title: Sulfated chitosan as tear substitute with no antimicrobial activity.
abstract: Chitosan of high molar mass and with 82% deacetylation was sulfated using two procedures and characterized. In the first method sample chitosan-S1 was produced using chlorosulfonic acid as the sulfating agent and N,N-dimethylformamide as the medium, and in the second method (chitosan-S2) formic acid was also used. The degrees of sulfation were 0.87 (chitosan-S1) and 0.67 (chitosan-S2). FTIR spectra showed bands at 1230, 800 and 580 cm(-1), attributed to sulfation. Moisture content followed the order: chitosan-S-0.87>chitosan-S-0.67>chitosan. Chain depolymerization was verified by GPC. Aqueous solutions showed pseudoplastic behavior and the viscosity at a concentration of 0.3% (w/v) was higher than that of healthy human tears (close to 3 mPas at shear rate 130 s(-1)). Substitutions in the C2NH and in C6OH groups were verified by NMR. Antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa was not observed. Considering that chitosan-S-0.67 had a higher solubility, less chain depolymerization, higher yield and better thermal stability in comparison with chitosan-S-0.87, the derivative with DS 0.67 offered the greatest potential for use in formulations of tear substitutes.
authors.affiliation: Department of Organic and Inorganic Chemistry, Federal University of Ceara, CP 6.021, CEP 60455-760, Fortaleza, Ceará, Brazil.
authors.forename: Natália R
authors.initials: NR
authors.lastname: Pires
authors.forename: Pablyana L R
authors.initials: PL
authors.lastname: Cunha
authors.forename: Jeanny S
authors.initials: JS
authors.lastname: Maciel
authors.forename: Alysson L
authors.initials: AL
authors.lastname: Angelim
authors.forename: Vania M M
authors.initials: VM
authors.lastname: Melo
authors.forename: Regina C M
authors.initials: RC
authors.lastname: de Paula
authors.forename: Judith P A
authors.initials: JP
authors.lastname: Feitosa
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D048271:Chitosan / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D009883:Ophthalmic Solutions / Q000737:chemistry* / Q000494:pharmacology*; D009994:Osmolar Concentration; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D012212:Rheology; D013211:Staphylococcus aureus / Q000187:drug effects; D013431:Sulfates / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D009883:Ophthalmic Solutions; D013431:Sulfates; D048271:Chitosan