe5el7kUiaYOcQor4&hl=ar&sa=X&ved=0ahUKEwiH2fegpabTAhVGCCwKHXp7D9wQ6AEIUDAG#v=onepage&q=chitosan%2Bphysiologic%20pH&f=false

https://en.wikipedia.org/wiki/Chitosan

https://books.google.com/books?id=9XQZVUO1CscC&pg=RA1-PA92&lpg=RA1-PA92&dq=chitosan%2Bphysiologic+pH&source=bl&ots=uFjjbidMZG&sig=gvxdzW34ddIUq41lMq9escAZqjs&hl=ar&sa=X&ved=0ahUKEwiH2fegpabTAhVGCCwKHXp7D9wQ6AEIVDAH#v=onepage&q=chitosan%2Bphysiologic%20pH&f=false

Chanoong Lim; Dong Woog Lee; et al. (2015). "Contact time- and pH-dependent adhesion and cohesion of low molecular weight chitosan coated surfaces". Carbohydrate Polymers. 117 (6): 887–894. doi:10.1016/j.carbpol.2014.10.033

https://books.google.com/books?id=oa8YpRsD1kkC&pg=RA1-PA226&lpg=RA1-PA226&dq=chitosan%2Bphysiologic+pH&source=bl&ots=lc48XmeHhk&sig=9ftyfsCsY_hdllkT22vqDrwC6h4&hl=ar&sa=X&ved=0ahUKEwiH2fegpabTAhVGCCwKHXp7D9wQ6AEIWDAI#v=onepage&q=chitosan%2Bphysiologic%20pH&f=false

https://books.google.com/books?id=virvCAAAQBAJ&pg=PA42&lpg=PA42&dq=chitosan%2Bphysiologic+pH&source=bl&ots=Gwysl0Luhf&sig=ZRy1a8I7LD-CTlwriv5L_G6VMEY&hl=ar&sa=X&ved=0ahUKEwiH2fegpabTAhVGCCwKHXp7D9wQ6AEIXDAJ#v=onepage&q=chitosan%2Bphysiologic%20pH&f=false

https://books.google.com/books?id=iCm1SJBDZwkC&pg=PA173&lpg=PA173&dq=chitosan%2Bphysiologic+pH&source=bl&ots=0_sV9JFoAD&sig=odSoXAVzNqyyeVwEKZ_QiC0l8JQ&hl=ar&sa=X&ved=0ahUKEwiH2fegpabTAhVGCCwKHXp7D9wQ6AEITDAF#v=onepage&q=chitosan%20physiologic%20pH&f=false

http://www.groupes.polymtl.ca/tissue/Publications/PDFs/MB43.pdf

https://books.google.com/books?id=g6gyGN0mRiAC&pg=PA536&lpg=PA536&dq=solved+chitosan+to+physiologic+pH&source=bl&ots=mphfS2Ou6P&sig=BknWh2IbrkSlFAzosD9JWACCkXY&hl=ar&sa=X&ved=0ahUKEwjis-rKo6bTAhUFEiwKHfmOBJ8Q6AEIWDAH#v=onepage&q=solved%20chitosan%20to%20physiologic%20pH&f=false

https://books.google.com/books?id=OlPRBQAAQBAJ&pg=PA266&lpg=PA266&dq=solved+chitosan+to+physiologic+pH&source=bl&ots=E8iBCZIQab&sig=xu7zjKC8ZCOC3OETHAj3HKVNRUg&hl=ar&sa=X&ved=0ahUKEwjis-rKo6bTAhUFEiwKHfmOBJ8Q6AEISDAF#v=onepage&q=solved%20chitosan%20to%20physiologic%20pH&f=false

page 629 in: Matthias Giese. 2013.Molecular Vaccines: From Prophylaxis to Therapy Springer Science & Business Media, Pp.870. ISBN3319009788, 9783319009780

https://books.google.com/books?id=Oda4BAAAQBAJ&dq=solved+chitosan+to+physiologic+pH&hl=ar&source=gbs_navlinks_s

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3651799/

https://books.google.com/books?id=NFR7DQAAQBAJ&pg=PA97&lpg=PA97&dq=solved+chitosan+to+physiologic+pH&source=bl&ots=J2kZnFnSSV&sig=R2Mp3fWvpHFWXp1uWMKdT1bYSHE&hl=ar&sa=X&ved=0ahUKEwjis-rKo6bTAhUFEiwKHfmOBJ8Q6AEINTAC#v=onepage&q=solved%20chitosan%20to%20physiologic%20pH&f=false

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920537/

https://www.google.ch/patents/CA2704162A1?cl=en

http://pubs.rsc.org/en/content/articlelanding/2010/jm/b916528b#!divAbstract

http://www.groupes.polymtl.ca/tissue/Publications/PDFs/MB92.pdf

https://www.ncbi.nlm.nih.gov/pubmed/22480314

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4431508/

https://www.ncbi.nlm.nih.gov/pubmed/17096545

https://www.ncbi.nlm.nih.gov/pubmed/26056441

http://pubs.acs.org/doi/abs/10.1021/acsami.5b00851

http://www.sciencedirect.com/science/article/pii/S0142961298000362

Hoping this will be helpful to your project

Regards

Prof. Houda Kawas

Also