Comparative evaluation of interpolyelectrolyte complexes of chitosan with Eudragit® L100 and Eudragit® L100-55 as potential carriers for oral controlled drug delivery

With a view to the application in oral controlled drug delivery systems, the formation of interpolyelectrolyte complexes (IPEC) between chitosan (CS) and Eudragit® L100 (L100) or Eudragit® L100-55 (L100-55) was investigated at pH 6.0, using elementary analysis. The interaction or binding ratio of a unit molecule of CS with Eudragit® L copolymers depends on the molecular weight of CS, and changes from 1:0.85 to 1:1.22 (1.17 < φ < 0.82) for L100 and from 1:1.69 to 1:1.26 (0.60 < φ < 0.79) for L100-55, respectively. Based on the results of FT-IR, the structure of the IPECs can change substantially as a function of pH (from 5.8 till 7.4). Swelling behavior of physical mixtures (PM) is definitely different, and potential interactions between the two polyelectrolytes were not observed. The release of the model drug diclofenac sodium (DS) was significantly delayed from tablets made up of the IPEC and can be modified by two ways: choosing Eudragit® L copolymer types and/or changing the molecular weight of CS in the IPECs composition.