| Tea is rich in a lot of chemical components. Tea polyphenols(TP), a polyphenoliccompound extracted from tea, has a wide range of pharmacological activity such asantioxidant, anti-radiation, antibacterial, antiviral, antidiabetic, anti-aging and so on. However,the widespread application of tea polyphenols is limited by its poor stability, prone tooxidation with concomitant loss of biological activity, because of its polyphenol structure. Inthis study, the tea polyphenols are prepared into flexible liposomes in order to solve thisproblem and make full use of its antioxidant, anti-radiation, anti-aging functions. This studyof preparation technique is to improve its stability and percutaneous penetration performanceand increase its application value in cosmetics.This paper was designed to prepare tea polyphenols-loaded flexible liposomes using eggyolk lecithin(EPC) and cholesterol(CH) as membrane material, sodium cholate hydrate(SCH)as softener by reversed-phase evaporation. The study mainly includes:(1) Teapolyphenols-loaded flexible liposomes were prepared by reversed-phase evaporation methodwith encapsulation efficiency(EE%) as the evaluation. The effect of ratio of lecithin tocholesterol(EPC/CH ratio), the ratio of lecithin to tea polyphenol(EPC/TP ratio), the ratio oflecithin to sodium cholate hydrate(EPC/SCH ratio), the ratio of aqueous to organicphase(W/O ratio), pH value of PBS, ultrasonic time were investigated as single factorexperiments.(2) On the basis of single factor experiments, the preparation conditions wereoptimized by response surface experiment with three influential factors for encapsulationefficiency.(3) Tea polyphenols-loaded flexible liposomes prepared by the optimal conditionswere characterized. The liposomes were determinated on particle size, surface morphology,zeta potential, thermal performance and release properties by dynamic light scatteringinstruments, field-emission transmission electron microscopy(SEM), zeta potentiometer,comprehensive thermal analyzer.(4) The transdermal delivery of tea polyphenols-loadedflexible liposomes across rat skin was studied in vitro with cumulative release amount as theevaluation. The effect of the ratio of lecithin to cholesterol, the ratio of lecithin to teapolyphenols, the ratio of lecithin to sodium cholate hydrate were investigated to study theinfluence of different preparation prescription of the flexible liposomes on percutaneouspenetration.The results showed that: the single factor experiment and the response surfaceexperiment were used to optimize the preparation process of tea polyphenols-loaded flexibleliposomes. The optimal preparation conditions were determined: EPC/CH ratio was3.82:1， EPC/TP ratio was2.68:1，W/O ratio was4.34:1. Under these conditions, the evaluatedentrapment efficiency of the liposomes was (57.37±1.04)%while the theoretical optimalentrapment efficiency was57.26%. The tea polyphenols-loaded flexible liposomes werevesicle with regular shape. The average size was171.2nm, the size distribution was narrowand the zeta potential was-53.5mV. The combination of tea polyphenols with the liposomeswas physical interaction. The tea polyphenols-loaded flexible liposomes had a good sustainedrelease property. The release behavior of liposomes was fitted to the first order kineticsequation. Permeation experiments in vitro showed that tea polyphenols-loaded flexibleliposomes with softener could improve the transdermal penetration performance. Thepermeability of liposomes increased as the amount of sodium cholate hydrate(SCH) increasedwhen the EPC/SCH ratio was less than4:1. The permeability of liposomes was inverselyproportional to the addition of cholesterol and was proportional to the addition of teapolyphenols. |
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