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Novel examples of optical sensors for micro-respirometry Michaella Roisin Watson (24304478) PUREID: 666964544 optical sensor 3D-printed indicator oxygen indicator ammonia indicator mircro-repirometry TVC bacteria urease smart dressing wound monitoring Microbial contamination and its detection are of critical importance across healthcare, biotechnology, food safety, and environmental sectors. Conventional culture-based methods for detecting contamination and monitoring bacterial growth are slow, labour-intensive, invasive, and unsuitable for continuous or real-time monitoring. As a result, there is a growing need for rapid, non-invasive, and user-friendly approaches capable of providing real-time information on microbial activity and its impact on surrounding environments. This thesis investigates the development of optical indicators based on luminescent and colourimetric sensing technologies for monitoring bacterial growth through key respiratory gases, namely oxygen (O₂) consumption and ammonia (NH₃) production.<br><br>In Chapter 3, a solid-state micro-respirometry (SS-μR) system incorporating a 3D-printed luminescent O₂ indicator was developed as a low-cost alternative to liquid-based micro-respirometry and conventional plate counting. The system enables quantification of total viable counts of aerobic bacteria and is validated using multiple clinically relevant species. Its performance was shown to be comparable to commercial systems while offering advantages in scalability, simplicity, and applicability to solid samples. Chapter 4 builds on this sensing system through integration of the O₂ indicator into a commercial occlusive wound dressing, creating a non-invasive smart wound monitoring system. Using agar-based and porcine skin wound models, the system successfully identifies critical bacterial colonisation thresholds associated with infection highlighting its potential as an early warning indicator of infection. <br><br>Chapters 5 and 6 describe the development of simple, low-cost colourimetric NH₃ indicators for monitoring bacterial growth and ureolytic activity in solid wound models and liquid cultures. Quantitative analysis is achieved using digital colour analysis, under aerobic and anaerobic conditions. Overall, this work demonstrates the versatility of optical gas-sensing indicators for real-time, non-invasive monitoring of microbial growth, with applications in diagnostics, environmental monitoring, and smart wound care. 2026-10-01T16:09:56Z Text Thesis 10.17034/32826209.v1 https://figshare.com/articles/thesis/Novel_examples_of_optical_sensors_for_micro-respirometry/32826209 All Rights Reserved