Biomed. Opt. Express 3, 667–680 (2012)
Diabetes is a widespread disease that affects 346 million people around the world and causes an estimated 3.4 million deaths every year. Although glucose levels can be measured through invasive procedures such as polarimetry, Raman spectroscopy and photoacoustic spectroscopy, scientists have so far been unsuccessful in realizing a reliable non-invasive alternative monitoring technique. Markus Sigrist and colleagues in Switzerland have now developed a mid-infrared photoacoustic technique that can be used to track glucose by analysing deep epidermal layers in the skin. Their set-up comprises an external-cavity quantum cascade laser (tuning range of 1,010–1,095 cm−1) and a 78 mm3 photoacoustic cell for detection. They controlled the glucose levels of epidermal skin samples housed in the photoacoustic cell by introducing aqueous glucose solutions of different concentrations in the range of 1–100 g l−1. The detection limit of this technique is around 1 g l−1, which, although within the physiological range of 0.3–5 g l−1, is still too high for the in vivo glucose monitoring of diabetes patients. The researchers say that a lower detection limit could be achieved by placing the sensor directly on human skin, which would provide a rigid seal for the photoacoustic cell.
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