Non-invasive glucose measurements in humans with time-gated mid-IR optoacoustic spectroscopy

Frequent measurements of blood sugar are essential for the management of diabetes. While finger pricking offers accurate measurements of blood glucose, it is a procedure that causes discomfort and risk of infection. Conversely, minimally invasive biochemical sensors based on micro-needles do not assess glucose in blood but in the interstitial fluid. While most optical sensors also detect in bulk from the interstitial fluid, a depth-gated mid-infrared optoacoustic sensor (DIROS) was recently proposed to non-invasively detect glucose concentrations in blood by means of time-gating. While DIROS was previously demonstrated only in animals, herein we present the first pilot investigation of the sensor in humans, based on a multivariate model fit to measurement data obtained from healthy volunteers (n=5) during an oral glucose tolerance test. By time-gating optoacoustic signals, i.e. selecting time points corresponding to different depths within the skin based on the ultrasound time-of-flight, we confirm in humans an improved measurement accuracy when targeting deeper skin layers, which are rich in vasculature. The results set the first milestone towards depth-dependent in-blood glucose detection in humans and highlight potential for DIROS in clinical application.