Abstract: Objective To study the effects of stratum corneum on the percutaneous absorption of fluorescein sodium (NaFl) liposome in rat skin.Methods Stratum corneum was stripped off by Scotch adhesive tape,and the NaFl content in the stratum corneum and the skin with no stratum corneum were detected by spectrofluorimetry at regular intervals.The dynamic permeated amount of different preparations of NaFl in the skin at different intervals in Franz diffuse cell was determined and the distribution of NaFl at 4 h after stripping off the stratum corneum was observed by fluorescence microscope.Results The concentrations of NaFl in the stratum corneum and the skin with no stratum corneum after applying liposome NaFl preparation were significantly higher than those of NaFl solution and gel preparations (P<0.01).Also,the ratio of NaFl distribution in different skin layers changed significantly.However,compared with the control groups,the accumulated percutaneous concentrations of different liposome formulations in receiver cell of Franz diffuse cell had no significant difference (P>0.05).Conclusions It is suggested that liposome can increase and change the penetration of NaFl into the stratum corneum and the skin with no stratum corneum in vitro.Hair follicular structure may not play an important role in the drug diffusion when stratum corneum is removed.

Key words: Epidermis, Fluorescein, Liposomes, Skin absorption, Rats,Sprague-Dawley