Application of Oscillatory rheology in long-term stability studies of minimalist emulsion
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Presented by: Laura Aiello
INTRODUCTION: Structured phase formulations combine the advantages of emulsifying and gelling systems such as the delivery of hydro- or liposoluble actives, pleasant sensorial and emollient. The development of these systems with few ingredients and without the use of surfactants represents a minimalist approach, more sustainable and with less potential for skin irritation. Microstructure characterization through oscillatory rheology provide relevant informations about formulation consistency and long-term physical stability. This study aimed to evaluate long-term stability of emulgels through their macroscopic and rheological properties.
METHODS: Organolepetic (color, odor, homogeneity) analysis were performed. Oscillatory rheological characterization was carried out to evaluate critical analytical atributes: viscosity, viscoelastic behaviour (storage modulus -G’ and loss modulus - G’’) and thermosensitivity. Developed emulgel were analyzed after 24 hours it preparation (T0), after two years stored at room temperature (T2-Room) and stored in oven at 40ºC (T2-Oven). RESULTS: There was no organolepetic alteration in formulation after two years stored under room conditions compared to the initial sample (T0). Emulgel stored at 40ºC presented intensified color and odor. All formulations were characterized by a pseudoplastic behavior. Flow curve showed significantly lower viscosity values to emulgel submitted to thermal stress. Gel-like behavior was observed for the formulations kept under ambient conditions (G'>G''), while the difference in values for the storage and loss modulus was not significant for T2-oven sample. Systems studied showed, in general, a linear themosensitivity behavior.
DISCUSSION AND CONCLUSION: Structured phase formulations have been a strategy used for the stabilization of active delivery systems in a simple way and without the need for the use of primary surfactants.
In long-term, thermal stress conditions accelerated the changing processes of the organolepetic and rheological parameters. Gel-like behavior of formulations T0 and T2-room implies a more stable and stronger microstructure of the gel. The flow properties and viscoelasticity showed that the binding forces of the polymeric chains present in the emulgel are more easily deformed after being subjected to thermal stress conditions (T2-Oven).
METHODS: Organolepetic (color, odor, homogeneity) analysis were performed. Oscillatory rheological characterization was carried out to evaluate critical analytical atributes: viscosity, viscoelastic behaviour (storage modulus -G’ and loss modulus - G’’) and thermosensitivity. Developed emulgel were analyzed after 24 hours it preparation (T0), after two years stored at room temperature (T2-Room) and stored in oven at 40ºC (T2-Oven). RESULTS: There was no organolepetic alteration in formulation after two years stored under room conditions compared to the initial sample (T0). Emulgel stored at 40ºC presented intensified color and odor. All formulations were characterized by a pseudoplastic behavior. Flow curve showed significantly lower viscosity values to emulgel submitted to thermal stress. Gel-like behavior was observed for the formulations kept under ambient conditions (G'>G''), while the difference in values for the storage and loss modulus was not significant for T2-oven sample. Systems studied showed, in general, a linear themosensitivity behavior.
DISCUSSION AND CONCLUSION: Structured phase formulations have been a strategy used for the stabilization of active delivery systems in a simple way and without the need for the use of primary surfactants.
In long-term, thermal stress conditions accelerated the changing processes of the organolepetic and rheological parameters. Gel-like behavior of formulations T0 and T2-room implies a more stable and stronger microstructure of the gel. The flow properties and viscoelasticity showed that the binding forces of the polymeric chains present in the emulgel are more easily deformed after being subjected to thermal stress conditions (T2-Oven).