Shelf-Life Studies of Cosmetic Formulations
In one study, resveratrol-containing liposomes and niosomes were formulated in a project designed to create a skin-permeable cream with the intent of generating a percutaneous absorption of the antioxidant.1
Surfactants such as soy phosphatidylcholine (P90), Peceol, and Plurol oleic CC (PLU), along with other materials, were used as well as non-toxic, biodegradable excipients known to be skin penetration enhancers for various other formulations. The liposome and niosome formulations were then analyzed on the TURBISCAN to ensure the stability prediction of the formulation before skin testing. It was shown that, though not visible to the naked eye, only minimal amounts of phase migration in the forms of creaming and clarification were seen and no significant particle flocculation was observed. Any of the minor destabilizations that were observed were also seen to be reversible and not a result of any permanent phenomenon thereby ensuring that simple methods of redispersion (e.g., shaking) can render the material homogeneous and the efficacy of formulation maintained. While the results of the study showed that minimal resveratrol was absorbed into the skin, further and more advanced testing can be done as such liposome-derived mixtures were proven to be stable over time.
It was also shown that vitamin K1-loaded nanocapsules when formulated into a topical cream, delivered more of the fat-soluble vitamin than a control emulsion containing the vitamin.2 The approximate 200 nm nanocapsules can be characterized by the TURBISCAN to show the minimal creaming and flocculation that occurs in the sample, again rendering the formulation stable and viable, and providing information into a brief study in cosmetic formulation shelf-life testing.
Additionally, another study has demonstrated the efficacy of formulations made with vitamin E-infused lecithin and hyaluronic acid nanoparticles3 which are used for the treatment of skin damage and wound healing efforts. It follows that formulations of a wide variety of designs containing an array of different materials can be predictively evaluated using this Static Multiple Light Scattering method.
In yet another study, two particle populations were studied for agglomeration effects using the TURBISCAN. CeO2 and TiO2-engineered nanoparticles are likely to have attractive behavior, resulting in the ability to form large agglomerates over time, and then result in particle migration (sediment) as well as reduction of the surface area of the particles. When this occurs the effectiveness of the sunscreen formulation is thereby foreseeably diminished, and the expiration date of the product is reduced.4 The formulations were then dosed with NaCl, humic acid, and a combination of the two to test the effects of salinity as well as particle surface modification. The TURBISCAN and the TURBISCAN Stability Index (TSI), a one-click comprehensive stability prediction ranking system, were used to measure and quantify the hetero-aggregation of the nanoparticle mixture. Different ratios of the nanoparticles and water sources were tested to provide a clear picture that the flocculation of the particles is minimized by increasing CeO2/TiO2 ratios and the water source had no significant effect on the destabilization phenomena thereby identifying some inconsistencies with previous reports that indicate such water variables are significant. This accelerated, easy approach provides rapid and accurate data on these viscous, concentrated emulsions unmatched by any other current technique.
In summary, the TURBISCAN stability analyzer provides a unique and powerful solution in the field of physical stability analysis and prediction of cosmetic emulsions. Hundreds of peer-reviewed articles and published patents covering the use of the TURBISCAN have utilized the device in the research and development phase of an emulsion fabrication. Phenomena such as phase separation and aggregation kinetics provide high-resolution, real-time data for otherwise undetectable kinetics, even on highly concentrated and viscous samples. The quantitative data provides the formulator with critical information throughout the process and allows for the elimination of guesswork and subjective results and interpretations.
