Development of affinity biosensors based on electrochemical impedance spectroscopy for determination of insulin and insulin antibodies

The detection of insülin level in blood is of great importance for clinical diagnostics, because it serves as a predictor of diabetes and insulinoma. Diabetes mellitus is the most common endocrine diseases in worldwide. It is a chronic disease in abnormalities of carbohydrates, protein and fat metabolism, and characterized by their associated clinical and biochemical findings. Insulin antibodies (IA) are often seen in patients undergoing insulin treatment. These antibodies, however, do not cause hyperglycemia or hypoglycemia. These antibodies almost never bind to insulin (low capacity), or, if they do bind to insulin, they never separate (high affinity). The latter typemay trigger increased insulin resistance, but they never induce hypoglycemia. On the other hand, a disease that is known to induce hypoglycemia by producing insulin antibodies to endogenous insulin, despite never having received insulin injections, is insulin autoimmune syndrome (IAS). The antibodies seen in this disease have lower affinity and higher capacity than non-IAS antibodies. These antibodies readily bind to insulin, and are difficult to separate from it. In this thesis, two different biosensors were developed for the determination of insulin and insulin antibodies amount. For this purpose it was used the biosensors utilizing Electrochemical Impedance Spectroscopy (EIS) for analyzing of the compounds that hasn't a catalytic reaction activity such as insulin and insulin antibodies. For biosensors, several optimization studies were carried out. After optimization studies, characterization studies of biosensors were realized.