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Download?Doi=10.1.1.496.1139&Rep=Rep1&Type=Pdf City Research Online City, University of London Institutional Repository Citation: Baishya, N. (2020). In-vitro and In-vivo spectrometric investigations on the behavior oflactate under conditions emulating septic shock. (Unpublished Doctoral thesis, City, University of London) This is the accepted version of the paper. This version of the publication may differ from the final published version. Permanent repository link: https://openaccess.city.ac.uk/id/eprint/25371/ Link to published version: Copyright: City Research Online aims to make research outputs of City, University of London available to a wider audience. Copyright and Moral Rights remain with the author(s) and/or copyright holders. URLs from City Research Online may be freely distributed and linked to. Reuse: Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. City Research Online: http://openaccess.city.ac.uk/ [email protected] In-vitro and In-vivo spectrometric investigations on the behavior of lactate under conditions emulating septic shock Nystha Baishya Supervisor: Professor Panicos Kyriacou Research Centre for Biomedical Engineering This dissertation is submitted for the degree of Doctor of Philosophy City, University of London September 2020 Dedicated to all the healthcare professionals involved in the COVID- 19 pandemic. Abstract Lactate is an inter- and intra-cellular product in the human body. In patients with life threatening illnesses, the secretion and excretion of lactate is impaired, which might cause the pH of blood to shift to be either acidic or basic. Lactic acidosis can be regarded as a useful biomarker for the onset of haemodynamic shock in patients. Lactate concen- tration levels are measured and monitored frequently in critical care by utilizing invasive blood sampling techniques. Such techniques, apart from their invasive nature, which is not desirable, are intermittent, time consuming and do not allow the continuous moni- toring of lactate. Hence, there is a need for new innovative approaches in research which could lead to the development of non-invasive and continuous monitoring technologies for lactate. The motivation of this research is to explore rigorously the capability and potential of absorption spectroscopy as a technique which could enable the development of non-invasive lactate sensors. The focus of the research lies in unravelling the basic light-lactate molecular interac- tions in different media, both in-vitro and in-vivo, utilizing a wide range of spectrometers. The research investigated lactate “signature peaks” in solution samples, including differ- ent concentrations of lactate, in various media (buffer, human serum and whole blood) across the UltraViolet (UV), Visible (Vis), Near Infrared (NIR) and Mid Infrared (MIR) parts of the EM. The results have shown that lactate has limited presence in the UV and Vis parts of the EM spectrum. For the first time, ’signature peaks’ for lactate in the NIR and MIR spectral regions have been identified, suggesting that these spectral regions could be used for lactate concentration predictions with 90 % accuracy. More uniquely, it has been shown that these ’signature peaks’ for lactate in the NIR spectral region are influenced by the change in physiological conditions and media; theseare therefore, not consistent. Nevertheless, in the ’fingerprint region’ of the MIR spectral region, these ’signature peaks’ for lactate are not only consistent but they could be used inter changeably for different physiological conditions and media for lactate concentra- tion prediction. The results from this suggests that the ’fingerprint region’ of the MIR spectral region is most preferred for lactate concentration determination in-vitro, for accuracy needed in critical care. Despite being the most preferred spectral region, the major disadvantage of MIR is the penetration depth and hence, it might not be suitable for in-vivo lactate measure- ments in blood through skin. Therefore, a pilot in-vivo study utilizing, a portable NIR spectrometer was conducted in order to evaluate the feasibility of measuring lactate con- centrations in this region. The results from this study have shown for the first time that the NIR region could be suitable for measuring lactate concentrations using Absorp- tion/Reflectance portable Spectroscopy accurately and non-invasively. The output from this research could pave the way for the development of optical sensing point-of-care technologies for the continuous and non-invasive monitoring of lactate in critical care. iii Table of contents Abstract iii Nomenclature xiii List of publications xix Declaration xxi 1 Introduction 1 1.1 Motivation ................................... 1 1.2 Aims and Objectives ............................. 3 1.3 Contribution (Novelty) ............................ 5 1.4 Thesis Structure ............................... 5 2 Lactate in the Human Body 8 2.1 Introduction .................................. 8 2.2 History of Lactate .............................. 9 2.3 Mechanisms of Lactate in the human body . 10 2.4 Lactate in Pathology ............................. 15 2.5 Hyperlactatemia as a Biomarker Marker for Haemodynamic Shock . 17 2.6 Lactate and Acidosis ............................. 23 2.7 Summary ................................... 27 3 Spectroscopy 28 3.1 Introduction .................................. 28 3.2 History and Principle ............................. 29 3.3 The Origin and Intensity of an Absorption Band . 38 3.4 Instrumentation ................................ 40 3.5 Spectral Collection and Visualization Software . 49 3.6 Data Analysis ................................. 49 3.7 Spectral Analysis ............................... 55 3.8 Summary ................................... 61 iv 4 Spectroscopy in Lactate Detection 62 4.1 Introduction .................................. 62 4.2 History .................................... 63 4.3 Current State-of-the-Art Lactate Sensing . 64 4.4 Current Commercial Devices ......................... 71 4.5 Non-Invasive Lactate Biosensors ....................... 76 4.6 Summary ................................... 87 5 In-vitro Spectrometric Analysis of Lactate in Buffer Solution 88 5.1 Introduction .................................. 88 5.2 Sample Preparation .............................. 89 5.3 Spectroscopy (UV/Vis, NIR and MIR) ................... 90 5.4 Data Analysis (UV/Vis, NIR and MIR) . 93 5.5 Results ..................................... 95 5.6 Summary ...................................106 6 In-vitro Spectrometric Analysis of Lactate in Buffer Solution of changing pH 108 6.1 Introduction ..................................108 6.2 Sample Preparation ..............................109 6.3 Lactate Concentration Measurements (Theoretical) . 111 6.4 Spectroscopy (UV/Vis, NIR and MIR) . 112 6.5 Data Analysis (UV/Vis, NIR and MIR) . 113 6.6 Results .....................................115 6.7 Summary ...................................124 7 In-vitro Spectrometric Analysis of Lactate in Human Serum 127 7.1 Introduction ..................................127 7.2 Sample Preparation ..............................128 7.3 Spectroscopy (Dual Beam Dispersive NIR, FTNIR and MIR) . 129 7.4 Data Analysis (Dual Beam Dispersive NIR, FTNIR and MIR) . 131 7.5 Results .....................................132 7.6 Summary ...................................136 8 In-vitro Spectrometric Analysis of Lactate in Whole Blood 138 8.1 Introduction ..................................138 8.2 Sample Preparation ..............................139 8.3 Spectroscopy (Dual Beam Dispersive NIR, FTNIR and MIR) . 140 8.4 Data Analysis (Dual Beam Dispersive NIR, FTNIR and MIR) . 141 8.5 Results .....................................142 8.6 Summary ...................................146 v 9 In-vivo Spectrometric Analysis of Lactate in Healthy Volunteers 147 9.1 Introduction ..................................147 9.2 Measurements set-up and protocols . 148 9.3 Reflectance Spectroscopy (NIR) . 151 9.4 Spectral Analysis (NIR) . 151 9.5 Results .....................................152 9.6 Summary ...................................155 10 Discussion 157 10.1 Introduction ..................................157 10.2 Discussion for Chapters 5 and 6 . 158 10.3 Discussions for Chapters 7 and 8 . 169 10.4 Discussions for Chapter 9 . 177 11 Conclusion and Future Scope of Work 180 11.1 Introduction ..................................180 11.2 Major Conclusions and Contributions . 181 11.3 Future Scope of Work ............................184 References 185 Appendix A Appendices 215 Appendix B Appendices 236 vi List of figures 2.1 Lactic Acid .................................. 9 2.2 Glycolytic Pathway .............................. 11 2.3 Aerobic Respiration Summary ........................ 12 2.4 Pyruvate to Lactate conversion ....................... 13 2.5 Cori’s Cycle .................................. 13 2.6 D and L lactate ................................ 14 2.7 Methylglyoxal pathway ............................ 16 3.1 Electromagnetic Spectrum .......................... 30 3.2 Allowed Electronic Transitions ........................ 31 3.3 Mechanical model of a vibrating diatomic molecule . 34 3.4 Fundamental modes of Vibrations in a molecule . 35 3.5 Anharmonic Oscillator Model .......................
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