Determination of Drug and Fatty Acid Binding Capacity to Pluronic F127 in Microemulsions

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• 作者：Monica A. James-Smith ; Dushyant Shekhawat ; Brij M. Moudgil ; Dinesh O. Shah
• 刊名：Langmuir
• 出版年：2007
• 出版时间：February 13, 2007
• 年：2007
• 卷：23
• 期：4
• 页码：1640 - 1644
• 全文大小：143K
• 年卷期：v.23,no.4(February 13, 2007)
• ISSN：1520-5827

文摘

We propose that one can deduce very insightful information regarding the drug and fatty acid binding capacity ofmicroemulsions through simple turbidity experiments. Pluronic F127-based oil-in-water microemulsions of variouscompositions were synthesized and titrated to turbidity with concentrated amitriptyline, an antidepressant drug. Weobserved that, above certain Pluronic F127 concentrations, turbidity was never observed, irrespective of how muchamitriptyline was added to the microemulsion. We also observed that whenever sodium caprylate fatty acid was notincluded in the microemulsion formulation, turbidity never occurred. On the basis of these findings, we were ableto determine the point at which all sodium caprylate present in the microemulsion formulation was bound to the F127in the microemulsion (i.e., no fatty acid was free in the bulk in monomer form). By the same logic we were also ableto determine how much amitriptyline was binding to the microemulsions. We also measured the dynamic surfacetension, foamability, and fabric wetting time of the microemulsion formulations to further prove the hypothesis thatall fatty acid is bound to the F127 in the microemulsion above a critical Pluronic F127 concentration. On the basisof this research, we have concluded that there are approximately 11 molecules of sodium caprylate fatty acid boundper molecule of Pluronic F127 and approximately 12 molecules of amitriptyline bound per molecule of Pluronic F127in the optimal microemulsion formulation. These findings give us valuable information about the charge density atthe oil/water interface and about the mechanism of binding of the drug to the microemulsion.