Negatively charged bacteria adsorbed on positively charged graphene amine (a) Electrical response of graphene amine (GA) device upon attachment of a single bacterium on the surface of GA (inset 1). LIVE/DEAD confocal microscopy test on the bacteria deposited on GA confirmed that most of the bacteria were alive after the electrostatic deposition (inset 3). (a) Alive and (d) Dead. (b) DNA transistor: ssDNA tethering on GO increases the conductivity of the device. Successive hybridization and dehybridization of DNA on the G-DNA device results in completely reversible increase and restoration of conductivity. Inset shows a G-DNA(ds) sheet with wrinkles and folds clearly visible [154].