We report direct, real-time electrical detection of single virus
particles with high selectivity by using nanowire field effect
transistors. Measurements made with nanowire arrays modified
with antibodies for influenza A showed discrete conductance
changes characteristic of binding and unbinding in the presence of
influenza A but not paramyxovirus or adenovirus. Simultaneous
electrical and optical measurements using fluorescently labeled
influenza A were used to demonstrate conclusively that the conductance
changes correspond to bindingunbinding of single viruses
at the surface of nanowire devices. pH-dependent studies
further show that the detection mechanism is caused by a field
effect, and that the nanowire devices can be used to determine
rapidly isoelectric points and variations in receptor-virus binding
kinetics for different conditions. Lastly, studies of nanowire devices
modified with antibodies specific for either influenza or
adenovirus show that multiple viruses can be selectively detected
in parallel. The possibility of large-scale integration of these
nanowire devices suggests potential for simultaneous detection of
a large number of distinct viral threats at the single virus level.