REVERSE IONTOPHORESIS - DEVELOPMENT OF A NONINVASIVE APPROACH FOR GLUCOSE MONITORING

Solvent flow generated during iontophoresis can be used to convect neu tral molecules through the skin, thereby greatly enhancing their flux. This concept was exploited to realize noninvasive glucose measurement by its iontophoretic extraction from the subcutaneous tissue. The hyp othesis was tested in vitro using hairless mouse skin. The dermal surf ace was bathed with a glucose solution; chambers on the epidermal surf ace housed the current delivery electrodes. Iontophoresis (at 0.36 mA/ cm2) was performed for 2 hr, at the end of which the solutions in cont act with the electrodes were analyzed. The amount extracted was propor tional to the glucose solution concentration bathing the dermis. Highe r radioactivity levels were found at the anode than at the cathode, po ssibly because of glucose metabolism during its outward transport acro ss the skin. Glucose biotransformation results in negatively charged m etabolites which migrate to the anode. Two sensitive glucose sensors w ere developed; one was selective for glucose, the other for glucose an d related compounds. Both sensors indicated the presence of glucose at the cathode but an abnormally high value was also recorded at the ano de. This signal, however, was not due to glucose but rather to electro active ascorbate withdrawn from the skin. Finally, a system has been d eveloped with which glucose can be extracted noninvasively from the su bcutaneous tissue and unambiguously measured. Whether iontophoretic gl ucose sampling in vivo will be equally successful remains to be answer ed.