Category: Formulation and Quality
Purpose: N6-furfuryladenine, also known as Kinetin is an important plant growth hormone that inhibits senescence in plants. Kinetin helps increase catalase activity, an antioxidant enzyme that helps breakdown cellular hydrogen peroxide1. It also stimulates keratinocyte proliferation and increases fibrillin and elastin deposition. Thus, it acts as a skin care molecule that helps maintain a healthy skin2. Polyvinyl alcohol (PVA) is a water soluble and biocompatible polymer having film forming ability3. In this study, we investigated the effect of different grades of PVA on the delivery of kinetin in skin.
Methods: Polyvinyl alcohol (PVA) 18-88 (EMPROVE® exp Ph Eur, USP, JPE), PVA 26-88 (EMPROVE® exp Ph Eur, USP, JPE) and PVA 40-88 (EMPROVE® exp Ph Eur, USP, JPE) were gifted by MilliporeSigma. 0.1%w/v Kinetin was added to a solvent composition of DMSO: Propylene glycol: Water which was in the ratio of 15: 25: 60. The solution was heated to 90℃ and PVA (10%w/w) was added to it. The temperature of this mixture was maintained at 90℃ for 2hrs to allow complete dissolution of PVA. The gel thus formed was blended gently using a vertical blender.
Dermatomed human skin mounted on Franz diffusion cells was used for the permeation studies. The receptor chamber contained 1X PBS that helped maintain sink conditions. Donor contained 100µL of PVA gel. Skin concentration of kinetin was determined by separating epidermis and dermis, subjecting them to extraction with DMSO. Samples were analyzed using High Performance Liquid Chromatography (HPLC). Gels were characterized for Tack using the TA.XT Express Texture Analyzer. pH of the gels was measured to determine the impact of molecular weight on the resulting acidity of the formulation.
Results: Kinetin delivery to the epidermis (Figure 1) was significantly higher in PVA 18-88 (0.115±0.009µg) than PVA 40-88 (0.037±0.002µg). However, there was no significant difference in the amount of kinetin delivered to the dermis across groups. pH of all the gels was found to be 6.2±0.11. Tack test revealed that the separation distance for all gels was found to be 1.2±0.3mm. There was no significant difference in the absolute force values across grades of polymer in the tack test.
Conclusion: Higher epidermal delivery indicates that grade of the polymer may have an impact on the delivery of Kinetin. Results for pH showed that grade of the polymer had little impact on the acidity of the formulation. However, the group with the highest molecular weight (PVA 40-88) had the highest absolute force value in the tack test.