Electrode asymmetry driven self-gating effect on the electrical detection of protein

Aptamer-immobilized gold nanoparticles (AuNP)/single-walled carbon nanotube (SWNT) field effect transistor (FET) sensors are fabricated for the detection of the ErbB2 protein. The 5′-thiol-modified 40-mer naphthyl DNA aptamers are immobilized on the AuNPs using well-established thiol chemistry. Carbodiimidazole-activated tween 20 (CDI-tween 20) layers are also introduced to the surface of the SWNT via hydrophobic interactions for blocking the attachment of nonspecific substances. Quantitative experiments reveal the specific binding effect of ErbB2 on the electrical measurements by comparing the electrical responses from a non-specific binding and control aptamer experiments. Under the optimized experimental conditions, the ErbB2 protein is clearly detectable at concentrations as low as 10 pM. The self-gating effect of the present device with a concentric electrode is able to provide a reliable electrical measurement scheme by circumventing the limits related to the isoelectric point of the target protein. Furthermore, the sensor fabrication, treatment and detection method have the potential to meet the following requirements: simplicity, portability, low cost and no need for bulky optical instruments.