Analysis of biologically important compounds is performed with clinical, forensic, toxicological, pharmacological, and research contexts. A considerable amount of research has been performed in recent years in order to improve the present analytical methods or introduce new methods for rapid, sensitive, and accurate determination of biologically important compounds. Direct and label-free analytical method for the biological compounds is of great importance due to faster analysis time, lower limit of detection, and the need for smaller sample volumes. In the recent years, electrochemical sensors and biosensors have become more preferable due to their low cost, portability, miniaturization possibility, flexibility, and sensitivity. In addition to these characteristics, biomolecules (antibody and aptamers) immobilized onto the surface of electrochemical conductive biosensing platforms provide high specificity for detecting of target analytes. Impedimetric sensors and biosensors were prepared and used for the direct and label-free determination of botulinum neurotoxin serotype A, cocaine, ampyra and non- Hodgkin’s lymphoma (NHL) cancer cells. The sensing probes were prepared by the proper electrodes. The modification steps were followed by electrochemical, spectroscopic and microscopic methods. The modified electrodes were used to determine the target analytes in real samples with satisfactory results
