**5. Conclusion**

Toxins are polypeptide diffusible proteins that are released by bacterial species that cause diseases due to drastic interactions of pathogen and host cell. Toxins may enter the cell membrane surfaces by damaging it and facilitate the interaction with other cells. Toxins are diverse in their size, mode of secretion, mechanism of action, structure, enzymatic activity, membrane/intracellular receptor recognition and spore forming activity. Various protein molecules are being released by bacteria that cause invasion of the host. Exotoxins differ in biological function, molecular structure, immunological properties and mechanism of secretion. Structure of bacterial toxins is based on rather unconventional strategies. The diversity in toxins is mainly due to structural organization and functions. These elemental variations play an important role in their flexibility and dynamics. Biological toxins are being used extensively in bioterrorism. Various biological toxins involved in the inhibition or disruption of nerve impulse transmission ultimately causing cellular death. These toxins having potential to use as biological weapons for terrorism or military use. These toxins are considered most suitable for bioterrorist attacks due to cost effective and ease of production along with the high toxicity and environmental stability. Various techniques have been used to identify the pathogens and toxins but these diagnostic methods are some limitation such as time consuming, laborious and bulky instrumentation etc. Among all, engineered naonoparticles is advanced, cost effective and sensitive technique for screening of toxins. The nanoparticles like polymerica and quantam dots, nanochips, carbon nanotubes, cantilevers etc. effectively used for the diagnosis of toxins. The flouresence molecules are also tagged in nanoparticles which help in detection process. Researchers are working on the designing of smart 2 or 3D nanohips that helps in diagnosis of toxin with minimum sample volume in less time. Microorganisms especially bacterial strains develops a resistance mechanisms against drugs, so the advancement in nanotechnology not only able to detect the toxins but also assess whether the bacterial strains are resistant to drugs.
