The invention relates to ex-situ biosensors that impedimetrically detect cardiac biomarkers of interest in a bodily fluid sample derived from a patient. The biosensors include a multi-array of vertically aligned platinum wires having immobilized thereon an aptamer that is selected to specifically and selectively bind to the cardiac markers of interest. The biosensors are contacted with a portion of the bodily fluid sample, and the aptamer binds to the cardiac markers of interest in the bodily fluid sample. As a result, an electrochemical impedance signal is generated and therefore, a change in electrochemical impedance is indicative of the presence of the cardiac markers of interest in the bodily fluid sample. The biosensors are point-of-care, on-demand devices that can be used in a medical environment, as well as in domestic settings.