Comparative investigation of the binding characteristics of poly-l-lysine and chitosan on alginate hydrogel

The binding properties of poly-l-lysine and chitosan to alginate have been evaluated quantitatively and compared. Poly-l-lysine bound to alginate hydrogel more rapidly than chitosan as poly-l-lysine has a smaller molar hydrodynamic volume. In addition, poly-l-lysine showed a much higher binding capacity (6.14:1) for alginate hydrogel beads than chitosan (2.71:1), and a little higher binding stoichiometry (0.58) to sodium alginate molecules in solution than chitosan (0.49). An exothermic heat of alginate-poly-l-lysine complexes formation of 2.02 kJ/mol was detected. For alginate–chitosan complexes, the binding enthalpy has been seen to be −3.49 kJ/mol. The stability of the polyelectrolyte complexes was related to their binding enthalpy. The alginate-poly-l-lysine complexes could be disintegrated and rebuilt. By contrast, chitosan was bound with alginate in a steady state. These results provide fundamental insights regarding the structure and property relationships of macromolecules, and will be helpful in designing and selecting appropriate polymers.