Carbopol 980

Carbopol 980 NF, an allyl pentaerythritol crosslinked polyacrylic acid homopolymer with a molecular weight as high as 4.5 billion Daltons, Carbopol Ultrez 10 NF, polyallyl pentaerythritol-crosslinked polyacrylic acid homopolymer and Carbopol ETD 2020 NF (which is crosslinked polyacrylic acid interpolymer with a molecular weight close to 4.5 billion Daltons) (Lubrizol, Wickliffe, OH, USA), TRIS (Sigma Aldrich, Poznan, Poland), TC (Sigma Aldrich, Poznan, Poland) and demineralized, bi-distilled water were used to obtain hydrogel formulations [37 (link),38 (link)]. Model skin sebum was obtained using triglycerides of animal origin (Fagron, Warsaw, Poland), lanolin (Fagron, Warsaw, Poland), stearic acid (Sigma Aldrich, Poznan, Poland), squalene (Sigma Aldrich, Poznan, Poland) and cholesterol (Sigma Aldrich, Poznan, Poland).

The following materials were used: Hydroxypropylecellulose (Klucel ^® HF, Hercules, CA, USA), Phospholipon 90G (PL90G, Lipoid, Ludwigshafen am Rhein, Germany), Hemp Seed Oil (HSO, Pukka, Keynsham, UK), Ethanol Absolute or Ethanol 96 (ETOH, Gadot, Netanya, Israel), Propylene glycol (PG, Tamar, Rishon Lezion, Israel), dl-a- tocopheryl acetate (Vit E, Tamar, Rishon Lezion, Israel), Cannabidiol (CBD, STI pharmaceuticals, Essex, UK), Ibuprofen (Sigma, Jerusalem, Israel), Lidocaine Base (Trima, Ma′abarot, Israel), Fluorescein-5-isothiocyanate (FITC, Sigma, Jerusalem, Israel), Tween 80 (Sigma, Jerusalem, Israel), Cetyl alcohol (Holland Moran, Yehud-Monosson, Israel): Castor oil (Holland Moran, Yehud-Monosson, Israel), Cannabigerol internal standard (CBG Standard 1000 μg/mL in methanol 1 mL/ampule, Silicol, Or Yehuda, Israel), Carbopol 980 (Lubrizol, Wickliffe, OH, USA), Ammonia Solution 25% v/v (NH₄OH, Merck, Rehovot, Israel).

OXC was purchased from Euticals Spa, Italy and used as the drug molecule. Cineole (cin), N-methyl-Pyrrolidone (NMP), oleic acid (OA) and Transcutol^® P (TRC) were investigated as penetration enhancers. OA was a gift from Croda Inc., Edison, NJ, USA. TRC and Labrasol (LS) were gifts from Gattefosse Corporation, Paramus, NJ, USA. Cin, NMP, HPLC grade mEthanol and water, Propylene Glycol (PG), Polysorbate 80 (Tween 80), Isopropyl Myristate (IPM), Medium Chain Triglyceride (MCT), Polyethylene Glycol 400 (PEG-400), Sodium Lauryl Sulfate (SLS), TriEthanolamine (TEA) and formic acid were obtained from Sigma-Aldrich, Saint Louis, MO, USA. Carbopol 980 was a gift from Lubrizol, Wickliffe, OH, USA. Ethanol was procured from Decon Labs, Inc., King of Prussia, PA, USA. Phosphate-Buffered Saline (PBS) was prepared by dissolving one PBS tablet in 100 mL of water. Add SLS to PBS at 5% and pH was adjusted to 5.8. PBS tablets were purchased from MP Biomedicals, Solon, OH, USA. Dermatomed human cadaver skin from the posterior torso region of 59-year-old male was used for the ex-vivo permeation study and was supplied by New York Firefighter Skin Bank, New York, NY, USA.