Carbon nanotubes field effect transistors biosensors

Carbon nanotube transistor arrays (CNTFETs) were used as biosensors to detect DNA hybridization and to recognize two anabolic steroids, stanozolol (Stz) and methylboldenone (MB). Single strand DNA and antibodies specific for STz and MB were immobilized on the carbon nanotubes (CNTs) in situ in the device using two different approaches: direct noncovalent bonding of antibodies to the devices and covalently trough a polymer previously attached to the CNTFETs. A new approach to ensure specific adsorption of the biomolecules to the nanotubes was developed. The polymer poly (methylmethacrylate(0.8)-co-poly (ethyleneglycol) methacrylate(0.8)-co-N-succinimidyl methacrylate(0.1)) was synthesized and bonded noncovalently to the nanotube. Aminated single-strand DNA or antibodies specific for Stz and MB were then attached covalently to the polymer. Statistically significant changes were observed in key transistor parameters for both DNA hybridization and steroids recognition. Regarding the detection mechanism, in addition to charge transfer, Schottky barrier, SB, modification, and scattering potential reported by other authors, an electron/hole trapping mechanism leading to hysteresis modification has been determined. The presence of polymer seems to hinder the modulation of the electrode-CNT contact.