Recent Progress and Perspectives on Non-Invasive Glucose Sensors

Abstract

Self-monitoring of blood glucose forms an important part of the management of diabetes and the prevention of hyperglycaemia and hypoglycaemia. Current glucose monitoring methods either use needle-prick enzymatic glucose-meters or subcutaneous continuous glucose sensors (CGM) and thus, non-invasive glucose measurements could greatly improve the self-management of diabetes. A wide range of non-invasive sensing techniques have been reported, though achieving a level of precision comparable to invasive meters remains a challenge. Optical sensors, which utilise the interactions between glucose and light, offer the potential for non-invasive continuous sensing, allowing real-time monitoring of glucose levels, and a range of different optical sensing technologies have been proposed. These are primarily based upon optical absorption and scattering effects and include infrared spectroscopy, Raman spectroscopy and optical coherence tomography (OCT), with other optical techniques such as photoacoustic spectroscopy (PAS) and polarimetry also reported. This review aims to discuss the current progress behind the most reported optical glucose sensing methods, theory and current limitations of optical sensing methods and the future technology development required to achieve an accurate optical-based glucose monitoring device.

Quantitative measurement of blood glucose influenced by multiple factors via photoacoustic technique combined with optimized wavelet neural networks

“…From Figure 4I, it can be found that the timeresolved PA signals of blood glucose shift towards right with the increase of detection distance, which is the same as the ultrasonic theory, that is, for the same specimens, the propagation time of ultrasonic wave is positively proportional to the detection distance. At the same time, from Figure 4J, the PA PPVs decreases with the increase of detection distance, which is also the same as the PA theory given in Equation (1), that is, the PA intensity is negatively proportional to the detection distance (r). Then, the PA detection experiments of blood glucose under the combination influence of five factors.…”

“…The PA amplitude of blood glucose increases with the laser energy. The PA PPVs of blood glucose linearly increase with the laser energies, which is identical to the PA theory given in Equation (1), that is, the PA intensity is positively proportional to the irradiation energy. In Figure 4C,D, the time-resolved PA signals and PPVs for different concentrations of blood glucose were obtained.…”

“…Conversely, when the value of c 2 is larger, the global searching capability of particles will be stronger but the local searching capability of particles will be weaken, which will impact the accuracy of choosing the optimal solution. To better determine the values of two acceleration factors (c 1 and c 2 ), based on the previous experience used by other researchers [39], the value of c 2 was set to 2 and the inertia weight factor (w) was set to a moderate value, that is, w = 0.6, then, the optimal value of c 1 was chosen in range of [1,2]. The effect of acceleration factor (c 1 ) on the MSE of predicting BGC influenced by multiple factors was studied, which is shown in Figure 7A.…”

“…From Figure 7A, it can be seen that the MSE is smallest when c 1 is 2, the MSE is 0.72 mmol/L. Then, when c 1 was determined to 2 and the inertia weight factor (w) was set to 0.6, the optimal value of c 2 was determined in range of [1,2]. The effect of acceleration factor (c 2 ) on the MSE of predicting BGC influenced by multiple factors was also studied, which is shown in Figure 7B.…”

“…It not only combines the advantages of pure optic and pure ultrasonic, but also has more precision and stability than those of other optical methods due to the detected ultrasonic signals rather than the photons. The blood glucose monitoring based on PA technology has already attracted more and more attention in recent years [1,2]. Mackenzie et al [3] used Nd:YAG pulsed laser as the excitation source to study the PA detection of blood glucose.…”