SPAN 40/TWEEN 80-BASED SOYBEAN OLEOGELS: MODELING OF GELATION KINETICS AND DRUG RELEASE

Background: Oleogel is a thermo-reversible, viscoelastic, semi-solid self-assembled preparation in which an apolar phase gets immobilized within a 3-D networked structure formed via physical or chemical interaction with different organogelators. Objective: The objective of the present investigation was to develop drug-loaded (paracetamol) Span 40 / Tween 80-based soybean oleogels for topical application and to establish a relationship between viscosity, flexibility, thermal stability and drug release of the oleogels by modeling of gelation and release kinetics. Method: Span 40(gelator)/Tween 80(surfactant)-based soybean oleogel formulations were prepared and subjected to organoleptic evaluation, FTIR spectroscopy, thermal analysis, viscosity study, kinetic modeling of gelation and drug release. Results: Tween 80 reduced critical gelator concentration (CGC) of Span 40-based oleogels and also enhanced their thermal stability and viscosity. Gelation time was lowered with the increase in concentration of span, but surfactant addition increased the gelation time. Gompertz model was employed on gelation kinetics data for determination of oil parameter (α) and organogelator parameter (β) which were found to be linked to gel flexibility and thermal stability respectively. At lower organogelator/surfactant concentration (16 and 18% w/v), oleogels are assumed to form flexible, less viscous and thermally stable matrix-type oleogel with better drug release. However, at higher organogelator/surfactant concentration (20% w/v), the nearly ideal zero-order release was achieved in contrast to drug release following  Korsmeyer-Peppas kinetics from oleogel containing only 20% span. Conclusion: Tween 80 is thus assumed to impart higher thermal stability to Span 40 based oleogels probably owing to modification in the microstructure of oleogels.