Experimental and Molecular Dynamics Investigation into the Amphiphilic Nature of Sulforhodamine B

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• 作者：Baris E. Polat ; Shangchao Lin ; Jonathan D. Mendenhall ; Brett VanVeller ; Robert Langer ; Daniel Blankschtein
• 刊名：Journal of Physical Chemistry B
• 出版年：2011
• 出版时间：February 17, 2011
• 年：2011
• 卷：115
• 期：6
• 页码：1394-1402
• 全文大小：1080K
• 年卷期：v.115,no.6(February 17, 2011)
• ISSN：1520-5207

文摘

Sulforhodamine B (SRB), a common fluorescent dye, is often considered to be a purely hydrophilic molecule, having no impact on bulk or interfacial properties of aqueous solutions. This assumption is due to the high water solubility of SRB relative to most fluorescent probes. However, in the present study, we demonstrate that SRB is in fact an amphiphile, with the ability to adsorb at an air/water interface and to incorporate into sodium dodecyl sulfate (SDS) micelles. In fact, SRB reduces the surface tension of water by up to 23 mN/m, and the addition of SRB to an aqueous SDS solution induces a significant decrease in the cmc of SDS. Molecular dynamics simulations were conducted to gain a deeper understanding of these findings. The simulations revealed that SRB has defined polar 鈥渉ead鈥?and nonpolar 鈥渢ail鈥?regions when adsorbed at the air/water interface as a monomer. In contrast, when incorporated into SDS micelles, only the sulfonate groups were found to be highly hydrated, suggesting that the majority of the SRB molecule penetrates into the micelle. To illustrate the implications of the amphiphilic nature of SRB, an interesting case study involving the effect of SRB on ultrasound-mediated transdermal drug delivery is presented.