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Carbon Nanotube Sensors

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Title: Carbon Nanotube Sensors


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Carbon Nanotube Sensors
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Optical Nanosensors
9
What is a biosensor?
  • A biosensor is a device that consists of a
    biological recognition element or bioreceptor and
    a signal transducer.
  • When the analyte interacts with the bioreceptor,
    the resulting complex produces a change which is
    converted into a measurable effect (e.g. an
    electrical signal) by the transducer.

Antigen is tagged with fluorescent dye or
nanoparticles
Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
10
Common types of bioreceptors/analyte complexes
  • Antibody/antigen interactions
  • Nucleic acid interactions
  • Enzymatic interactions,
  • Cellular interactions (e.g. microorganisms,
    proteins) and
  • Interactions using biomimetic materials (e.g.
    synthetic bioreceptor)

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
11
Some of the signal transduction methods
  • Optical measurements (e.g. luminescence,
    absorption, surface plasmon resonance, etc.)
  • 2) Electrochemical (e.g. potentiometric,
    amperometric, etc.) and
  • 3) Mass-sensitive measurements (e.g. surface
    acoustic wave, microcantilever, microbalance,
    etc.)

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
12
Applications of Nanobiosensors
  • Nanosensors in biological systems
  • Size Requirements
  • (1) Nanostructures can be so small that the body
    may clear them too rapidly for them to be
    effective in detection or imaging. Larger
    nanoparticles may accumulate in vital organs,
    creating a toxicity problem. Scientists will need
    to consider these factors as they attempt to
    create nanodevices the body will accept.

http//press2.nci.nih.gov/sciencebehind/nanotech/n
ano04.htm
13
Nanosensors in Biological Systems Requirements
Cont.
  • Size Requirements
  • (2) Nanodevices should be small enough to enter
    cells.
  • Most animal cells are 10,000 to 20,000
    nanometers in diameter. This means that nanoscale
    devices (less than 100 nanometers) can enter
    cells inside them to interact with DNA and
    proteins. Tools developed through nanotechnology
    may be able to detect disease in a very small
    amount of cells or tissue. They may also be able
    to enter and monitor cells within a living body.

http//press2.nci.nih.gov/sciencebehind/nanotech/n
ano06.htm
14
Nanobiosensors in Cancer Detection
  • Detection of cancer at early stages is a critical
    step in improving cancer treatment. Currently,
    detection and diagnosis of cancer usually depend
    on changes in cells and tissues that are detected
    by a doctor's physical touch or imaging
    expertise. Instead, scientists would like to make
    it possible to detect the earliest molecular
    changes, long before a physical exam or imaging
    technology is effective.

http//press2.nci.nih.gov/sciencebehind/nanotech/n
ano07.htm
15
Improvement
  • Traditional cellular analysis approaches involve
  • fixingof the sample before analysis. This
    procedure
  • often destroys cellular viability and may
    significantly
  • alter intracellular architecture as compared to
    the
  • living state. However, the nanobiosensors can
    provide
  • unique tools to investigate important
    biological processes
  • at the cellular level in vivo.

http//www.ornl.gov/engineering_science_technology
/sms/Hardy20Fact20Sheets/Nanosensor20for20InVi
vo.pdf
16
Schematic diagram depicting the steps involved
with nanosensor fabrication.
Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
17
Pulling of optical fibers
  • These nanoprobes are fabricated by pulling a
    large silica optical fiber using a micropipette
    puller that is optimized for optical fibers
    yielding fibers with submicron diameters.
  • These typically have diameters ranging from 20 to
    80 nm depending on the pulling parameters used.

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
18
Silver coating of fiber
  • Following pulling of the fiber, approximately 200
    nm of silver, aluminum, or gold is deposited on
    the side of the tapered fiber using a vacuum
    evaporator.
  • This coating help us to prevent light leakage.
  • The fiber axis forms an angle of approximately
    450 with respect to the evaporation direction,
    while the fibers are rotated.
  • By angling the fiber in the evaporator, the
    nanometer end of the fiber remains free of metal.
  • The final tip diameter typically ranges from 200
    to 300 nm.

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
19
Continued
SEM image of a metal-coated nanofiber
Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
20
Antibody binding
  • The film must be uniform, adherent, thin,
    chemically and physically stable when in contact
    with its working medium and it must not
    electrically short-circuit
  • The antibody must have high specificity and low
    non specific binding

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
21
Formation of monolayers
  • Monolayers and isolated molecular layers can be
    formed using many techniques, some of them are
  • scanning probe microscopes (SPM)
  • self-assembled molecules (SAM) and
  • Langmuir-Blodgett films

22
Setup for Langmuir - Blodgett Deposition
Source http//www.public.iastate.edu/miller/nmg/
lbfilms.html
23
Transferring Monolayers
Source http//www.public.iastate.edu/miller/nmg/
lbfilms.html
24
A KSV 2200LB Langmuir-Blodgett System
25
Schematic diagram of the optical measurement
system used for intracellular measurements with
optical nanosensors.
Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
26
Optical measurement system
  • For the measurements of Benzo pyrene tetrol (BPT)
    the 325 nm line of a He-Cd laser was focused onto
    a 600 mm delivery fiber that terminated with an
    SMA connector.
  • The antibody-based nanosensor was then coupled to
    the delivery Fiber through an SMA connector and
    was secured to micromanipulators on an inverted
    microscope

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
27
Continued ..
  • Fluorescence emission from the analyte was
    collected by the microscope objective, passed
    through a 400 nm long pass dichroic mirror to
    remove any scattered laser light, and then
    focused onto a photo multiplier tube (PMT) for
    detection.
  • The PMT output was then passed to a picoammeter
    and recorded using a personal computer
  • Images were obtained using a charge-coupled
    device (CCD) mounted to the side port of the
    microscope.

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
28
Single-cell measurements using antibody based
nanosensors
  • Fiber optic nano-biosensors have even been used
    to perform measurements in various locations
    within mammalian cells, which are approximately
    10 um in diameter.
  • Antibody-based fiber optic nano-biosensors for
    BPT were used to obtain quantitative measures of
    BPT within the cytoplasm of two cell lines (1)
    human mammary carcinoma cells and (2) rat liver
    epithelia cells following BPT exposure.

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
29
Continued..
  • These measurements demonstrated that the
    concentration of BPT inside the cytoplasm of both
    cell lines was the same, suggesting a similar
    means of transport through the cell membrane.
  • Therefore, by using nanosensors specific to
    various compounds,it should be possible to
    determine transport mechanisms through various
    intracellular membranes.

Nanosensors and biochips frontiers in
bimolecular diagnostics, Sensors and Actuators B
Chemical, Volume 74, Issues 1-3, 15 April 2001,
Pages 2-11
30
Nanobiosensors in Cancer Detection ,Cont.
  • Nanosensor Probes Single Living Cells

A nanosensor probe carrying a laser beam(blue)
penetrates a living cell to detect the presence
of a product indicating that a cell has been
exposed to a cancer- causing substance.
http//www.ornl.gov/ORNLReview/rev32_3/nanosens.ht
m
31
Nanobiosensors in Cancer Detection, Cont.
  • How does it happen?
  • When the cells are exposed to ben-zoapyrene
    (BaP), a known cancer-causing environmental agent
    often found in polluted urban atmospheres, it
    reacts with the cell's DNA, forming a DNA adduct,
    which can be hydrolyzed into a product called
    benzo(a)pyrene tetrol (BPT).
  • Then the damage of DNA occurred, so BPT in
    the cell is a sign of early cancer.

http//www.ornl.gov/ORNLReview/rev32_3/nanosens.ht
m
32
Nanosensors in Cancer Detection Cont.
  • How does it happen? cont.
  • The nano-needle is really a 50-nm-diameter
    silver-coated optical fiber that carries a
    helium-cadmium laser beam. Attached to the
    optical fiber tip are monoclonal antibodies that
    recognize and bind to BPT.

http//www.ornl.gov/ORNLReview/rev32_3/nanosens.ht
m
33
Nanobiosensors in Cancer Detection, Cont.
How does it happen? cont. The laser light, which
has a wavelength of 325 nm, excites the
antibody-BPT complex at the fiber tip, causing
the complex to fluoresce. The newly
generated light travels up the fiber into an
optical detector. The layer of silver is
deposited on the fiber wall to prevent the laser
excitation light and the fluorescence emitted by
the antibody-BPT complex from escaping through
the fiber.
http//www.ornl.gov/ORNLReview/rev32_3/nanosens.h
tm
34
Nanobiosensors in Cancer Detection, Cont.
  • How does it quantitatively estimate the
    concentration of BPT?
  • Calibration procedures
  • Need a series of measurements, by plotting
    the increase in fluorescence from one
    concentration to the next versus the
    concentration of BPT,and fitting these data with
    an exponential function.

Brian M. Cullum and Tuan Vo-Dinh, trends of
biotechnology,18(9)388-393,2002
35
Future Nanobiosensors
  • Researchers aim eventually to create nanodevices
    that do much more than deliver treatment. The
    goal is to create a single nanodevice that will
    do many things assist in imaging inside the
    body, recognize precancerous or cancerous cells,
    release a drug that targets only those cells, and
    report back on the effectiveness of the treatment

http//press2.nci.nih.gov/sciencebehind/nanotech/n
ano20.htm
36
Future Nanosensors,cont
  • Improving activity of gene therapy
  • Oral vaccinations
  • Magnetite - dextran nanoparticles for MRI
    diagnosis of liver, lymph node, vascular
    diseases

http//www.rpi.edu/locker/25/001225/public_html/na
nowebprojects/laurasmith/nanosensors.ppt
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