A new noninvasive approach to blood glucose monitoring uses photoacoustic spectroscopy (PAS): a painless pulse of laser light, applied externally to the skin, is absorbed by glucose molecules and creates a measurable sound signature that reads sugar levels in the fluid in and under skin cells in seconds.
The approach was devised by researchers at Biophysics Institute at the University of Frankfurt (Germany).1 Data showing the skin cell glucose levels at one-hundredth of a millimeter beneath the skin is related to blood glucose levels, said lead researcher Werner Mäntele, Ph.D., but previous attempts to use PAS in this manner have been hampered by distortion related to changes of air pressure, temperature, and humidity caused by the contact with living skin.
To overcome these constraints, the team used an open, windowless cavity architecture tuned for optimum performance in the ultrasound range between 50 and 60 kHz. In combination with an external cavity tunable quantum cascade laser emitting from ~1000 to 1245 cm-1, the approach enables a high signal-to-noise-ratio (SNR) for mid-infrared (mid-IR) spectra of human skin. This facilitates measurement in situ the absorption spectrum of human epidermis in the mid-IR region at high SNR in just a few seconds. While the design is still experimental and would have to be tested and approved by regulatory agencies before becoming commercially available, the team continues to refine it. In a close collaboration with an industry partner (Elte Sensoric; Gelnhausen, Germany), they expect to have a small shoebox-sized device ready in three years, followed by a portable glucometer.
1. M. A. Pleitez et al., Rev. Sci. Instrum., 84, 084901 (2013); http://dx.doi.org/10.1063/1.4816723.
