The chemotactic effect of chitosan on PMNs. Freshly isolated polymorphonuclear neutrophils (PMNs) were pre-stained with 1 μg/ml calcein-AM and seeded on a polycarbonate filter placed above a well containing (a) N-formyl-methionyl-leucyl-phenylalanine (fMLP; positive control) or (b) 80% deacetylated (80 M; black line) or 95% deacetylated (95 M; gray line) chitosan. PMNs were allowed to migrate for 1 hour before assessing migration, as described in 'Materials and Methods'. Percentage migration of PMNs = the fluorescence of migrated PMNs/fluorescence of 20,000 PMNs/ml × 100, obtained from the standard curve. Results are presented as mean ± standard error. P values from Student's two-tailed unpaired t-test: *P = 0.01, fluorescence of PMNs migrated toward 25 μg/ml 80 M chitosan versus fluorescence of PMNs migrated toward RPMI (Ctrl-); **P = 0.004, fluorescence of PMNs migrated toward 50 μg/ml 80 M chitosan versus fluorescence of PMNs migrated toward RPMI. The positive control is the fMLP curve. This figure represents the results of three independent experiments.