The Study Of Transfersomes Gel For Topical Delivery Of Tacrolimus And Preliminary Pharmacodynamics Evaluation

Tacrolimus was an insoluble and macromolecular drug which was difficult to gainaccess to deep-layer tissue of skin and play a therapeutic role. Transfersomes wereself-aggregation vesicles by prescription improvement based on liposomes. The lipidmembrane of transfersomes owned high ability of deformation and could deformspontaneously to pass through narrow holes which were5to10times less than their owndiameters. This paper aimed to use transfersomes to carry tacrolimus through the skin holesand increase the retentions of drug in the epidermis and dermis. Specific research contentswere as follows.During the pre-formulation study, an HPLC method with acetonitrile: water （60:40,v/v）as mobile phase,60℃as column temperature and measurement wavelength as210nmwas developed for the assay of tacrolimus. The HPLC method was accurate and reliable.Solubility and oil-water partition coefficients in different medium were measured. Theresults showed relatively strong lipophilic property of tacrolimus and the diffusion inepidermis and dermis was the main limiting step of its percutaneous absorption.Tacrolimus loaded transfersomes were prepared by film dispersion method. Theentrapment efficiency and particle size were taken as criterions to evaluate the effects ofsorts of surfactant, lipid-drug ratio, Tween-80-phospholipid ratio, ultrasonic power andtime, and pH of aqueous phase. Main factors affecting qualities of tacrolimus loaded transfersomes （Lipid-drug ratio, Tween-80-phospholipid ratio and ultrasonic time） werescreened and the Box-Behnken response surface method was used to optimize thepreparations. The entrapment efficiency and diameters of the optimal transfersomes were85.9%and110.8nm.In order to make more comprehensive evaluations of tacrolimus loaded transfersomes,entrapment efficiency was determined by dialysis method and the particle size and zetapotential of transfersomes were measured employing DelsaNano C particle size instrument.The nearly-circular morphology of transfersomes was observed by transmission electronmicroscope. Deformation experiment results showed that deformation ability oftransfersomes was stronger than liposome in vitro. Centrifugal acceleration experimentresults indicated that transfersomes suspension had certain stability. The accumulativeretentions of tacrolimus for transfersomes in the epidermis and dermis were improvedsignificantly, that were （2.30±0.32） μg·cm^-2and （1.75±0.21） μg·cm^-2. They were3.8times and5.8times as much as tacrolimus ointment,2.2times and2.7times as much asliposomes.Carbopol940was used as matrix in preparing tacrolimus transfersomes gel and theobtained gel was in milky white and uniform semi-solid state. The drug content intransfersomes gel was0.982mg·g^-1. Cumulative drug release for tacrolimus transfersomesgel after12h of drug release study in vitro was37.6%. In vitro percutaneous permeationexperiments, the drug rententions of transfersomes gel in the epidermis and dermis wereless than transfersomes suspensions. The transfersomes gels were still3.2times and4.5times the drug rententions of ointments. They were2.3times and2.9times as comparedwith liposomes gel. Preliminary stability results showed the transfersomes gel should bepreserved in low temperature environment, as high temperature would affect the quality oftransfersomes gel.Repeated topical applications of DNFB were used to induce eczema and drugtreatments were conducted for7days. Results showed that the transfersomes gel had thebest treatment effect with thinning of the ear and new hair growing at back damaged skin.The histopathology of the skin showed the thickness of skin layer became significantly thinner and the amounts of inflammatory cells nucleus reduced.Skin irritation experiments indicated that tacrolimus transfersomes gel had no obviousirritation to the skin after single or multiple dosages.In conclusion, tacrolimus transfersomes gel obtained in this study was stable and hadno obvious skin irritation. The tacrolimus transfersomes gel could obviously increase theamounts of drug retention in epidermis and dermis, and had good treatment for eczema.This study would lay the foundation for further research and development of tacrolimustransfersomes gel.