Formulation and Comparative in vitro Drug Release and Membrane Diffusion of Diclofenac Sodium Cream: Vigna subterranea Starch Based Pickering Versus Emulsifying Wax-Based.

Pickering emulsion stabilized with starch is a promising alternative to conventional surfactant- based topical creams in support of green technology. Limited studies have been done on this research topic. This study compared the in vitro drug release kinetics and membrane diffusion characteristics of topical diclofenac sodium creams formulated as annealed Vigna subterranea starch-based Pickering emulsions and emulsifying wax-based creams. Vigna subterranea starch was extracted, modified to yield annealed starch. The morphology, crystallinity, swelling index, wettability, hydration, and emulsion capacities were evaluated. FTIR spectra of physical mixtures of diclofenac sodium and the excipients revealed no sign of incompatibility. Diclofenac sodium 1% topical oil -in- water creams, F1-F4 were prepared by fusion method, using varying concentrations of annealed starch (1.0, 2.5, 5.0, 7.5 % respectively) as the Pickering stabilizer. F9 and F11 with native Vigna subterranea starch and emulsifying wax respectively in the concentration of 7.5% were formulated for comparison. In vitro drug release was investigated using a cellulose membrane diffusion model in phosphate buffered saline, from where samples were collected at predetermined intervals and analyzed using UV- visible spectrophotometry. Release data was fitted into various kinetic models. Annealing modified the physicochemical properties of Vigna subterranea starch and improved its suitability as a Pickering stabilizer. F1-F11 showed satisfactory physicochemical characteristics. The release profiles showed differences (P<0.05) between the Pickering and conventional cream systems. This indicated the influence of the stabilizing matrix on drug transport. The optimized annealed starch cream F4 exhibited the highest release efficiency (87.94%) and area under release curve (527.5%) with the lowest mean dissolution time (0.67 hr) indicating rapid drug release whereas the emulsifying wax formulation (F11} showed a release efficiency of 77.54% and native starch formulation (F9) showed 52.24%. Higuchi was found to be the best fitting kinetic model, with the highest correlation coefficient (R2 =0.989) while Korsmeyer -Peppas analysis showed Fickian diffusion (n< 0.5) as the release mechanism. These findings demonstrate that annealed Vigna subterranea starch is a promising, sustainable alternative to emulsifying wax for topical diclofenac sodium cream.

Diclofenac sodium, annealed starch, Pickering, emulsifying wax, stabilizer

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