Insect chemoreceptors coupled to silicon transistors as innovative biosensors

Applications like the warning about agricultural pest infestations, the detection of spoilt food during storage and transport as well as the monitoring of smoldering fires require highly selective odor sensing techniques. Insect antennae that have been optimized by evolution over million of years are most suitable for such a sensitive and selective detection of certain organic substances in air. The utilization of this highly specialized sense of smell from insects needs in terms of analytical tools, however, an adaptation of the antenna to the microelectronic technique. Therefore, a beetle/FET (field-effect transistor) interface as an innovative biosensor has been developed. This BioFET (biologically sensitive FET) is based on the direct combination of the intact chemoreceptor of an insect with the gate of a FET by means of an electrolyte solution. Depending on the experimental set-up, two different biosensor configurations, namely a whole-beetle BioFET and an isolated-antenna BioFET have been designed. In both configurations, the organic compound that is detected by the beetle initiates a recognition process at its nerve cell membranes, which results in a net potential over the whole insect antenna. Then, this potential drop modified the gate conductivity and consequently, the drain current of the FET. By applying various kinds of insect antennae (e.g. of the Colorado potato beetle and the steelblue jewel beetle) different odor concentrations, such as cis3-hexen-1-ol, guaiacol and 1-octen can be detected down to the low ppb range.