Tailoring doxorubicin sustainable release from biopolymeric smart matrix using congo red as molecular helper

Doxorubicin (Dox) was co-encapsulated with congo red (CR) in order to increase drug encapsulation and sustain the release from gel microbeads composed of alginate-carboxy methyl guar gum (68/32) for oral controlled delivery. No release of either cargo molecule from the microbeads at pH 1.2 within 90 minutes was detected. However, 62% CR and 16% Dox were released from the gels at pH 7.4 at 37 °C in 8 hours when both the cargo molecules were studied alone. Presence of CR in the formulation reduces the release of Dox by about 25-30% under the same experimental conditions. Rheological properties of the formulations have been investigated at different temperatures between 20 and 37 °C. Shear thinning behavior was observed by steady-shear flow experiments for all formulations, and no yield stress was observed for any of the formulations. The temperature effect on Alg-CMGG-Dox-CR evidenced a synergic action between Dox and CR. Dynamic frequency sweep tests were performed to study the viscoelastic properties of the formulations. The patterns observed for Alg-CMGG indicated physical gel characteristics; however, all other formulations showed behaviour typical of concentrated solutions. These results confirm the interaction of Dox and CR, and the concomitant positive effect on sustainable release in oral delivery.