Local real-time detection of pH using fibre tapers

摘要

A size of tapered silica fibre probes makes them suitable for exploration of small objects, as e.g. cells. Fibre-optic probes of enhanced mechanical durability can be advantageously used particularly for investigation of plant cells with hard walls. The paper deals with preparation of suitable optical probes based on coated fibre tapers and their using for local detection of extracellular pH in samples simulating native conditions of plant cells.Fibre tapers from single-mode and polymer-clad-silica fibres were prepared by tapering apparatus of own construction. The drawn tapers were immediately coated with a thin layer of Indium-Tin-Oxide in order to protect them from embrittlement. A CO_2 laser was used for cutting the tapered fibres in narrow taper waist. Opto-chemical transducer 2',7'-Bis(2-carbonylethyl)-5(6)-carboxyfluorescein was immobilized onto the end-face of cut fibre tapers by a thin TEOS layer. The pH was determined by fluorescence spectroscopy using excitation wavelength 473 nm.The fibre taper probes of waist diameter from 80 μm to 2 μm and of suitable optical and mechanical properties were prepared. Suitability of opto-chemical transducer 2',7'-Bis(2-carbonylethyl)-5(6)-carboxyfiuorescein for detection of samples simulating native conditions of pH ranging from 5.0 to 7.0 was confirmed. This approach has allowed us to determine extra-cellular pH of in-vitro samples.