Development Of Resveratrol Microemulsion-based Gels For Vaginal Delivery

Background and purposeResveratrol(Res)is a natural polyphenol compound which has anti-inflammatory and antioxidant effects.Res exerts anti-inflammatory effects by reducing inflammatory factors,reducing the generation of free radicals in inflammatory sites,and affecting the energy metabolism of Trichomonas vaginalis.However,Res has poor water solubility,first-pass effect by oral administration,light instability,which limit its clinical application.In this study,common gel of microemulsion and thermosensitive gel of microemulsion were designed to increase the solubility and stability of the drug.Microemulsion-based gels were administered through the vagina,which can directly affect the diseased area and increase the drug retention in the vagina.In addition,vaginal administration for vaginal inflammation can avoid first-pass effects caused by oral administration.MethodsIn this study,Res microemulsion was prepared and optimized by pseudo ternary phase diagram and determination of drug loading.The appearance of Res microemulsion was observed with a transmission electron microscope.The particle size and distribution of Res microemulsion was measured using a Malvern Zetasizer.Chitosan hydrochloride and Poloxamer 407 were selected as the gels matrix of common gel of resveratrol microemulsion(Res-ME-Cogel)and thermosensitive gel of resveratrol microemulsion(Res-ME-Tsgel),respectively.The drug content of Res in Res-ME-Cogel and Res-ME-Tsgel were determined by high performance liquid chromatography.The p H of Res-ME-Cogel and Res-ME-Tsgel were measured with a p H meter.The gelation temperature of Res-ME-Tsgel was investigated by the tube inversion method.Simulated vaginal fluid including 0.3% Tween 80 was used as the release medium.In vitro release studies were performed using dialysis to investigate the in vitro release behavior of Res-ME-Cogel and Res-ME-Tsgel.The released curves were fitted with a mathematical model.The stability of Res-ME-Cogel and Res-ME-Tsgel were examined at 25°C and 4°C for 30 days.The safety of Res-ME-Cogel and Res-ME-Tsgel was investigated by the skin allergy test and vaginal irritation test.The SD rats were given Res-ME-Cogel,Res-ME-Tsgel by vaginal administration and Res solution by the tail vein injection to investigate the distribution of Res in rat vaginal tissue.ResultsThe largest prescription in the self-emulsifying region of the pseudo ternary phase diagram was selected,ethyl oleate as the oil phase,emulsifier OP-10 as emulsifier,and 1,2-propylene glycol as the co-emulsifier.The drug loading determined the ethyl oleate:emulsifier OP-10:1,2-propylene glycol was 20:60:20 in Res microemulsion.Under the transmission electron microscop,freshly prepared Res microemulsion was observed to be non-aggregating,non-adhesive,good dispersibility,small particle size and uniform particle size distribution.The average particle size and polydispersity index of Res microemulsion were 12.12 ± 3.12 nm and 0.045.When the ratio of 5% chitosan hydrochloride to microemulsion was 6:1,Res-ME-Cogel was a uniform,transparent gel.Res-ME-Tsgel was formed when the ratio of 17% of Poloxamer 407 to microemulsion was 6:1.Res-ME-Tsgel gelled at 33°C,so it was solution at room temperature,and quickly formed after vaginal administration.The average drug content of Res-ME-Cogel and Res-ME-Tsgel were 4.88 ± 0.07 mg/g and4.88 ± 0.08 mg/g.The p H values were 4.17 ± 0.01 and 5.21 ± 0.04,which were suitable for vaginal administration.Res-ME-Cogel,Res-ME-Tsgel had no significant changes in p H,content,and appearance at 25°C and 4°C for 30 days.In vitro release study,the cumulative release of Res-ME-Cogel and Res-ME-Tsgel reached 79.66 ±2.72% and 85.44% ± 4.79 in 120 h,and the Res solution released 96.78 ± 4.30% in 6h.The drug release curves of Res-ME-Cogel and Res-ME-Tsgel were fitted to the first-order kinetic equation.When Res-ME-Cogel and Res-ME-Tsgel were administered to rats through the vagina after 1 h,the retention of Res in the vagina were 2.88 μg/g and 3.17 μg/g.The retention of Res in the vagina were 1.69 μg/g and3.80 μg/g after 12 h.After 24 h,the retention of Res in the vagina were 0.52 μg/g and1.49 μg/g.After 12 h,the retention of Res in the Res-ME-Tsgel group was 2.25 times that of Res-ME-Cogel,and after 24 h was 2.87 times.When the Res solution was injected into the tail vein,the retention of Res in the vagina was 0.91 μg/g after 6 min,0.58 μg/g after 15 min,and 0.22 μg/g after 30 minutes,respectively.ConclusionsThis study successfully prepared two kinds of gels,one was Res-ME-Cogel,which was a uniform transparent gel,and the other was Res-ME-Tsgel,which was a transparent liquid solution at room temperature,and could quickly form a gel at 37°C.Compared with Res solution,Res-ME-Cogel and Res-ME-Tsgel had a sustained release effect.The formulations had good storage stability at 4°C and 25°C.Res-ME-Cogel and Res-ME-Tsgel could not cause skin sensitization and had no irritation to the vaginal mucosa after one or multiple administrations,so the safety of the preparations were good.Compared with the tail vein injection of Res solution,the amount and duration of Res retention in the vagina in the vaginal administration of Res-ME-Cogel and Res-ME-Tsgel are more and larger.