Laboratory of Pharmaceutical Technology, Department of Pharmacy, School of Health Sciences, University of Patras, 26510 Rio, Greece.
Langmuir. 2009 Aug 4;25(15):8480-8. doi: 10.1021/la804305z.
Rheological properties of complex hydrogels containing different amounts of liposomes and/or cyclodextrin (CD) were evaluated. Sonicated unilamellar vesicles (SUV) were loaded in a hydrogel composed of Carbopol 974 NF and hydroxyethylcellulose (Natrosol 250 HX). Phosphatidylcholine (PC) and hydrogenated-PC (HPC) liposomes, both mixed with cholesterol in a 2:1 lipid/chol mol ratio, were used. In some cases, hydroxypropyl-beta-cyclodextrin was also added (100 or 400 mg/mL). Gels were incubated at 40 degrees C/75% humidity for 7 days or 1 month to evaluate the effect of aging on their rheological properties. FTIR and DSC studies were performed to investigate possible interactions between the polymers and CD molecules at different CD concentrations. Static and dynamic rheological measurements were carried out. All gels had shear-thinning behavior (fitted well by the Cross model) with the exception of gels containing high concentrations of CD that were transformed into nonflowing elastic sticky solids, especially after aging. The more pronounced elastic behavior of gels containing 400 mg/mL CD is reflected by the higher values of relaxation strengths over all relaxation times. Complete interaction between polymers and CD, in the high-CD-content gels, as proven by FTIR and DSC studies, explains the dominating contribution of CD on gel characteristics. The addition of liposomes to such CD-containing gels has a substantial effect on their rheological properties, which are dependent on the liposome type (HPC/chol liposomes > PC/chol) and the lipid/CD ratio. This is explained by the "neutralization" of some CD molecules that prefer to interact with chol molecules that they extract from the lipid membranes. Gels with a high CD concentration (400 mg/mL) are almost insensitive to aging, whereas all other gels become slightly more elastic and less viscous as aging proceeds.
评价了含有不同量脂质体和/或环糊精（CD）的复合水凝胶的流变性能。超声处理的单层囊泡（SUV）被加载到由 Carbopol 974 NF 和羟乙基纤维素（Natrosol 250 HX）组成的水凝胶中。使用了混合有胆固醇的磷脂酰胆碱（PC）和氢化 PC（HPC）脂质体，脂质/胆固醇摩尔比为 2:1。在某些情况下，还添加了羟丙基-β-环糊精（100 或 400mg/mL）。凝胶在 40°C/75%湿度下孵育 7 天或 1 个月，以评估老化对其流变性能的影响。进行了傅里叶变换红外光谱（FTIR）和差示扫描量热法（DSC）研究，以研究不同 CD 浓度下聚合物和 CD 分子之间可能存在的相互作用。进行了静态和动态流变学测量。所有凝胶均表现出剪切稀化行为（通过 Cross 模型拟合良好），除了含有高浓度 CD 的凝胶外，这些凝胶在老化后转化为非流动弹性粘性固体，尤其是在老化后。在含有 400mg/mL CD 的凝胶中，弹性行为更为明显，这反映在所有松弛时间内的松弛强度值更高。FTIR 和 DSC 研究证明，在高 CD 含量凝胶中聚合物与 CD 之间完全相互作用，解释了 CD 对凝胶特性的主要贡献。将脂质体添加到此类含有 CD 的凝胶中会对其流变性能产生重大影响，这些性能取决于脂质体类型（HPC/胆固醇脂质体> PC/胆固醇）和脂质/CD 比。这可以解释为一些 CD 分子被“中和”，这些 CD 分子更喜欢与它们从脂质膜中提取的胆固醇分子相互作用。高 CD 浓度（400mg/mL）的凝胶对老化几乎不敏感，而其他所有凝胶随着老化的进行，会变得稍微更具弹性且粘性更小。
