Analytical Sciences

Determination of the Electrostatic Potential of Oil-in-Water Emulsion Droplets by Combined Use of Two Membrane Potential-Sensitive Dyes

Tomoya IWATA,* Hirohisa NAGATANI,** and Toshiyuki OSAKAI*

*Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501, Japan
**Faculty of Chemistry, Institute of Science and Engineering, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan

The fluorescence behaviors of potential-sensitive dyes including anionic DiBAC₄(3) (denoted by dye A), DiSBAC₂(3) (dye B), and zwitterionic di-4-ANEPPS (dye C) were studied in oil-in-water (O/W) emulsions. In this study, the equilibrium Galvani potential difference (Δ_O^Wφ_eq) of the O/W-emulsion droplets was controlled by changing the ratio of the concentrations of electrolytes added to the O (=1,2-dichloroethane) and W phases. When using an adequate combination of the dyes, i.e., B and C, we could observe that the ratio of their fluorescence peak intensities was changed from 1.08 to 1.38, depending on the change of (Δ_O^Wφ_eq from 26 to 73 mV. It is desirable to apply this method to study the potential-dependent ion or electron-transfer reactions occurring at vesicles or liposomes, and also to biomembranes.

J-STAGE: View this article in J-STAGE