A device for determining the presence of a single cell and/or determining a state of a single cell includes a first nanotube disposed on a first electrode, and a second nanotube disposed on a second electrode, wherein the first and second nanotubes are spaced apart at a length that is smaller than a cell size to be detected. A method for determining the presence of a single biological cell includes sensing impedance between a first nanotube and a second nanotube. A method of manufacturing includes providing a nanotube, providing an electrode coated with an insulating material, wherein an aperture is defined in the insulating material through to the electrode, and using electrophoresis deposition to deposit a nanotube within the aperture and in electrical communication with the electrode.