Development, optimization, and characterization of rhein loaded nanoemulgel for treatment of osteoarthritis

This work aimed to design a transdermal delivery of rhein loaded nanoemulgel to improve the bioavailability and efficacy of rhein in the treatment of osteoarthritis and reduce its systemic side effects. Rhein loaded nanoemulsion (Rh-NE) prepared by application of ternary phase diagram and spontaneous emulsification method. Box-Behnken design (BBD) was employed to optimize formulation and preparation process of Rh-NE. The optimal formulation was 11.09% mixed oil (rhein and caproyl 90), 22.96% mixed emulsifier (kolliphor RH 40: transcutol HP, 1:1, w/w), and the preparation process was 23.08 min ultrasonic time and 179.5 W ultrasonic power. The particle size of the optimized Rh-NE was 24.5 ± 3.2 nm, PDI was 0.15 ± 0.02, and zeta potential was −18.6 ± 1.8 mV. The Rh-NE was incorporated into hydrogel consisted of 0.85% carbomer, 0.2% poloxamer 188 and 8.0% glycerol to form rhein loaded nanoemulgel (Rh-NE/Gel). In vitro transdermal flux of Rh-NE/Gel was 91.4 ± 0.9 μg/cm2·h. It was found that the inhibition rate of swelling degree of auricle caused by xylene was (54%), inhibition rate of writhing reaction was (60%), percentage increase in pain threshold was (P < 0.01), and the inhibition rate of capillary permeability was (69%). The therapeutic effect of Rh-NE/Gel on osteoarthritis in model rats was significantly improved compared with control group; the swelling degree of joint and toe were significantly reduced by 91% and 71%, respectively, and the contents of inflammatory factors IL-1β and NO were decreased 35.7% and 52.4%, respectively. The developed Rh-NE/Gel could provide anti-osteoarthritis effect and reduce the release of proinflammatory mediators in OA model rats.