Hydrogel Patches for Essential Oil Delivery in Skincare

A novel approach to hydrogel formulation can help extract the benefits of essential oils for skincare.

Plant-derived essential oils can provide valuable properties in skincare applications. For example, argan oil (AO) is known for its moisturizing and reparative properties. Passion fruit seed oil (PFSO) is rich in vitamins A and C and helps strengthen the skin barrier. Nevertheless, essential oils’ high volatility, instability, and penetration limitations present difficulties for incorporation into skincare formulations.

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Hydrogels have excellent moisture retention capabilities and can maintain sustained therapeutic concentrations of active ingredients at target sites. These properties make them useful for skincare product applications, such as face masks or under-eye patches. By leveraging deep eutectic solvents (DESs), manufacturers can incorporate essential oils into hydrogels for topical use. These solvents can enhance the water solubility of active pharmaceutical ingredients (APIs) by 6-2,200-fold compared to conventional solvents. DESs are low-melting-point mixtures that are composed of hydrogen bond donors and acceptors. Liposomal encapsulation can stabilize DESs against hydrogen-induced degradation.

Creating the Material

Researchers selected betaine-phytic acid as the DES to create a hydrogel facemask with AO and PFSO. This DES is ideal for transdermal applications, exhibiting excellent biocompatibility and minimal skin irritation. Researchers prepared samples of AO, PFSO, and mixtures of the oils in 2:1, 1:1, and 1:2 ratios.

Hydrogel swelling can cause the material to lose structural integrity over time. To verify that the material exhibited acceptable swelling behavior, researchers selected phosphate-buffered solution as the swelling medium. After seven hours, the hydrogel achieved a maximum swelling ratio of 100%, sufficient for maintaining its structural integrity.

Using an intelligent skin tester, researchers found that the pH of the hydrogels was 5.57. This falls into an acceptable range for skincare applications, as the typical pH range of skin is 4.5 to 5.5. After thirty minutes, the skin’s water and oil content increased from 48 to 54% and 27 to 35%, respectively. The researchers intended for users to wear the patch during sleep and replace it each night. They assessed it over a 12-hour period and found no significant adverse skin reactions.

As APIs gradually diffuse through the hydrogel’s polymer barrier, the material delivers long last hydration to the skin. DESs allow for a novel method of topical essential oil delivery.