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Time-Resolved Spectroscopy of Fluorescence Quenching in Optical Fibre-Based pH Sensors

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Scottish Universities Physics Alliance (SUPA), Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK
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EPSRC Proteus IRC Hub, Centre for Inflammation Research, Queen’s Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK
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Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering & Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK
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School of Chemistry, EaStChem, University of Edinburgh, Joseph Black Building, West Mains Road, Edinburgh EH9 3FF, UK
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Centre for Photonics and Photonic Materials, University of Bath, Claverton Down, Bath BA27AY, UK
*
Author to whom correspondence should be addressed.
Current address: Centre for Inflammation Research, Queen’s Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, UK.
Current address: The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Midlothian EH25 9RG, UK.
§
Current address: Department of Analytical Chemistry, Faculty of Pharmacy, Izmir Katip Celebi University, 35620 Izmir, Turkey.
Current address: Optoelectronics Research Centre, University of Southampton, University Road, Southampton SO17 1BJ, UK.
Current address: Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China.
Sensors 2020, 20(21), 6115; https://doi.org/10.3390/s20216115
Received: 10 September 2020 / Revised: 13 October 2020 / Accepted: 20 October 2020 / Published: 27 October 2020
(This article belongs to the Section Biomedical Sensors)
Numerous optodes, with fluorophores as the chemical sensing element and optical fibres for light delivery and collection, have been fabricated for minimally invasive endoscopic measurements of key physiological parameters such as pH. These flexible miniaturised optodes have typically attempted to maximize signal-to-noise through the application of high concentrations of fluorophores. We show that high-density attachment of carboxyfluorescein onto silica microspheres, the sensing elements, results in fluorescence energy transfer, manifesting as reduced fluorescence intensity and lifetime in addition to spectral changes. We demonstrate that the change in fluorescence intensity of carboxyfluorescein with pH in this “high-density” regime is opposite to that normally observed, with complex variations in fluorescent lifetime across the emission spectra of coupled fluorophores. Improved understanding of such highly loaded sensor beads is important because it leads to large increases in photostability and will aid the development of compact fibre probes, suitable for clinical applications. The time-resolved spectral measurement techniques presented here can be further applied to similar studies of other optodes. View Full-Text
Keywords: fluorescence spectroscopy; time-resolved spectroscopy; optical fibre sensing; biological sensor fluorescence spectroscopy; time-resolved spectroscopy; optical fibre sensing; biological sensor
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MDPI and ACS Style

Ehrlich, K.; Choudhary, T.R.; Ucuncu, M.; Megia-Fernandez, A.; Harrington, K.; Wood, H.A.C.; Yu, F.; Choudhury, D.; Dhaliwal, K.; Bradley, M.; Tanner, M.G. Time-Resolved Spectroscopy of Fluorescence Quenching in Optical Fibre-Based pH Sensors. Sensors 2020, 20, 6115. https://doi.org/10.3390/s20216115

AMA Style

Ehrlich K, Choudhary TR, Ucuncu M, Megia-Fernandez A, Harrington K, Wood HAC, Yu F, Choudhury D, Dhaliwal K, Bradley M, Tanner MG. Time-Resolved Spectroscopy of Fluorescence Quenching in Optical Fibre-Based pH Sensors. Sensors. 2020; 20(21):6115. https://doi.org/10.3390/s20216115

Chicago/Turabian Style

Ehrlich, Katjana, Tushar R. Choudhary, Muhammed Ucuncu, Alicia Megia-Fernandez, Kerrianne Harrington, Harry A.C. Wood, Fei Yu, Debaditya Choudhury, Kev Dhaliwal, Mark Bradley, and Michael G. Tanner 2020. "Time-Resolved Spectroscopy of Fluorescence Quenching in Optical Fibre-Based pH Sensors" Sensors 20, no. 21: 6115. https://doi.org/10.3390/s20216115

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