title: Alternating bioactivity of polymeric layer-by-layer assemblies: anticoagulation vs procoagulation of human blood.
abstract: The layer-by-layer assembly between cationic chitosan and anionic dextran sulfate was analyzed quantitatively by a quartz crystal microbalance technique in the absence and presence of 0.2, 0.5, and 1 M NaCl in the polymer solution. The apparent film thickness increased upon increasing the NaCl concentration. The anti- versus procoagulant activity of these films against whole human blood was studied by the immersion of a substrate into blood for 30 min incubation time at 37 degrees C. The substrate was coated with films of varying NaCl concentrations and assembly step numbers. There was a critical concentration for the alternating activity; above a concentration of 0.5 M NaCl, both anti- and procoagulation could be observed on the dextran sulfate and chitosan surfaces, respectively. The underlying layer of the assembly was necessary for this alternating activity; after a five-step assembly, the activity was realized. The adsorption of a cationic dye (methylene blue) onto the films revealed that the anionic-charge density derived from dextran sulfate on the film surface was linearly increased with increased NaCl concentration. There was a critical charge density of the dextran sulfate for the anticoagulant activity. An assembly was also constructed from a combination of chitosan and heparin, but the activity was different from that of the former system; strong anticoagulant activity was observed even on the chitosan surface. We suggest that the polymer species and/or the assembly conditions are key factors for realizing the alternating bioactivities of films prepared by the layer-by-layer assembly.
authors.affiliation: Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Serizawa
authors.forename: Miyuki
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Akashi
mesh_terms: D001777:Blood Coagulation; D002686:Chitin / Q000031:analogs & derivatives*; D048271:Chitosan; D020099:Coated Materials, Biocompatible / Q000737:chemistry* / Q000494:pharmacology; D016264:Dextran Sulfate; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D011108:Polymers / Q000737:chemistry* / Q000494:pharmacology; D012965:Sodium Chloride; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D020099:Coated Materials, Biocompatible; D011108:Polymers; D002686:Chitin; D012965:Sodium Chloride; D006493:Heparin; D048271:Chitosan; D016264:Dextran Sulfate