Electrochemical impedance immunosensor based on gold nanoparticles-protein G for the detection of cancer marker epidermal growth factor receptor in human plasma and brain tissue.

A sensitive label-free impedimetric immunosensor for the detection of cancer biomarker epidermal growth factor receptor (EGFR) was developed with a limit of detection as low as 0.34 pg mL(-1) in PBS and 0.88 pg mL(-1) in human plasma. The gold nanoparticles were electrodeposited to modify the gold surface and to increase the electrochemical active area by a factor of approximately 3, i.e. by 68%. Protein G was used as scaffold for well oriented EGFR antibodies immobilization. Under optimal experimental parameters, the impedance changes were used for the detection of EGFR with a wide dynamic range of 1 pg mL(-1)-1 μg mL(-1). The immunosensor showed an excellent reproducibility and selectivity against biomarkers, murine double minute 2 and platelet derived growth factor receptor. The excellent analytical performance of the EGFR immunosensor in terms of selectivity, sensitivity and low detection limit might be attributed to the synergetic effect between the Au nanoparticles and the protein G scaffold. The matrix effect from mouse brain tissue homogenate was also studied and the immunosensor showed excellent recoveries ranging from 98.3% to 115% and RSD of 1.55-6.17. Finally, our developed strategy could open new avenues for clinical screening and prognosis of tumors.