Nanosensors are used in the detection of pathogens, contaminants, nutrients, environmental characteristics such as light/dark, hot/cold, wet/dry, heavy metals, particulates and allergens. Detection of very small amounts of a chemical contaminant, virus, or bacteria in agricultural and food systems is also possible. This is done by the integration of chemical, physical and biological devices working together as an integrated sensor at the nanoscale. Successful development of biosensor system involves sample preparation either by purification and concentration, target capture by recognition of biomolecules with high affinity and specificity for target. For example capturing via adsorption on glass, plastic, magnetic beads or through affinity binding, generation of signal that can be read by the detection system. One such example can be with reflection, florescence, bioluminescence, absorption of light, density and other techniques or by electrical signal. Signal and amplification, signal detection, data processing/interpretation/application and optimization is necessary for each step independently. The bioanalytical nanosensors either use biology as a part of the sensor, or are used for biological samples. Applications of nanosensors include the field of food Production, storage, manufacture and distribution, in the fast and accurate detection and exact diagnosis and treatment of diseses and in the field of bio terrorism.