40 SKIN CARE
■ 4. IPMP was extracted into ethanol by 4-fold dilution with ethanol. ■ 5. IPMP release was measured by GC analysis.
Evaluation results The results of the IPMP release rate measured at each stirring time are shown in Figure 3. While the release of IPMP in the gel lotion blended with IPMP alone saturated in about three hours after mixing with squalane, the lotion to which IPMP-loaded spherical silica aerogel powder was added gradually released IPMP, and saturated after nine hours. This is thought to be due to the fact that IPMP
is loaded inside the pores of the spherical silica aerogel powder, which reduces the amount of IPMP exposed to the outside and at the same time increases the flow resistance, resulting in the suppression of IPMP release and the gradual release of IPMP. In other words, this result confirms the
sustained release effect of IPMP by loading it into spherical silica aerogel powder, and the formulation of spherical silica aerogel powder in the gel lotion was found to be effective.
Conclusion Tokuyama Corporation has commercialized spherical silica aerogel powder called “Airlica” for cosmetics applications. Since the spherical silica aerogel powder has a very high porosity, we investigated whether a sustained release effect could be obtained by loading an active ingredient into the pores of the powder. Isopropyl methylphenol (IPMP) was used as the active ingredient, and since IPMP is a fat-soluble crystal, it was dissolved in ethylhexyl palmitate, an oil commonly used in cosmetics, and this solution was loaded onto the spherical silica aerogel powder.
100 90 80 70 60 50 40 30 20 10 0
0 5 Figure 3: IPMP release in gel lotion PERSONAL CARE June 2024 10 15 Elapsed time (h) 20 25 The lotion containing the IPMP-loaded
spherical silica aerogel powder (IPMP concentration 0.1 wt%) was prepared. This lotion was applied to the human face, and the sustained release effect was evaluated by observing the rate of increase of acne bacteria after application. The acne bacteria were observed by measuring the amount of porphyrin in the skin before and after application of the lotion using the VISIA Evolution skin image analyzer. Porphyrin is a metabolite of Bacillus/
Cutibacterium acnes, the main pathogen of acne, and fluoresces and emits light when exposed to UV light. The percentage of this fluorescence-emitted porphyrin per analysis area was calculated as the porphyrin score, and the porphyrin score before application
with IPMP alone ■ with IPMP-loaded spherical silica aerogel powder■
was used as a standard and compared to the porphyrin score after application. The results showed that the porphyrin score
increased with time when nothing was applied. The results were also compared between the application of a gel lotion containing only IPMP, a gel lotion containing only spherical silica aerogel powder, and a lotion containing IPMP- loaded spherical silica aerogel powder. As a result, the lotion containing IPMP-
loaded spherical silica aerogel powder suppressed the increase of porphyrin for a longer period of time than other lotions, and the porphyrin score remained near the initial value for five hours after application, suppressing the growth of acne bacteria. This is thought to be due to the sustained
release of IPMP from the spherical silica aerogel powder, which sustained the antibacterial effect for a long time, indicating that the prepared gel lotion is effective in actual acne prevention. Next, the slow release process of IPMP in
the gel lotion formulated with IPMP-loaded spherical silica aerogel powder over time was measured using gas chromatography. For comparison, gel lotion containing only IPMP was also measured by the same procedure. As a result, in the gel lotion formulated with IPMP alone, the release was saturated in about three hours after mixing with squalane, whereas in the lotion with IPMP-loaded spherical silica aerogel powder added, IPMP was gradually released and saturated after nine hours. These results confirm the sustained
release effect of IPMP loaded with spherical silica aerogel powder, and indicate that the formulation of spherical silica aerogel powder in gel lotion is effective. From the above study, it was found that a
sustained release effect can be obtained by loading the active ingredient into the very high porosity of the spherical silica aerogel powder. The IPMP-loaded spherical silica aerogel
powder studied in this study is expected to be utilized as a raw material for skin care products to be blended in lotions for acne-prone skin. It is also expected to be useful not only for IPMP but also for other active ingredients.
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IPMP emission (%)
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