Manosroi A, Thathang K, Werner R G, Schubert R, Manosroi J
Faculty of Pharmacy, Chiang Mai University, Chiang Mai 50200, Thailand.
Int J Pharm. 2008 May 22;356(1-2):291-9. doi: 10.1016/j.ijpharm.2008.01.001. Epub 2008 Jan 9.
Characteristics and physical stability of luciferase plasmid (pLuc) entrapped in cationic bilayer vesicles prepared from various molar ratios of amphiphiles (DPPC, Tween61 or Span60), cholesterol (Chol) and cationic charge lipid (DDAB) were investigated. The cationic liposomes were composed of DPPC/Chol/DDAB in the molar ratio of 7:2:1. The cationic (Tween61 or Span60) niosomes were composed of Tween61/Chol/DDAB or Span60/Chol/DDAB in the molar ratio of 1:1:0.05. The maximum loading of pLuc was 15.29, 22.70, and 18.92 microg/mg of the total lipids or surfactants of liposomes, Tween61 and Span60 niosomes, respectively. The morphology of the vesicles showing multilamellar structure was characterized by transmission electron microscope (TEM). The particle sizes of the vesicles in nanosize range (160-850 nm) were determined by Photon Correlation Spectroscopy (PCS). Gel electrophoresis and gel documentation were modified to determine the entrapment efficiency of pLuc in cationic bilayer vesicles. The cationic bilayer vesicles gave the pLuc entrapment efficiency of 100%. The pLuc entrapped in cationic liposomes exhibited higher stability than pLuc in solution and pLuc entrapped in cationic Tween61 or Span60 niosomes, when stored at 4, 30 and 50 degrees C for 8 weeks. After 8 weeks at 4 degrees C, pLuc contents remained in cationic liposomes was 2 and 3 times higher than cationic Span60 and Tween61 niosomes, respectively. After 3 weeks, 50 and 2% of pLuc was remained in cationic liposomes at 30 and 50 degrees C respectively, whereas all pLuc in cationic Span 60 and Tween61 niosomes were degraded within 2 and 1 week, respectively. At 30 and 50 degrees C, pLuc in an aqueous solution or in bilayer vesicular formulations were not in a stable supercoil form. This study has indicated that the stability of pLuc can be enhanced by entrapping in cationic liposomes more than in niosomes. Higher temperature with increase storage time can affect the stability of pLuc even entrapped in bilayer vesicles.
研究了由不同摩尔比的两亲物（二棕榈酰磷脂酰胆碱（DPPC）、吐温61或司盘60）、胆固醇（Chol）和阳离子脂质（二甲基双十八烷基溴化铵（DDAB））制备的阳离子双层囊泡中包裹的荧光素酶质粒（pLuc）的特性和物理稳定性。阳离子脂质体由摩尔比为7:2:1的DPPC/Chol/DDAB组成。阳离子（吐温61或司盘60）非离子脂质体由摩尔比为1:1:0.05的吐温61/Chol/DDAB或司盘60/Chol/DDAB组成。pLuc在脂质体、吐温61和司盘60非离子脂质体的总脂质或表面活性剂中的最大负载量分别为15.29、22.70和18.92μg/mg。通过透射电子显微镜（TEM）表征了显示多层结构的囊泡形态。通过光子相关光谱法（PCS）测定了纳米尺寸范围（160 - 850nm）内囊泡的粒径。对凝胶电泳和凝胶成像进行了改进，以测定pLuc在阳离子双层囊泡中的包封率。阳离子双层囊泡的pLuc包封率为100%。当在4、30和50℃储存8周时，包裹在阳离子脂质体中的pLuc比溶液中的pLuc以及包裹在阳离子吐温61或司盘60非离子脂质体中的pLuc表现出更高的稳定性。在4℃储存8周后，阳离子脂质体中残留的pLuc含量分别比阳离子司盘60和吐温61非离子脂质体高2倍和3倍。在30℃和50℃储存3周后，阳离子脂质体中分别残留50%和2%的pLuc，而阳离子司盘60和吐温61非离子脂质体中的所有pLuc分别在2周和1周内降解。在30℃和50℃时，水溶液或双层囊泡制剂中的pLuc不是稳定的超螺旋形式。这项研究表明，将pLuc包裹在阳离子脂质体中比包裹在非离子脂质体中能增强其稳定性。随着储存时间增加，温度升高会影响即使包裹在双层囊泡中的pLuc的稳定性。
