A simple near infrared spectroscopy system for quantification of glucose in solution and intralipid samples

Davison, Nicholas (2023) A simple near infrared spectroscopy system for quantification of glucose in solution and intralipid samples. In: 21st International Conference on Near Infrared Spectroscopy, 2023-07-20 - 2024-07-24, PCO Tyrol Congress Centre, Innsbruck, Tyrol, Austria. (Unpublished)

Abstract

Near Infrared (NIR) spectroscopy offers several potential applications in the field of biosensing due to the depth of penetration of NIR radiation in tissue compared to other spectral regions. Glucose sensing is a regular part of the management of diabetes, but current monitoring is performed using invasive needle-prick methods or subcutaneous sensors. A non-invasive, continuous glucose sensing device could benefit patients in the self-management of the condition. However, sensing accuracy depends heavily on the design and choice of components for the system. We aimed to develop a NIR absorption spectroscopy system capable of determining liquid glucose concentrations in the physiological range, using simple NIR detectors and light sources. Two different light sources (a halogen lamp and a globar) and three NIR detector assemblies (a photodiode array, a Czerny-Turner monochromator with an InGaAs photodiode and a miniature Fourier Transform infrared spectrometer) were systematically tested by collecting spectra from the same set of aqueous glucose concentrations, from 10-100mmol/L in 10mmol/L increments. Partial Least Squares (PLS) regression was used to determine the Standard Error of Prediction (SEP) and coefficient of determination (R2), which were compared for each component. The optimal system was determined to be the halogen lamp with the InGaAs photodiode and further concentrations with decreasing concentration step were tested to identify the limit of detection, which was determined to be 2mmol/L. Finally, normally reflected light was collected from glucose samples in 10% intralipid suspension from 2-10mmol/L. The relationship between intensity and concentration indicated that below 1300nm the spectra were dominated by scattering, which varied with glucose concentration as predicted by Mie theory, whilst above 1300nm the spectra were dominated by absorption. In intralipid, the data showed an SEP of 3.15mmol/L, and this suggests that the system offers potential to collect reflectance spectra from more advanced intralipid-based tissue phantoms and form the basis for a prototype NIR glucose-sensing device.