Penetration Study of CBD with an in-vitro Skin Model

Introduction

Cannabidiol (CBD) use in cosmetics and personal care has increased significantly since 2017. In order for topical products containing CBD to be effective, they must deliver CBD to the receptors located in the epidermis. Delivery of CBD to the epidermis is determined by the carrier oils used. An in-vitro skin model was used to assess the penetration of 1% CBD in five carrier oils: Neossance® Squalane, sunflower oil, hemp seed oil, caprylic/capric triglycerides (CCT), and jojoba oil. The amount of CBD in the epidermis was measured by HPLC at 4 time points: 1, 3, 6, and 24 hours. Neossance Squalane delivered the most CBD into the epidermis across all time points, whereas CCT delivered the least.   

Method

The ability of carrier oils to facilitate skin penetration of CBD was evaluated using an in-vitro model of human skin. A commercially available in– vitro reconstructed human epidermis from normal human keratinocytes (EpiSkinTM) was used according to the manufacturer’s instructions.  

Test samples were prepared by mixing CBD in one of five carrier oils: Neossance Squalane, sunflower oil, hemp seed oil, caprylic/capric triglycerides (CCT), and jojoba oil at 1% w/w concentration.  

The three-dimensional cultured skins (EpiSkin) were plated in the wells of the 12 well plates and conditioned overnight in maintenance medium. The maintenance medium was replaced with 2 mL of 1% Tween in PBS(-) solution for each well, and 0.15 mL of the test sample was applied to the stratum corneum of the skin model and incubated at 37°C for 1, 3, 6, or 24 hours. At each time point, the test sample was removed from the surface of the skin and washed five times with 0.5 mL of the respective carrier oil. 

For each test sample, three distinct types of samples were collected (skin cells, receptor fluid, and washing fluid) in triplicate at various time points (1, 3, 6, and 24 hours) and the amount of CBD in each sample was measured. For the skin cell samples, the washed cells were transferred to an Eppendorf tube and 1 mL of ethanol and a stainless-steel bead was added. The skin cells were then grinded with a TissueLyser, and diluted with isopropanol up to a volume of 50 mL. The amount of CBD in each sample type (skin cells, receptor fluid, and washing fluid) was determined by HPLC.  

Results

The amount of CBD measured in the skin cell fraction of the model at various time points for each carrier oil is shown in Figure 1. Neossance Squalane facilitated faster and greater penetration and delivery of CBD into the skin over the 24 hour period of the experiment.  In contrast, all of the other carrier oils demonstrated much lower penetration rates of CBD over the same time period. The amount of CBD delivered for each carrier oil is provided in Table 1, along with the percent of CBD delivered compared to Neossance Squalane at the 24 hour time point.  

Conclusion

This study demonstrates that Neossance Squalane greatly enhances CBD penetration into the epidermis. Delivery is critical to CBD product effectiveness as cannabinoids receptors are located within the epidermis. Neossance Squalane is proved to enable immediate penetration and, overall, deliver 10 to 40 times more CBD to the epidermis than sunflower oil, hemp seed oil, CCT, and jojoba oil over a 24-hour period. 

Acknowledgements

This study was carried out at the COSMOS TECHNICAL CENTER, a leading R&D Center within NIKKOL GROUP. We would like to thank Mr. Daisuke Yoshida and the R&D team for the excellent technical support.