Novel single-wall carbon nanotube screen-printed electrode as an immunosensor for human chorionic gonadotropin

Human chorionic gonadotropin (hCG) is a key diagnostic marker of pregnancy. A sensor device for detection of hCG has been fabricated using a CNT (carbon nanotube) screen printed electrode (SPE). The CNT working electrode was first electrochemically oxidised to yield a hydroxyl terminated surface, which was subsequently silanized to produce an amine terminated CNT. The aminated surface allowed oriented binding of an antibody (Ab) bioreceptor, targeted against hCG (anti-hCG), to the CNT-SPE. This was achieved by activating the –COOH group at the Fc terminal of the antibody and incubating the SPE-CNT-NH2 electrode in the activated Ab solution.Electrochemical Impedance Spectroscopy (EIS) and Raman Spectrometry with Confocal Microscopy studies were performed at each stage of the chemical modification process in order to confirm the resulting surface changes associated with each functionalization process.The SPE-CNT-NH2-Ab devices displayed linear responses to hCG in EIS assays in the concentration range from 0.01 × 10−9 g cm−3 to 100 × 10−9 g cm−3. High specificity was observed with respect to hCG detected in solutions containing urine components–these components producing a negligible change in the sensor readout relative to changes induced by hCG. Successful hCG detection was also achieved using real urine samples from pregnant woman.Overall, the immunosensor developed is a promising tool for detecting hCG in a point-of-care diagnostic (POC), due to the excellent detection capability, simplicity of fabrication, low cost, high sensitivity and selectivity.