| Glutathione (GSH), a bioactive three-peptide, which has broad application in food industry, clinical medicine and biology-related areas, shows miscellaneous biological functions in vivo. However, GSH is easy to oxidize and hard to go through the cell membrane,which limit its application greatly. In order to improve the stability and extend the shelf life of GSH, the preparation methods of GSH nano-liposome and pro-liposome were studied in this paper.Firstly, the preparation feasibility of GSH nano-liposome was studied. GSH showed good solubility in water, for the apparent partition coefficient of GSH in acidified n-octanol/ water system was far less than -0.3.The membrane material of liposome (phospholipid, cholesterol and Tween 80) and the liposome preparing process (rotatory evaporation, pH adjusting and sonication) showed little influence on the stability and activity of GSH. Therefore, liposome could be used to entrap GSH.In order to determine entrapment efficiency , Gel filtration was used to separate GSH liposome from free GSH. The average recovery of GSH with the GSH solutions of different concentrations was about 94.0% with 0.05 mol/L PBS(contained 0.5 mol/L NaCl) as eluting reagent. Four methods preparing GSH liposome, pH gradient, reverse phase evaporation, ethanol injecting and ether injecting, were compared by encapsulation efficiency, particle size, polydispersity index (PDI) and storage stability. pH gradient method was chose to prepare GSH liposome.The optimal processing parameters of preparing GSH liposome by pH gradient method were: pH gradient from 3.0 to 6.0, hydration temperature 40℃, hydration time 30min,sonication intensity 200W and time 5min. Moreover, the optimal formula of preparing GSH liposome was GSH loading capacity 25%, cholesterol/phospholipids: 0.25/1(W/W), Tween 80/phospholipid: 0.5/1(W/W), ether/ citric acid buffer: 3/1(V/V). The encapsulation efficiency of the GSH liposome product was 90.3% prepared by the above parameters. And the GSH liposome showed good microcosmic conformation and even spreading vesica, average particle size 102.1nm, PDI 0.031. Then the stability of GSH liposome under different storage conditions was studied. The temperature showed the strongest influence and the best storage temperature was 4℃.The cryprotectants used for the preparation of GSH pro-liposome were selected, and the results showed that the cryprotecting effect of the mannitol was the best in the seven cryprotectants. When mannitol/ phospholipid was 15:1(W/W), the GSH pro-liposome had a even color, intense structure, full shape, and with encapsulation efficiency being 85.4%, retention ratio reaching 88.1% and particle size being 469.9nm after rehydration.GSH pro-liposome was analyzed by FTIR infrared spectrum , the result showed that mannitol could protect the integrality of liposome membrane. When the GSH pro-liposome stored under 20℃and 40℃for 30 days, the particle size, encapsulation efficiency, pH and MDA had no significant changes, and the storage stability was good; thus, it was revealed that pro-liposome improved the stability of liposome. The results of hygroscopic equilibrium test showed that low humidity had little impact on the stability of GSH pro-liposome while high humidity had strong impact on it, so GSH liposome freeze-drying powder should be stored in dry or low humid environment.
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