Open Access

Miguel Ángel Pleitez Rafael

• This doctoral thesis is concerned with the development of a method that allows to measure in vivo and non-invasively the mid-infrared absorption spectra of human epidermis, using photoacoustic spectroscopy. The main focus is the monitoring of the glucose level in epidermal interstitial fluid and its correlation with the blood glucose level; which is the most important parameter for the diagnosis and treatment of diabetes mellitus. Most publications in this field have only reported measurements in vitro for the absorption spectra of epidermis in the mid-infrared range. Using the approach presented in this work, it was possible to record in vivo and in situ the absorption spectra of skin of volunteers; and with these spectra, the changing glucose concentration could be monitored. The novelty of the photoacoustic method introduced here is that it operates in acoustic resonance in the ultrasound range. This considerably reduces the signal noise due to the external acoustic background. Although the photoacoustic method reported in this work was used to measure glucose in human epidermis, it can also be applied to other solid samples with relevant absorption bands in the mid-infrared. Furthermore, it can be used in other spectral regions if the laser source covers relevant absorption bands of the sample.