Design, characterization, and release profile of a cannabidiol (CBD)-rich polyvinyl alcohol hydrogel

Abstract

Cannabidiol (CBD) has been reported to have a plethora of therapeutic opportunities in many diseases. Current CBD delivery systems include suspension, emulsion, or nanoparticles, which enable the rapid release of CBD. However, in some cases, long-term exposure to drugs is preferred, such as in controlling inflammation. This study aimed to prepare a CBD-rich hydrogel that exhibits controlled and sustained release of CBD while maintaining CBD bioactivity. Herein, PVA mixed with propylene glycol (PG) or vegetable glycerine (VG) in the presence of CBD were used to fabricate hydrogels through a cyclic freeze–thaw process. The successful loading of CBD inside the PVA gel was macroscopically demonstrated by the uniform pink color of the gel and chemically identified by the characteristic absorptions of CBD at 1630 and 1585 cm⁻¹ in Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) revealed small, fine pores dispersed throughout the gels when PG or VG was added. Differential scanning calorimeter (DSC) curves showed that the gels containing VG were more amorphous than those without VG. Thermogravimetric analyzer (TGA) results showed that the CBD-containing gels were stable up to 100 °C when they started to lose water and up to about 200 °C when they started to lose other molecules such as PG, indicating a good shelf-life. A compression test showed that the hydrogel was soft and could tolerate more than 60% deformation and 45 kPa pressure. CBD in vitro release assessment through ultraviolet-visible (UV-vis) spectrophotometer and UPLC-MS/MS analysis demonstrated that the hydrogel can continually release CBD for at least 24 h. Adding VG could significantly reduce PVA crystallinity and promote the release of CBD from the hydrogel into an aqueous solution; adding PG and VG together can regulate the release rate of CBD. Finally, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay proved that the CBD released from the hydrogels through 24 h had good antioxidant activity. Considering the biocompatible nature of PVA, the CBD-enriched PVA hydrogels developed in this study can be used to topically deliver CBD to tissues or the body to treat inflammation and promote wound healing.