Sulfated chitosan as tear substitute with no antimicrobial activity

► Chitosan, an important material in ophthalmological research, was sulfated (CS). ► The sulfation leads to a viscous material, water soluble in neutral medium. ► CS is adequate as tear substitute, which is needed by up to 30% of world population. ► The antimicrobial activity was not observed and differed from previous study. ► CS must have low molecular weight/low sulfation degree to give antimicrobial effect.