Medical examinations rely increasingly also on in vitro diagnostics to identify and monitor diseases. Especially for patients with chronic health conditions and for the detection of highly infectious diseases, point-of-care diagnostics are a desired tool. The vision is to enable the detection of diagnostic markers directly from a blood sample within a reasonably short time frame and without any complex sample handling so that the test can be performed by untrained users. Different health conditions can be diagnosed with a vast range of diagnostic markers: blood gases, electrolytes, metabolites, hormones, antibodies, and cells. Ideally a single point-of-care device should be able to measure each of these markers. Electrochemical sensors are praised for their high sensitivity and easy integration into digital handheld devices for medical diagnostics since their development in the mid of the 20th century. However, currently only the well-established blood glucose sensor can be considered to fulfil the above-mentioned requirements for a quantitative point-of-care test. This work addresses some of the challenges that currently prevent electrochemical sensors from becoming the standard biosensor platforms: low signals due to the low charge-to-size ratio of most diagnostic markers, the screening of those charges by the high concentration of dissolved ions in physiological samples, and interfering signals from the complex sample such as whole blood. Three different techniques are applied to detect several diagnostic markers directly from whole blood. Dissolved blood oxygen is measured in a Clark-type set-up by amperometry, the portion of red blood cells in blood by electrochemical impedance spectroscopy and thyroid-stimulating hormone via extended-gate field-effect transistors. All three assays are developed to allow transfer into mass-producible devices that can operate at the point-of-care.weiterlesen