High-molecular weight chitosan (H-chitosan) with viscosity 500 mPa s (1%, 20 ◦C) and degree of deacetylation 90%,low-molecular weight chitosan (L-chitosan) with viscosity 150 mPa s (1%, 20 ◦C) and degree of deacetylation 90% were purchased from Qingdao Honghai Biotechnology Company (Shandong, China)