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Abstract：
Zeta potential is often used to approximate a nanoparticle\'s surface charge, i.e., cationic, anionic, or neutral character, and has become a standard characterization technique to evaluate nanoparticle surfaces. While useful, zeta potential values provide only very general conclusions about surface charge character. Without a thorough understanding of the measurement parameters and limitations of the technique, these values can become meaningless. This case study attempts to explore the sensitivity of zeta potential measurement using specifically formulated cationic, anionic, and neutral liposomes. This study examines zeta potential dependence on pH and ionic strength, resolving power, and highlights the sensitivity of zeta potential to charged liposomes. Liposomes were prepared with cholesterol, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), and varying amounts of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS). A strong linear relationship was noted between zeta potential values and the mole percentage of charged lipids within a liposome (e.g., cationic DOTAP or anionic DOPS). This finding could be used to formulate similar liposomes to a specific zeta potential, potentially of importance for systems sensitive to highly charged species. In addition, cationic and anionic liposomes were titrated with up to two mole percent of the neutral lipid 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (lipid-PEG; LP). Very small amounts of the lipid-PEG (<0.2 mol%) were found to impart stability to the DOTAP- and DOPS-containing liposomes without significantly affecting other physicochemical properties of the formulation, providing a simple approach to making stable liposomes with cationic and anionic surface charge.
摘要：
Zeta电位通常用于近似纳米粒子的表面电荷，即，阳离子,阴离子，或中性字符，并已成为评估纳米粒子表面的标准表征技术。虽然有用，zeta电位值仅提供关于表面电荷特性的非常一般的结论。如果没有对测量参数和技术局限性的透彻了解，这些价值观可能变得毫无意义。本案例研究试图探索使用专门配制的阳离子，Zeta电位测量的灵敏度。阴离子，和中性脂质体。这项研究检查了zeta电位对pH和离子强度的依赖性，分辨率,并突出了zeta电位对带电脂质体的敏感性。脂质体是用胆固醇制备的，1,2-二硬脂酰基-sn-甘油-3-磷酸胆碱（DSPC），和不同量的1,2-二油酰基-3-三甲基铵-丙烷（DOTAP）或1,2-二油酰基-sn-甘油基-3-磷酸-L-丝氨酸（DOPS）。在zeta电位值和脂质体内带电脂质的摩尔百分比之间注意到强烈的线性关系(例如，阳离子DOTAP或阴离子DOPS)。这一发现可用于配制类似的脂质体以获得特定的ζ电位，对高度带电物种敏感的系统可能很重要。此外,用至多2摩尔%的中性脂质1,2-二硬脂酰-sn-甘油-3-磷酸乙醇胺-N-[甲氧基(聚乙二醇)-2000](脂质-PEG;LP)滴定阳离子和阴离子脂质体。发现极少量的脂质-PEG(<0.2mol%)赋予含DOTAP和DOPS的脂质体稳定性,而不显著影响制剂的其他物理化学性质。提供了一种制备具有阳离子和阴离子表面电荷的稳定脂质体的简单方法。
