We present a toolkit for a multiplexed pH and oxygen sensing probe in the distal lung using multicore fibres. Measuring physiological relevant parameters like pH and oxygen is of significant importance in understanding changes associated with disease pathology. We present here, a single multicore fibre based pH and oxygen sensing probe which can be used with a standard bronchoscope to perform in vivo measurements in the distal lung.
The multiplexed probe consists of fluorescent pH sensors (fluorescein based) and oxygen sensors (Palladium porphyrin complex based) covalently bonded to silica microspheres (10 µm) loaded on the distal facet of a 19 core (10 µm core diameter) multicore fibre (total diameter of ~150 µm excluding coating). Pits are formed by selectively etching the cores using hydrofluoric acid, multiplexing is achieved through the self-location of individual probes on differing cores. This architecture can be expanded to include probes for further parameters. Robust measurements are demonstrated of self-referencing fluorophores, not limited by photobleaching, with short (100ms) measurement times at low (~10µW) illumination powers.
We have performed on bench calibration and tests of in vitro tissue models and in an ovine whole lung model to validate our sensors. The pH sensor is demonstrated in the physiologically relevant range of pH 5 to pH 8.5 and with an accuracy of ± 0.05 pH units. The oxygen sensor is demonstrated in gas mixtures downwards from 20% oxygen and in liquid saturated with 20% oxygen mixtures (~8mg/L) down to full depletion (0mg/L) with ~0.5mg/L accuracy.
Tushar R. Choudhary, Michael G. Tanner, Alicia Megia-Fernandez, Kerrianne Harrington, Harry A. Wood, Sunay Chankeshwara, Patricia Zhu, Debaditya Choudhury, Fei Yu, Robert R. Thomson, Rory R. Duncan, Kevin Dhaliwal, and Mark Bradley, "Multiplexed fibre optic sensing in the distal lung (Conference Presentation)," Proc. SPIE 10058, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XVII, 100580E (Presented at SPIE BiOS: January 28, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2249982.5371911252001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon