Analytical Sciences

Transduction of Analytical Signals by Supramolecular Assemblies of Amphiphiles Containing Heterogeneously

John D. BRENNAN*, R. StephenBROWN** and Ulrich J. KRULL*** *

*Department of Chemistry,Brock University, St. Catharines, Ontario, Canada, L2S 3A1
**Department of Chemistry, Queen's University, Kingston, Ontario, Canada,K7L 3N6
***Chemical Sensors Group, Department of Chemistry, Erindale Campus,University of Toronto,3359 Mississauga Road North, Mississauga, Ontario, Canada L5L lC6

We report on the development and characterization of supramolecularassemblies of amphiphiles which are able totransduce changes of pH into optical signals. A series of assemblies havebeen investigated, including vesicular bilayerlipid membranes, monolayer films of fatty acids or phospholipids at theair-water interface, and covalently immobilizedalkylsilane monolayers. In all cases, these membrane assemblies were formed from mixtures of species havingzwitterionic and ionizable headgroups. In addition, a small amount of thefluorescently labeled phospholipidnitrobenzoxadiazole phosphatidylethanolamine (1 - 3%) was incorporated intothe membranes. This resulted in systemswhich were able to transduce alterations of pH into changes in fluorescenceintensity. Investigations into the physicalmechanism responsible for alterations of fluorescence intensity from suchmembranes suggested that the nitro-benzoxadiazolephosphatidylethanolamine (NBD-PE) signal was based on changes ofself-quenching of the probe whichoccurred when the physical and electrostatic characteristics of themembranes were altered. Useful signals were obtainedonly when microscopic phase separation existed within the membranes,indicating that careful design of the membranewas required to optimize the signal generated. (Keywords: Fluorescence, phase separation, membrane, biosensor,transducer)

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