title: Synergistic effects in semidilute mixed solutions of alginate and lactose-modified chitosan (chitlac).
abstract: The present study specifically aimed at preparing and characterizing semidilute binary polymer mixtures of alginate and chitlac which might find an application in the field of cell encapsulation. A polyanion, alginate, and a polycation, a lactose-modified chitosan, were mixed under physiological conditions (pH 7.4 and NaCl 0.15) and at a semidilute concentration avoiding associative phase separation. The mutual solubility was found to be dependent on the charge screening effect of the added NaCl salt, being prevented below 0.05 M NaCl. A comparison with the behavior of the polyanion (alginate) under the same experimental conditions revealed that both the viscosity and the relaxation times of the binary polymer solutions are strongly affected by the presence of the polycation. In particular, the occurrence of electrostatic interactions between the two oppositely charged polysaccharides led to a synergistic effect on the zero-shear viscosity of the solution, which showed a 4.2-fold increase with respect to that of the main component of the solution, i.e., alginate. Moreover, the relaxation time, calculated as the reciprocal of the critical share rate, markedly increased upon reducing the alginate fraction in the binary polysaccharide solution. However, the formation of the soluble complexes and the synergistic effect are reduced upon increasing the concentration of the 1:1 electrolyte. By containing a gel-forming polyanion (alginate, e.g., with Ca(2+) ions) and a bioactive polycation (chitlac, bearing a beta-linked D-galactose), the present system can be regarded as a first step toward the development of biologically active scaffold from polysaccharide mixtures.
authors.affiliation: Department of Biochemistry, Biophysics and Macromolecular Chemistry, University of Trieste, Via Licio Giorgieri 1, I-34127 Trieste, Italy. idonati@units.it
authors.forename: Ivan
authors.initials: I
authors.lastname: Donati
authors.forename: Ingvild J
authors.initials: IJ
authors.lastname: Haug
authors.forename: Tommaso
authors.initials: T
authors.lastname: Scarpa
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Borgogna
authors.forename: Kurt I
authors.initials: KI
authors.lastname: Draget
authors.forename: Gudmund
authors.initials: G
authors.lastname: Skjåk-Braek
authors.forename: Sergio
authors.initials: S
authors.lastname: Paoletti
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007785:Lactose / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D011073:Polyamines; D000071228:Polyelectrolytes; D011108:Polymers / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry; D012212:Rheology; D012965:Sodium Chloride / Q000737:chemistry; D055672:Static Electricity; D014783:Viscosity
chemical_list: D000464:Alginates; D002118:Calcium; D048271:Chitosan; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D007785:Lactose; D046911:Macromolecular Substances; D011073:Polyamines; D000071228:Polyelectrolytes; D011108:Polymers; D011134:Polysaccharides; D012965:Sodium Chloride