Spectroscopic properties of chalcogenide fibres for biosensor applications

The spectroscopic characteristics of Te₂As₃Se ₅ infrared optical fibres are investigated. Fibres with a diameter of approximately 400 μm are tapered to produce a sensitive sensing zone and used as both a sensor and transmission line of the infrared optical signal in evanescent wave spectroscopy experiments. The fibre surface is shown to be hydrophobic, which results in enhanced detection sensitivity for nonpolar organic species in aqueous media. The peak intensity of organic species increases systematically relative to the peak intensity of water during a comparison of fibre and transmission spectroscopy experiments. A bio-optical sensor is developed by coating the fibre with human lung cells at the surface of the sensing zone. The metabolic activity of the cell is monitored spectroscopically and it is shown that the evanescent wave can locally probe the cell membrane integrity. During exposure to Triton X-100, the cell membrane signal shows a sharp decay in response to the surfactant. The ratio of methyl and methylene vibrations from membrane lipids decreases rapidly and provides a sensitive probe of the cell membrane integrity. This experiment demonstrates the capability of these fibre based bio-optic sensors to detect micromolar amounts of environmental toxicant.