New “ON-OFF”-type nanobiodetector

Abstract A new type of nanobiodetector based on a limited number of polyaniline nanofibrils has been designed and tested against bacteria Klebsiella pneumoniae , Pseudomonas aeruginosa , Escherichia coli and Enterococcus faecalis . The cells attaching conducting nanofibrils modify locally the electrical conductivity making the polymer nanowires electrically inhomogeneous. The “defects” accumulate in nanofibrils changing suddenly their electrical conductivity above a threshold density (the percolation limit), enabling an easy flow of the charge carriers. The results are unique: the device works like an “ON-OFF” switch with nearly linear response above a threshold number of cells in the suspension examined, which is of an order of 10 5 to 10 6 CFU per 1 ml. Such a behaviour is important for bio-alarm systems, environmental monitoring and medical applications.