Interpolyelectrolyte complexes based on Carbopol and oppositely charged polymer as new carriers for oral controlled diclofenac delivery

Carbopol polymers are polymers of acrylic acid and crosslinking agents; there is the prospect of penetration of linear macromolecules between the mesh size of crosslinked Carbopol microgels for a certain period of time. Interpolyelectrolyte complex (IPEC) samples between Carbopol and linear polycations (Eudragit EPO-EPO) were obtained at different interpolyelectrolyte reaction (IPER) times (1, 3, and 7 days). Confirmation of the IPEC structures was proved by FTIR and mDSC. Moreover, according to the results of elemental analysis and mDSC, an increase in the duration of IPER time did not lead to a significant increase in the fraction of the incorporated EPO (CS), since its amount in polycomplex samples remains almost unchanged and the Tgs varies slightly and it depends from the Carbopol grade used. Analysis of the particle size and zeta potential of polycomplex gels showed that the obtained IPEC samples are nanosized, and the particle charge depends on the presence of free ionized carboxyl groups Carbopol (Noveon) or positively charged dimethylamino groups of EPO on their surfaces. After increasing the duration of IPER up to 3 days, a decrease in zeta potential values was observed. In the case of 7 days, an increase in particle size was observed due to their aggregation (C2020/EPO, C10/EPO, NAA-1/EPO). Mathematical modeling of diclofenac sodium release according to the Korsmeyer-Peppas equation showed that all IPEC samples were characterized by the Super Case-II transport mechanism, except for C10/EPO sample, which was characterized by Anomalous transport.