Polarization-based sensing of glucose using an oriented reference film

We describe a new approach to glucose sensing using polarization measuremen ts in the presence of a stretch-oriented reference film. The method relies on measurement of the polarized emission from the reference film and of a f luorophore which changes intensity in response to glucose. A glucose-sensit ive fluorescent signal was provided by the glucose/galactose binding protei n from E. coli. This protein was labeled with an environmentally sensitive fluorophore at a single genetically inserted cysteine residue, and displaye d decreased fluorescence upon glucose binding. Using the protein and the re ference film we observed glucose-sensitive polarization values for micromol ar glucose concentrations. This method of polarization-based sensing is gen eric and can be used for any sensing fluorophore which displays a change in intensity. In principle, one can construct simple and economical devices f or this type of glucose measurement. (C) 1999 Society of Photo-Optical Inst rumentation Engineers. [S1083-3668(99)01204-6].