| Detection
of Pathogenic Viruses |
-----RMD has developed a proprietary
technology for rapid, sensitive detection of pathogenic
viruses that utilizes capture on paramagnetic nanoparticles,
combined with a novel measurement of the time dependence
of the magneto-optical birefringence exhibited by the complex.
Initially, the pathogenic virus is captured on the surface
of antibody-coated magnetic nanoparticles in a microfluidic
mixing device. These magnetic nanoparticle-virus complexes
exhibit a birefringence relaxation behavior in liquid suspension
that differs greatly from that of free, uncomplexed nanoparticles.
Relaxation of the magnetically induced birefringence results
in a characteristic time that is proportional to the hydrodynamic
volume of the magnetic nanoparticle-virus complex. As few
as several hundred virus particles can be detected by this
technique.
-----There is a need for
a sensitive, robust biosensor to detect the presence in
air of pathogenic bacteria released during a bioterrorist
attack. To satisfy this need, RMD is developing a biosensor
to be installed in train stations and other high traffic
venues that will periodically sample the air, rapidly test
for the presence of pathogenic bacteria, and alert the proper
authorities if such bacteria are detected. The device will
consist of four stages: an aerosol collector to concentrate
particles from the air into a liquid, fluorescent labeling
and capture with antibody-coated magnetic beads, washing
and release of the captured bacteria, and the detection
and identification of the bacteria with specific affinity
cartridges and avalanche photodiodes. Technologies employed
include: aerosol collection, microfluidics, antibody-coated
magnetic bead capture, and biophotonics.
-----The manipulation of liquids
in channels with dimensions of several tens of micrometers
is a major theme in our experimental technologies. Microfluidics
provide a great advantage over conventional fluid handling
techniques because they consume small amounts of sample
and reagents, and they optimize rates of solution phase
reactions by virtue of the confinement of diffusional freedom
of the fluids being manipulated. A microfluidic platform
is also capable of localizing particulate suspensions and
soluble molecular species within the detection range of
microoptical and microelectronic sensors - thus enabling
both high resolution and high-sensitivity detection. While
microfluidic technologies do pose additional problems associated
with achieving good mixing of colloidal samples due to the
laminarity of fluid flow, these difficulties can be overcome
by limiting diffusional pathways and introducing means of
achieving chaotic advection. Furthermore, the development
of multi-stream processing and the temporal control over
the introduction of reagents into the processing streams
conveyed by laminarity, will lead to automated management
of different chemistries without the usual costly investment
in processing equipment.
| All solid
state flow cytometer |
-----The Bisosensor
Technology group is developing a flow cytometer based on
Avalanche Photodiodes (APDs). These solid state silicon
based detectors with high internal gain can be used to replace
the photomultiplier tubes in conventional flow cytometers.
The APD detector elements have a peak quantum efficiency
of 80% near 900 nm, and have at least 40% quantum efficiency
over the 400 nm to 1000 nm wavelength range. The APD detectors
can be quite small (1 mm²) and are therefore useful
for a compact system. APDs also enable a broader wavelength
detection range (1100 nm), allowing for more fluorescent
labels on cell samples. The increase in the number of fluorescent
labels increases the information content on the cell and
improves the epitope identification.
-----The Biosensor team is
also developing a 16 element detector array for the flow
cytometer. The array is configured with dispersive grating
to simultaneously record emissions over a broad wavelength
range using the 16 APD channels of the linear APD array.
Information from the 16 discrete wavelengths provide more
data for better compensation and spectral decomposition
to resolve well cell populations.
| Complete
Blood Count Analysis |
-----We are exploring the
development of a microfluidic scale combination of cell
counter/flow cytometer for complete blood count analysis
(CBC). Our chip design utilizes a compact modular platform
of microfluidics that processes blood samples, performs
electronic and photonic measurements that fully characterize
red cells and platelets, and produces a five-way differential
analysis of leukocytes. This Micro Electro-Mechanical System
(MEMS) based platform will be capable of providing a CBC
analysis from a few microliters of peripheral blood. The
portability, small sample requirements, and modest cost
of the CBC chip will enable many point-of-care applications
to become feasible and drive down the cost of medical testing.
-----In addition, the Biosensor
Technology group is developing an automatous microfluidic
platform that is capable of detecting and analyzing biological
and disease markers from very small amounts of body fluids.
Our strategy involves selective capture of the biomarker
followed by electrochemical detection.
-----Finally, the
team is aimed at developing molecular barcodes for tagging
multiplexed biological assays. Our barcode will be composed
of combinations of fluorophores as distinguished by the
wavelength and lifetime of emission. The fluorophores will
be impregnated in micron-sized beads, the surface of which
can be modified with any type of biological probe, including
oligonucleotides and antibodies.
Next: Group
Leader
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