Technology developed to measure pH in lung alveoli
January 2017: Team develops a new miniaturised technology to sense areas of the lung that have never been explored before
The lungs are responsible for exchanging oxygen for carbon dioxide, a job performed by delicate grape like structures within the lung known as alveoli. Each alveolus is absolutely tiny but there are so many of them that if they were rolled out flat they would equal the surface area of a whole tennis court, and this size helps them do their job effectively. In many lung diseases bacteria and inflammatory cells gain access to the alveoli and the ability to get oxygen in and out is compromised. Scientists concentrate major effort to model lung disease and biology but our knowledge of these tiny structures has been limited to biopsy samples or post-mortem samples, and we know that lung tissue behaves differently when taken away from the lungs to be examined in the lab. Measurements and investigations taken within the alveoli without removing them has been limited by the tiny scale involved and the accessibility of this part of the lung in life. One particularly important measurement is the pH (or acidity) in the fluid in these alveoli as this can affect cell function, antibiotic action and also be an indicator about the health of the lung.
A multidisciplinary team composed of physicists, chemists, mathematicians and biomedical researchers based at the Center for Inflammation Research has developed a first-in-class technology to allow the measurement of pH in the alveoli. They developed and tested a device that could reliably measure alveolar pH in a serial fashion, overcoming many prohibitive physical challenges. The device featured a bespoke optical fibre (the optical analogue of wires), comprising separate channels (fibre cores) to send/receive light to/from the alveolar environment. This allowed the team to accurately and reliably monitor the colours of light emitted by sensors imprinted at the end of the fibre and measure any changes that occur in response to variations in alveolar pH. The team used sophisticated laser micromachining technology to develop a tiny, made-to-measure glass component to package this optical fibre into a robust, clinically deployable probe. They also devised mathematical methods to evaluate pH values accurately from the measured changes in the colour of light emitted by the pH sensors.
The team showed the sensitivity in fluids followed by a whole lung model that was human-sized, demonstrating that tiny but significant changes in pH could be measured. The technology is flexible to enable other sensors to be added to the system and the team is now aiming to perform pH sensing in human lungs in 2017.
The project, funded by the Engineering and Physical Sciences Research Council is published in the journal Biomedical Optics Express.
Choudhury, D, Tanner, MG, Mcaughtrie, S, Yu, F, Mills, B, Choudhary, TR, Seth, S, Craven, TH, Stone, JM, Mati, IK, Campbell, CJ, Bradley, M, Williams, CKI, Dhaliwal, K, Birks, TA & Thomson, RR 2016, 'Endoscopic sensing of alveolar pH' Biomedical Optics Express, vol 8, no. 1, pp. 243-259 (2017)
Digital Object Identifier (DOI): 10.1364/BOE.8.000243
Published paper in Biomedical Optics Express (OSA Publishing website)