Our results highlight the differences between two closed-chamber TEWL measurement instruments, which are designed based on different measurement principles. This may provide insights to find the best practice to improve the quality, precision and sensitivity of the measurements.

No abstract

The critical TiVi performance parameters evaluated proved stable in relation to expected variations in skin RBC(conc) over time. Calibration by way of a two-point method may reduce differences in sensitivity between instruments to further facilitate inter-laboratory comparison of results.

Multiple phase emulsions are increasingly used as alternatives to simple emulsions in personal care products. One of the major advantages of these emulsions over simple emulsions is slow and controlled release of their ingredients. Other favorite cosmetic characteristics of multiple emulsions include occlusivity (in O/W/O emulsions), esthetics and consumer acceptance. Vitamin C (ascorbic acid) has been widely used in formulations of skin care products. Due to its effects on collagen biosynthesis, it is considered as moisturizing and anti-aging active ingredient. Instability problems such as oxidation susceptibility have made incorporating vitamin C in topical formulations a challenging issue. The O/W/O emulsions have been formulated using two-step procedure, to investigate vitamin C stability and its release profile. By using different surfactant types and ratios, volume ratio of phases, multiple emulsions containing vitamin C were prepared. Different parameters and formulation factors such as temperature of phases, duration and speed of mixing were evaluated. Based on our results, more stable emulsions were prepared from non-ionic siliconized surfactants, sorbitan derivatives and co-surfactants such as polyglyceryl derivatives. Physical stability was determined by microscopic examination, centrifugation and incubating emulsions in different temperatures. Vitamin C in vitro release studies from O/W and O/W/O emulsions were conducted using Franz diffusion cell (at room temperature) and UV spectrophotometry. The results showed that in the first four-hour period, about 14% of vitamin C released from O/W/O emulsions. It appears that in multiple emulsions the profile of release follows zero-order kinetics. Our data indicate that incorporating vitamin C in multiple emulsions significantly increased its stability possibly attributed to the formation of reverse micelles of surfactants (and/or co-surfactants), which entrapped vitamin C inside the micelles surrounded by hydrophilic heads of surfactant. Moreover, vitamin C was released from multiple emulsions in a zero order slow and controlled release manner.

Establishment of healthy skin RBC(conc) reference values is important for the design of versatile test procedures for assessment of skin damage caused by vibration tools, chemical exposure or peripheral vascular disease.