Simple fiber-optic sensor based on immobilized β-cyclodextrin

A bifurcated fiber-optic sensor is reported that uses immobilized β-cyclodextrin (β-CD) as the sensing agent. The sensor forms moderately selective inclusion complexes between β-CD and many guest molecules. On complexation, a weakly fluorescent molecule often exhibits a significant increase in emission yield. The linear dynamic range of this sensor extends well over 2.5 orders of magnitude. Detection limits (signal-to-noise ratio=3) are as low as 4 nM for sample volumes as small as 15μl (60 fmol). This is an improvement of over two orders of magnitude compared with detection with a conventional "bare" fiber-optic probe. The sensor is simple to fabricate, has a useful lifetime of at least 5 months, is suitable for laser or arc lamp excitation sources and can be reconditioned rapidly.