Extended Near-Infrared Optoacoustic Spectrometry for Sensing Physiological Concentrations of Glucose

Abstract

Glucose sensing is pursued extensively in biomedical research and clinical practice for assessment of the carbohydrate and fat metabolism as well as in the context of an array of disorders, including diabetes, morbid obesity, and cancer. Currently used methods for real-time glucose measurements are invasive and require access to body fluids, with novel tools and methods for non-invasive sensing of the glucose levels highly desired. In this study, we introduce a near-infrared (NIR) optoacoustic spectrometer for sensing physiological concentrations of glucose within aqueous media and describe the glucose spectra within 850–1,900 nm and various concentration ranges. We apply the ratiometric and dictionary learning methods with a training set of data and validate their utility for glucose concentration measurements with optoacoustics in the probe dataset. We demonstrate the superior signal-to-noise ratio (factor of ~3.9) achieved with dictionary learning over the ratiometric approach across the wide glucose concentration range. Our data show a linear relationship between the optoacoustic signal intensity and physiological glucose concentration, in line with the results of optical spectroscopy. Thus, the feasibility of detecting physiological glucose concentrations using NIR optoacoustic spectroscopy is demonstrated, enabling the sensing glucose with ±10 mg/dl precision.

Emerging Technologies to Image Tissue Metabolism

“…As an alternative to the use of labels, it has also been shown that optoacoustic measurements can non-invasively capture glucose label free when combined with the chemical specificity of near-infrared or mid-infrared spectroscopy (Ghazaryan et al, 2018;Pleitez et al, 2013). Although these studies relied on single-point measurements, they indicate imaging potential, as recently demonstrated in vivo in human skin (Sim et al, 2018) ( Figures 1I and 1J).…”

Optoacoustic imaging of GLP-1 Receptor with a near-infrared exendin-4 analog

“…Compared to traditional fluorescence imaging systems, the key difference of MSOT is that its ability to use light for excitation and sound for detection enables a greater penetration depth. The development of optoacoustic imaging tools for diabetes is a valuable but unmet clinical need 7,8,25,31,43 . A handful of proof-of-concept studies in the literature have emerged to show the potential of diabetes monitoring via optoacoustic imaging, but none feature direct visualizations of ß-cells 6-9, 19, 44-46 .…”

“…Recent studies typically demonstrated an indirect biological response to the symptoms of diabetes via vasculature tracking 44,47 , diabetic neuropathy 48 or glucose sensing 8,45,46 .…”

Towards accurate and label-free monitoring of bio-analytes using supercontinuum based multispectral photoacoustic spectroscopy in the extended near-infrared wavelength regime

“…Therefore, established non-invasive monitoring techniques are mostly based on commercially available monochromatic laser systems in extended-NIR [9][10][11] . However, since the absorption of glucose has similar characteristics to that of other bio-analytes (like water and cholesterol), the monochromatic based monitoring techniques have limited sensitivity [12][13][14][15][16] . SC lasers offer an attractive all-fiber alternative to generate broadband emission from ultra violet (UV) to mid infrared region (MIR) of electromagnetic spectrum [17][18][19] .…”