Characteristics of polyion complexes of chitosan with sodium alginate and sodium polyacrylate

With a view to the application of chitosan (CS) for drug delivery formulations, formation of interpolymer complexes of CS with sodium alginate (AL) and sodium polyacrylate (AC) was investigated, employing viscosity measurement, Fourier-transform infrared (FT-IR) spectroscopy and elementary analysis. The effect of the molecular weight of AL or AC on complexation with CS was analyzed by gel-permeation chromatography. The binding ratio of a unit molecule of CS with AL was found to be approximately 1:1. This ratio was relatively constant in media of various pH values. On the other hand, the unit molecular binding ratio of CS with AC was greatly affected by the pH values of the media, showing a change from 1:4 to 1:1.7 with increase in pH values from 3.7 to 4.7. Results obtained from gel-permeation chromatography suggested that the lower molecules of AL bind with CS more selectively on complex formation, although the selectivity was unclear in the case of the CS-AC system. Based on the results of FT-IR spectra and elementary analysis, the binding ratio of each component in the solid complexes was very close to that observed in viscosity measurements.