Electrical detection method of protein concentration on ITO interdigitated electrodes

An electrical detection method of the concentration of the protein immobilizing on a biochip has been developed based on the indium tin oxide (ITO) interdigitated electrodes as the detection sites. The result of the protein concentration can be measured by a multimeter directly. The proposed protocol was to immobilize protein on the ITO interdigitated electrodes on a glass substrate. The immobilized protein was prepared to conjugate to biotin. Then, gold nanoparticles were bound to the protein through biotin-streptavidin linkage. Gold enhancement was performed for enlarging the gold nanoparticles. Therefore, a conductive layer was formed across the electrode gaps. The resistance values across the electrode can be measured by a multimeter directly. From the result, the concentrations of the immobilized protein between 5 and 1000 ng/ml can be represented by the resistance values quantitatively. The proposed detection method is simplicity, low cost, and miniaturization, therefore, it is possible to be integrated into the microfluidic system and potentially be developed a portable diagnostic device.