Non-invasive monitoring of glucose and lactate in humans by reverse iontophoresis
Blood glucose and lactate monitoring are beneficial to many patients, e. g. diabetes mellitus patients, critical care patients, etc. However, there are very few noninvasive or continuous monitoring systems for these parameters and significant clinical benefit could be achieved if such systems were readily available. Therefore, this study focused on the development of a prototype monitoring system for non-invasive monitoring of blood glucose and lactate in human subjects. The current study consisted of three parts. In the first part of the study, in vitro experiments were performed using a model system for the optimisation of glucose and lactate extraction by reverse iontophoresis. In the second part of the study, a portable and programmable constant current device for iontophoresis was designed, developed and evaluated. This newly-developed device was then used in the final part of the study. In the third part of the study, screen-printed silver-silver chloride electrodes were fabricated and studied. Finally, the newly-developed device and electrodes were then used on healthy volunteers to study long duration bipolar direct current iontophoresis effects on transdermal glucose and lactate extraction and on the electrical properties of human skin. Importantly, the results show that reverse iontophoresis extraction of glucose and lactate needs careful optimisation of extraction times and current waveforms. In addition, significant temporary changes in skin impedance occurred as a result of reverse iontophoresis. These impedance changes show promise for their use in the calibration of iontophoresis devices for human use.