Immunosensors use antigen-antibody interactions [1, 2] to detect a wide range of analytes of great interest in medical diagnostics, environmental analysis and forensics [3, 4 ], including pathogens [5], drugs [6], bacteria [7], toxins [8], and biomarkers [9]. Overall, immunosensors use the same chemical approach as early immunoassays, but offer faster and simpler analytical procedures that can be conducted at the point of care [10]. Immunosensors use an immobilized antibody as a transducer. The antigen-antibody binding event results in electrical or optical changes. The interaction of the antigen with the immobilized antibody can be monitored using different detection methods. In this context, electrochemical immunosensors are increasingly used for biosensing applications [11]. Electrochemical impedance spectroscopy (EIS) is an electrochemical technique, which facilitates label-free detection [12, 13], thus offering significant advantages in terms of simplicity and rapidity compared to conventional immunosensing processes. Immobilization of an antibody on the transducer element is a crucial step in the preparation of immunosensors [14] [15]. Physical adsorption is the simplest immobilization method, but suffers from random antibody orientation and poor reproducibility [16–18]. Approximately 90% of antibodies have an inactive orientation, due to steric blocking of antigen binding sites on these antibodies [12, 19]. A more stable and reproducible antibody binding is achieved by covalent attachment, but this attachment must ensure that antigen binding sites are kept free [20]. For this purpose, the coupling of antibodies with the G/A protein was used [21]. A simpler and more effective method for Ab...... middle of paper...... urine of a pregnant woman, with a pregnancy of 3 to 5 weeks. The hCG concentration obtained was 3.5 ng/ml (17.4 mIU/ml), consistent with the pregnancy status. Insert Figure 5 here 4. ConclusionsIn summary, a new impedimetric biosensor has been developed for the determination of hCG in urine. A simple approach to generate an aminated graphene surface that is presented with an antibody bond in a suitable orientation for antigen binding. The observed resistance to electron transfer increased linearly with increasing log(hCG) concentration. The sensor response was not affected by chemical components present in synthetic urine indicating non-specific binding. The sensor was successfully applied to quantitatively detect hCG in the urine of pregnant women, suggesting a successful application in point-of-care diagnostics in the near future. future.