Modulation of surface tension and rheological behavior of methyl cellulose – Amino acid based surfactant mixture by hydrophobic drug rifampicin: An insight into drug stabilization and pH-responsive release

Abstract

The interaction of Methyl Cellulose (MC) with amino acid-based anionic surfactants viz. sodium lauryl sarcosinate (SLS) and sodium stearyl sarcosinate (SSS) having different hydrophobic chain lengths but the same head group has been investigated using surface tension, rheological and UV–Vis spectrophotometric measurements. The effect of poorly water-soluble drug Rifampicin (Rif) on the physicochemical and rheological properties of the MC-surfactant system was also elucidated. The tensiometric profiles of the two systems (MC + SLS & MC + SSS) indicated that the Critical Aggregation Concentrations (CACs) are further reduced in presence of Rif while as the Critical Micelle Concentrations (CMCs) remain more or less constant. The oscillatory rheological experiments revealed that the gelation is highly dependent upon the applied frequency and concentration of the surfactants. Moreover, the viscoelasticity of the polymer-surfactant system is greatly modulated by the presence of Rif molecules which tend to decrease the viscoelasticity of the MC + SSS system more than that of MC + SLS system till the CAC. The kinetic stability of Rif w.r.t. oxidation with H2O2 in MC and MC-surfactant systems revealed that the polymer-surfactant systems were able to stabilize and protect the drug more than individual polymer or surfactant systems. The systems were also investigated for drug (Rif) release at pHs 7.4 and 4.0 in which diffusion predominant release was observed at pH 7.4 while at pH 4.0, the release was controlled by both diffusion and relaxation phenomenon. These experimental findings could be important for modulating the use of polymer-surfactant systems for enhancing the drug stability and their application in pH-responsive drug release.