Interfacing Biomolecules, Cells and Tissues with Nanowire-based Electrical Devices - Applications of Electrochemistry and Nanotechnology in Biology and Medicine - page 72

cally modify them and to bind them specific receptors groups to
their surfaces.
The reproducible and tunable conducting properties of semi-
conducting nanowires, combined with the ability to bind desired
analytes on their surface yields electrical readout that offers revo-
lutionary conception, which has many advantages over conven-
tional organic molecular dyes for labeling and optical-based detec-
tion of biological and chemical entities. 19a
III. NANOWIRE FIELD EFFECT DEVICES FOR THE
DETECTION OF MOLECULAR SPECIES
The unique features of semiconductor nanowires have enabled to
produce highly sensitive devices that have been demonstrated for
variety of biological and chemical applications. In all reports, key
features such as direct, label free, real time, ultrahigh sensitivity,
exquisite selectivity and the potential for integration of addressable
arrays were shown, which set these devices apart from other sensor
technologies available today. In the following Section we discuss
representative examples which clearly demonstrate the potential of
these devices to significantly impact many areas of biology and
medicine.
NW-based FET can be configured as sensing device for bio-
logical and chemical molecules by linking receptor groups that
recognize specific molecules to the surface of the NWs, Fig. 1B
and C . SiNWs have native oxide coating that is naturally formed
with their exposure to air. Extensive data exist for the chemical
modification of silicon oxide or glass surfaces from planar chemi-
cal and biological sensors. 19b Practically, the receptor solutions are
delivered by a mated microfluidic channel to the chemically modi-
fied nanowires and the linkage is straightforward. When the sensor
device with surface receptor is exposed to a solution containing a
macromolecule like a protein or a chemical agent who has a net
charge in the aqueous solution, specific binding will lead to a
change in the surface charge that surrounds the nanowire and a
change in the conductance respectively.
As a proof of concept, a flexible integrated NW sensor plat-
form was developed, that incorporates SiNWs with well defined p-
or n-type doping; source and drain electrodes that are insulated