Development of a Mouthwash Using Freeze-Drying Technique: An Optimization Study

In recent years, the development of solid cosmetics, as part of sustainable cosmetics strategy, is generating increasing interest. In addition, novel approaches such as Quality by Design concept allowed the development of high-quality products together with a decrease in waste generation. The present study aimed the development of freeze-dried mouthwashes containing Cetraria islandica extract using the Quality by Design approach. Based on the results of preliminary experiments, a factorial design with three factors that varied on two levels was developed. As factors, the filler type (sorbitol or mannitol) was chosen as the qualitative factor and the two quantitative factors were: the filler ratio set from 3 to 5% and polymer (methylcellulose) ratio from 0 to 0.5%. After the preparation and the complete characterization of the formulations generated through the experimental design, the effect of the formulation variables on the lyophilized mouthwashes and the interactions between formulation factors were investigated. Finally, an optimal formulation with appropriate mechanical properties that ensure easy manipulation and no material loss when extracted from the package and fast reconstitution was generated.