U.S. patent application number 10/940256 was filed with the patent office on 2005-02-17 for fiber-optic flow cell and method relating thereto.
This patent application is currently assigned to Luna Innovations, Inc.. Invention is credited to Averett, Joshua P., Elster, Jennifer L., Jones, Mark E., Pennington, Charles D..
Application Number | 20050036140 10/940256 |
Document ID | / |
Family ID | 32312515 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050036140 |
Kind Code |
A1 |
Elster, Jennifer L. ; et
al. |
February 17, 2005 |
Fiber-optic flow cell and method relating thereto
Abstract
The present invention is for a fiber optic flow cell. The flow
cell comprises a substrate having at least one sample channel and
at least one optical fiber channel holder. At least one optical
fiber is disposed within each optical fiber channel holder. Each
optical fiber has at least one grating wherein each grating is in
contact with each sample channel, defining a sensing area. At least
one sample port is positioned in an operable relationship to at
least one sample channel. Alternatively, at least one sample outlet
is positioned in an operable relationship to at least one sample
channel. The flow cell may be of a modular design providing a flow
cell kit that contains pieces that may be assembled to form
custom-made flow cells. The flow cell is used for conducting
measurement studies on a sample.
Inventors: |
Elster, Jennifer L.;
(Blacksburg, VA) ; Jones, Mark E.; (Blacksburg,
VA) ; Pennington, Charles D.; (Blacksburg, VA)
; Averett, Joshua P.; (Radford, VA) |
Correspondence
Address: |
JOY L BRYANT
P O BOX 590
LIGHTFOOT
VA
23090
|
Assignee: |
Luna Innovations, Inc.
Blacksburg
VA
|
Family ID: |
32312515 |
Appl. No.: |
10/940256 |
Filed: |
September 14, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10940256 |
Sep 14, 2004 |
|
|
|
10695236 |
Oct 28, 2003 |
|
|
|
60422495 |
Oct 31, 2002 |
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Current U.S.
Class: |
356/246 ;
356/133 |
Current CPC
Class: |
G01N 2015/0693 20130101;
G01N 21/05 20130101 |
Class at
Publication: |
356/246 ;
356/133 |
International
Class: |
G01N 021/05; G01N
021/41 |
Claims
What is claimed is:
1. A process for conducting measurement studies on a sample and a
flow cell, the process comprising the steps of: a) providing a flow
cell comprising a substrate having at least one sample channel and
at least on optical fiber channel holder; at least one optical
fiber disposed within each optical fiber channel holder, wherein
each optical fiber has at least one grating wherein each grating is
in contact with each sample channel, defining a sensing area; and
at least one sample port positioned in an operable relationship to
at least one sample channel; b) introducing at least one sample
into the flow cell through at least one sample inlet; c) allowing
each sample to flow into each sample channel; d) measuring
characteristics of the sample and the flow cell at the sensing
area; and e) removing the sample from each sample channel.
2. A process according to claim 1, wherein the flow cell further
comprises at least one sample outlet positioned in an operable
relationship to at least one sample channel.
3. A process according to claim 1, further comprising the step of
introducing at least two different samples into the flow cell
through at least one sample port and allowing the samples to mix in
one sample channel.
4. A process according to claim 1, wherein the physical
characteristics of the sample are selected from the group
consisting of: temperature; pressure; refractive index; and pH.
5. A process according to claim 2, wherein the physical
characteristics of the sample are selected from the group
consisting of: temperature; pressure; refractive index; and pH.
6. A process according to claim 1, wherein the sample is selected
from the group consisting of: a liquid sample; a gas sample; and a
complex sample.
7. A process according to claim 2, wherein the sample is selected
from the group consisting of: a liquid sample; a gas sample; and a
complex sample.
8. A process according to claim 1, wherein the characteristics of
the sample are biochemical characteristics.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of application Ser. No.
10/695,236 filed Oct. 28, 2003, entitled, "Fiber-Optic Flow Cell
and Method Relating Thereto," which claims the benefit of U.S.
Provisional Patent Application No. 60/422,495, entitled "Device for
Liquid and Air Sampling and Detection Using Optical Fiber-Based
Sensors," filed Oct. 31, 2002, both applications are incorporated
by reference herein in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to flow cells. In particular,
it relates to a flow cell having a grating-based optical fiber
sensor incorporated therein.
BACKGROUND OF THE INVENTION
[0003] Flow cells have been constructed for liquid-phase
measurements using fluorescent-based devices that require the
sensor surface to be in contact with the environment. These flow
cells are primarily designed to enhance the sensing characteristics
of a particular component by blocking background light from
influencing the sensor response. The device enclosure is
constructed in a way to limit background light, a primary noise
factor in fluorescent applications. Because the primary purpose of
the cell is to control coupled light, the cell does not take into
account rigid support for the optical fiber or additional
processing needs such as mode stripping. In addition, flow cells
have configurations that require external pumps or other methods to
bring the external environment to the sensor as opposed to directly
exposing the sensor to the external environment.
[0004] Crotts et al. (U.S. Pat. No. 6,215,943 B1) describe an
optical fiber holder that allows a sample to be tested while
avoiding strain and bending influences. The holder comprises a tube
having a longitudinal axis, a first end for receiving an optical
fiber and a recessed second end for protecting the optical fiber
tip. An aperture is disposed along a length of the longitudinal
axis of the tube for exposing the optical fiber to a sample. A
change in a sample is determined by disposing an optical fiber
device having a sensing element into the optical fiber holder. The
optical fiber holder is then inserted into a vessel containing a
sample and the sample is circulated past the sensing element. The
problem with this device is that it requires that a large enough
sample volume be available to submerge the device and to circulate
the sample past the sensor. Therefore, small (microliter) samples
cannot be used. In addition, there is no way to control the manner
by which the sample contacts the sensor. This is of particular
importance when one desires to conduct kinetic studies. Kinetic
studies and studies where it is desirable to obtain results in
real-time as various samples come into contact with one another are
difficult to conduct with this device because the method of dipping
is limited by diffusion. Moreover, this configuration is only
applicable to large sample sizes. When sample sizes are on the
microliter scale, the holder is reduced dimensionally and loses its
structural rigidity and, hence, its capability to measure
adequately.
[0005] Malmqvist et al. (U.S. Pat. No. 6,200,814 B1) provides a
method and device for controlling a fluid flow over a sensing
surface within a flow cell. The methods employ laminar flow
techniques to position a fluid flow over one or more discrete
sensing areas on the sensing surface of the flow cell. Such methods
permit selective sensitization of the discrete sensing areas, and
provide selective contact of the discrete sensing areas with a
sample fluid flow. The method requires that the surface of the
sensor be sensitized by activating the sensing surface such that it
is capable of specifically interacting with a desired analyte. The
sensor device comprises a flow cell having an inlet end and an
outlet end; at least one sensing surface on a wall surface within
the flow cell located between the inlet and outlet ends; wherein
the flow cell has at least two inlet openings at the inlet end, and
at least one outlet opening at the outlet end, such that separate
laminar fluid flows entering the flow cell through the respective
inlet openings can flow side by side through the flow cell and
contact the sensing surface. In this aspect, the flow cell and the
sensing surface are one in the same. In another aspect of the
invention, the sensor system comprises a flow cell having an inlet
end and an outlet end; at least one sensing area on a sensing
surface within the flow cell between the inlet and outlet ends; the
flow cell having at least two inlet openings at the inlet end, and
at least one outlet opening at the outlet end; means for applying
laminar fluid flows through the inlet opening such that the laminar
fluid flows pass side by side through the flow cell over the
sensing surface; means for varying the relative flow rates of the
laminar flows of fluids to vary the respective lateral extensions
of the laminar flows over the sensing surface containing the
sensing area or areas; and, detection means for detecting
interaction events at the sensing area or areas. These flow cells
are designed such that the sensing surface is a part of the wall
surface within the flow cell. When the sensor is part of the flow
cell wall, there is no way to route an optical fiber. Thus, the
flow cell design does not allow incorporation of an optical fiber
sensor.
[0006] Jorgenson et al. (U.S. Pat. Nos. 5,359,681; 5,647,030; and
5,835,645) disclose a fiber optic sensor which detects a sample in
contact with the sensor by surface plasmon resonance (SPR)
measurements. The sensor includes a surface plasmon supporting
metal layer in contact with an exposed portion of the optical fiber
core. Detection of a sample with the fiber optic SPR sensor is
made, in part, by contacting the sample with the sensing area of
the optical fiber. The sensing area is made by exposing a portion
of the optical fiber core by removal of the surrounding cladding or
cladding/buffer layers, and adhering an SPR supporting metal layer
to the exposed optical fiber core. The SPR supporting metal layer
of the optical fiber is then exposed to the sample of interest, and
the refractive index of the sample is determined. The problem with
this configuration is that it is difficult to keep the optical
fiber straight while mass producing the flow cell with consistency.
Moreover, the invention does not address a method for optimizing
sampling.
[0007] An object of the present invention is to provide a flow cell
that allows for various studies to be conducted on a sample or a
variety of samples and sample combinations.
[0008] Another object of the invention is to provide a flow cell
that employs a grating-based optical fiber sensor system.
[0009] Another object of the invention is to provide a flow cell
that is capable of operation under varying flow rates with varying
sample sizes.
[0010] Another object is to present a flow cell that permits
measurement of reaction rates.
[0011] Another object of the invention is to provide a flow cell
that is easy to manufacture and assemble with consistency.
[0012] Another object of the invention is to provide a flow cell
that can be easily modified to achieve the desired testing
apparatus.
[0013] Another object of the invention is to provide a flow cell
design that provides the flexibility to increase the number of
sample channels without comprising the ability of the sensors
within the flow cell to make accurate measurements.
SUMMARY OF THE INVENTION
[0014] By the present invention, a flow cell is presented. The flow
cell comprises a substrate having at least one sample channel and
at least one optical fiber channel holder. At least one optical
fiber is disposed within each optical fiber channel holder. Each
optical fiber has at least one grating. Each optical fiber grating
is in contact with each sample channel, defining a sensing area. At
least one sample port is positioned in an operable relationship to
at least one sample channel.
[0015] In a further embodiment of the invention, the flow cell has
at least one sample outlet positioned in an operable relationship
to at least one sample channel. The flow cell may be of a
monolithic or piece-like structure. A flow cell kit contains at
least two mating pieces that may be reconfigured in a number of
arrangements depending on the desired application. The flow cell is
used for conducting measurement studies on a neat sample or a
complex mixture on a range of sample sizes, including samples of
less than 100 microliters.
[0016] An advantage to these arrangements is that the optical fiber
channel has sections in the flow cell where the optical fiber is
isolated from the sample channel. This permits easy manufacturing
of the flow cell without disturbing the configuration of the sample
channel.
[0017] Additional objects and advantages of the invention will be
set forth in part in the description which follows, and in part
will be obvious from the description, or may be learned by practice
of the invention. The objects and advantages of the invention will
be obtained by means of instrumentalities in combinations
particularly pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings illustrate a complete embodiment
of the invention according to the best modes so far devised for the
practical application of the principles thereof, and in which:
[0019] FIG. 1 is a cross sectional view of a flow cell embodiment
having two sample ports that act as either an inlet and/or an
outlet; a single sample channel; and a single optical fiber channel
holder.
[0020] FIG. 2A is a cross-sectional view of the flow cell having
two mating pieces.
[0021] FIG. 2B is a cross-sectional view of the flow cell assembly
when the two mating pieces are assembled together.
[0022] FIG. 3 is a cross-sectional view of the flow cell having
three mating pieces.
[0023] FIG. 4 is a cross-sectional view of the flow cell having a
single sample port and a plurality of sample channels.
[0024] FIG. 5 is a cross-sectional view of the flow cell having a
plurality of sample ports, a single sample channel, and a single
sample outlet.
[0025] FIG. 6 is a cross-sectional view of the flow cell having one
sample port, a plurality of sample channels, and one sample
outlet.
[0026] FIG. 7 is a cross-sectional view of the flow cell having one
sample port, a plurality of sample channels, and a plurality of
sample outlets.
[0027] FIG. 8 is a cross-sectional view of the flow cell having a
plurality of sample ports, one sample channel, and one sample
outlet.
[0028] FIG. 9 is a cross-sectional view of the flow cell having a
plurality of sample ports, one sample channel, and a plurality of
sample outlets.
[0029] FIG. 10 is a cross-sectional view of the flow cell having a
plurality of sample ports, a plurality of sample channels, and a
plurality of sample outlets.
[0030] FIG. 11A is a perspective view showing a flow cell array
formed by stacking several flow cells together.
[0031] FIG. 11B is a 3-dimensional view showing a stacked flow cell
array.
[0032] FIG. 12 is a schematic showing a flow cell array integrated
with other processes.
[0033] FIG. 13 is a graph depicting the reaction kinetic data when
the flow cell of the present invention is in use.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Referring now to the drawings, where similar parts are
numbered the same, FIG. 1 depicts a simple embodiment of the
invention where the flow cell 10 comprises a substrate 20 having at
least one sample channel 30 and at least one optical fiber channel
holder 35 disposed therein. For the purpose of this application and
the appended claims, an optical fiber channel holder is a holder
that is capable of achieving precision alignment and consistent
tension on the optical fiber. At least one optical fiber 40 is
disposed within each optical fiber channel holder 35. The optical
fiber 40 has at least one grating 50 disposed therein. The optical
fiber channel holder 35 is designed to come into contact with the
sample channel 30 at the points along the optical fiber where each
optical fiber grating 50 is located. These points define a sensing
area 55. At least one sample port 60 is positioned in an operable
relationship to at least one sample channel 30 to permit
introduction of a sample into the sample channel. Although two
sample ports are depicted, it is understood that there need only be
one sample port. When the flow cell has one sample port, the sample
is introduced into and exits from the flow cell through the same
port. The sample port 60 is positioned in an operable relationship
to the sample channel 30 such that the sample may easily flow into
the sample channel. In one embodiment of the invention, where the
flow cell comprises more than one sample port, at least one sample
port is plugged with a gas permeable material that allows air to
escape as a sample is introduced into another sample port.
Alternatively, a pump is attached to at least one sample port to
serve as a means for either drawing or pushing the sample through
the flow cell. Lastly, the sample port may serve as an exit port
for the sample after it flows through the flow cell. Multiple
sample ports may be employed when the user desires to introduce
multiple samples into the flow cell. Alternatively, a pipette tip
is formed on the sample port for drawing fluid samples into the
sample channel and through the substrate. This is especially
desirable when a microtiter plate arrangement is employed.
[0035] The sample channel is capable of being modified to achieve
the desired sample delivery volume to the sensing area (preferably
less than 100 microliters). The sample channel 30 is depicted in
its preferred configuration where the sample channel is curved to
provide optimal fluid flow within the sensor area. The curved shape
allows the flow to be laminar, thus eliminating dead volumes.
However, various geometries may be employed to enhance downstream
and upstream flow of the sample. Alternatively, the sample channel
30 may also be straight to easily prevent samples from being
trapped in the flow cell provided it is in contact with the grating
portion of the optical fiber.
[0036] The optical fiber 40 is positioned within an optical fiber
channel holder 35. Each optical fiber has a grating 50. The portion
of the optical fiber having the grating 50 is positioned within the
optical fiber channel holder 35 so that the grating 50 is in
contact with the sample channel 30, defining a sensing area 55.
This is the area where the sample contacts the optical fiber. The
amount of sample flowing into the sensing area is controlled by
modifying the dimensions of the sample channel by using different
geometries. The optical fiber has, at a minimum, one grating
disposed therein. The grating is either a Bragg grating or a long
period grating, depending on the sample under test. More than one
grating is disposed within the optical fiber when multiple test
points are desired. When multiple gratings are disposed within the
optical fiber, the optical fiber channel holder is configured such
that each grating contacts the sample channel. Moreover, the
optical fiber may be pre-treated with a reactive coating prior to
insertion into the optical fiber channel holder. Reactive coatings
are those coatings that are capable of undergoing a change when
exposed to a specific parameter such that it causes the long period
grating to produce a wavelength transmission spectrum functionally
dependent on the change which takes place. These types of coatings
are described in U.S. Pat. No. 5,864,641 to Murphy et al. which is
hereby incorporated by reference in its entirety. Alternatively,
the optical fiber may be treated in-situ by flowing a sample
containing a reactive species over the optical fiber grating prior
to introducing the sample into the flow cell. The optical fiber is
connected to an optical light source and a detector using
procedures known to those of skill in the art.
[0037] The design of the flow cell of the present invention
overcomes the problem of Crotts et al. where large sample sizes are
required. The novelty of the invention lies in the optical fiber
channel holder 35 which helps the optical fiber sustain a linear
shape and avoid possible distortion when it comes into contact with
a sample. This aids in preventing optical distortions that result
when the optical fiber is subject to sudden movements experienced
when various samples come into contact with the optical fiber. This
design is preferred over a design where the optical fiber is
disposed within the sample channel because the optical distortions
are reduced if not eliminated. Moreover, the optical fiber channel
holder enables the optical fiber to be routed through the flow cell
and facilitates alignment and simplifies fabrication procedures
such that the configuration of the sample channel is not
disturbed.
[0038] The substrate 20 gives rise to the overall shape of the flow
cell 10 and is either a monolithic structure or a piece-like
structure. In the case of a monolithic structure, the substrate is
pre-cast or a solid piece that has been bored-out to provide at
least one sample channel 30, at least one optical fiber channel
holder 35, and at least one sample port 60. The flow cell 10 is any
shape suitable for the desired application. In particular, the flow
cell is either a cylinder or a planar (meaning 2-dimensional)
structure.
[0039] FIGS. 2A and 2B depict a flow cell 10 comprised of two
mating pieces 70, 80. The upper portion 70 of the mating pieces
contains at least one sample channel 30 and at least one sample
port 60. FIG. 2A and 2B show a preferred embodiment where there is
a sample outlet 75 in fluid connection with the sample channel 30
such that the sample is removed from the flow cell through the
sample outlet 75. The lower portion 80 of the mating pieces
comprises at least one optical fiber channel holder 35 having an
optical fiber 40 with a grating 50 disposed therein, positioned
within the optical fiber channel holder 35. The optical fiber
channel holder 35 is, in this instance, drilled out of the base
such that it is essentially parallel to the sensing area. The
figures also depict an embodiment where an optical fiber connector
45 is disposed within the flow cell and forms an input/output
connection with the optical fiber. FIG. 2B shows a further
embodiment of the invention where an injection port 32 has been
incorporated with the sample port for introduction of a sample by
injection. Thus, the flow cell has both an optical and a fluid
connection within it. FIG. 2B depicts the structure of the flow
cell when the mating pieces have been assembled together. The
resulting structure may be of any geometric shape known to those of
skill in the art. Preferably, the mating pieces give rise to a
cylinder or planar structure. When the need arises, one may
incorporate various sealing means, such as gaskets, to prevent
leakage. FIG. 2B shows a sealing means 33 disposed at various
junctures in the flow cell to prevent fluid leakage. Such sealing
means may be of any means known to those of skill in the art such
as gaskets, adhesives, and various sealing compounds.
[0040] FIG. 3 depicts an alternative embodiment of the flow cell 10
comprised of three mating pieces. In this embodiment, there is an
upper section 100 containing at least one sample channel (not
shown) and at least one sample port 60. This portion is
counter-sunk to permit critical alignment of the optical fiber
channel holder 35 with the sample channel 30. In the middle section
110, there is the optical fiber channel holder 35 having the
optical fiber 40 disposed therein. The optical fiber channel holder
35 is configured to allow a space defining a sensing area 115 where
the grating portion of the optical fiber 40 is located. The optical
fiber channel holder is designed such that the sensing area and
flow cell walls are close to the fiber for diffusion purposes. The
lower section 120 of the flow cell serves as a support or base for
the assembly. As with the upper portion, the lower section 120 is
also counter-sunk to permit critical alignment of the optical fiber
channel holder 35 with the sample channel 30. The flow cell
assembly is joined and held together by a fastener. Any fastener
known to those of skill in the art may be used. Examples of such
fasteners include but are not limited to: screws; nuts and bolts;
male-female connectors that are fabricated as part of the
substrate; rivets; welds; adhesives; straps; crimp connectors such
as bent wire; bands fabricated from rubber, metal, plastic; and
clamps such as C-clamps. The use of multiple mating pieces allows
the user to modify the flow cell or reconfigure it. For example, an
upper section containing a single sample channel having one sample
port may be substituted with an upper section having multiple
sample channels having either one or multiple sample ports. If
desired, the upper section may also contain a sample outlet or
multiple sample outlets so the sample is removed from the flow cell
through an outlet other than the sample port. Alternatively, the
middle section may be exchanged to match the number of sample
channels of the upper section or may provide a single sensing area
where many samples converge. When the need arises, one may
incorporate various sealing means, such as gaskets, to prevent
leakage. Because of the versatility afforded by having a piece-like
structure, a flow cell kit is provided that allows the user to
design custom flow cells depending on the application. The kit
configuration makes the flow cell easy to clean. The ability to
disassemble the flow cell easily allows for the user to apply
various coatings to the cell that can be removed without causing
damage to the flow cell. A flow cell comprised of mating pieces
provides a significant advantage over the prior art flow cells
because it is easy to clean; can be easily converted for a
particular application; provides consistent manufacturing and test
results; and provides the flexibility to increase the number of
sample channels without compromising the measurements made in the
sensing area.
[0041] FIGS. 4 and 5 show alternative embodiments of the invention
where the number of sample ports and sample channels are varied and
the sample port serves as both an inlet and an outlet for the
sample. In these configurations, the sample channel 30 terminates
with a sample reservoir 37. This permits the sample to be contained
within the flow cell after it has passed through the sensing area
55. FIG. 4 depicts an embodiment where there is one sample port 60
and a plurality of sample channels 30. In this arrangement, the
sample enters and exits the flow cell 10 through the sample port
60. The optical fiber 40 is disposed within the optical fiber
channel holder 35. Sample measurements are made in the sensing area
55 where the optical fiber grating 50 is in close proximity to the
sample channel 30. FIG. 5 shows an alternative embodiment that
allows samples to be mixed within the flow cell 10. In this
embodiment, a plurality of sample ports 60 are provided but only
one sample channel 30, terminating with a sample reservoir, is
provided. The optical fiber 40 is disposed within the optical fiber
channel holder 35. A plurality of samples are introduced through
the sample ports 60, mixed in the sample channel 30, and detected
in the sensing area 55 of the flow cell where the grating 50 is in
close proximity to the sample channel. The mixed sample is removed
from the flow cell through the sample ports 60 upon completion of
the data collection process. Both figures depict a preferred
embodiment where an optical fiber connector 45 is attached to an
end of the optical fiber 40.
[0042] FIGS. 6-9 show further embodiments of the invention, where
the number of sample ports, sample channels, and sample outlets are
varied. FIG. 6 depicts an embodiment of the flow cell 10 having one
sample port 60, a plurality of sample channels 30, and one sample
outlet 75. In addition, the flow cell 10 has a fastening means 112
such that it may be interlocked with other flow cells. An optical
fiber channel holder 35 is positioned in an operable relationship
to each sample channel 30 such that, for each sample channel 30,
there is an optical fiber channel holder 35 positioned in an
operable relationship to it. Each optical fiber channel holder 35
has an optical fiber 40 disposed within it. Preferably, each
optical fiber 40 has an optical fiber connector 45 attached to an
end of the optical fiber 40. This configuration permits multiple
readings to be taken on a single sample. FIG. 7 depicts an
embodiment of the invention where there is one sample port 60, a
plurality of sample channels 30, a plurality of optical fiber
channel holders 35 each having an optical fiber 40 disposed
therein, and a plurality of sample outlets 75. Each optical fiber
40 has an optical fiber connector 45 affixed to an end of the
optical fiber 40. This arrangement allows multiple readings on a
single sample with quick removal through the sample outlets 75.
FIG. 8 shows an embodiment where the flow cell 10 has a plurality
of sample ports 60, one sample channel 30, one optical fiber
channel holder 35 having one optical fiber 40 disposed therein and
terminating at one end with an optical fiber connector 45, and one
sample outlet 75. This configuration allows for sample mixing in
the sample channel 30 by allowing different samples to be
introduced into the flow cell. Also depicted is a fastening means
112 for assembling the flow cell 10 with other flow cells. The flow
cell 10 of FIG. 9 has a plurality of sample ports 60, one sample
channel 30, one optical fiber channel holder 35 having one optical
fiber 40 disposed therein and terminating at one end with an
optical fiber connector 45, and a plurality of sample outlets 75.
This configuration allows for mixing of samples in the sample
channel 30 plus quick removal of the sample through the sample
outlets 75. In addition, fasteners 112 are provided for assembling
the flow cell 10 with other flow cells.
[0043] FIG. 10 depicts another embodiment of the invention where
the flow cell 10 comprises a plurality of sample ports 60; a
plurality of sample channels 30; a plurality of optical fiber
channel holders 35 having one optical fiber 40 disposed therein and
terminating at one end with an optical fiber connector 45, and a
plurality of sample outlets 75. This configuration provides the
user with the ability to inject many different samples into the
flow cell 10 through the sample ports 60 and removal of the samples
through the sample outlets 75. In addition, fasteners 112 are
provided for assembling the flow cell 10 with other flow cells.
[0044] FIGS. 11A and 11B depict how a flow cell array 125 is
assembled by stacking various flow cell assemblies 10 together.
Each flow cell 10 has a means for interlocking with another flow
cell (not shown). In a most preferred embodiment of the invention,
the flow cell has at least one sample outlet 75, at least one
sample channel 30, and 2, 8, 96 384, or 1536 sample ports. In
addition, each flow cell has at least one sample port 60. Also
depicted is a preferred embodiment where each optical fiber (not
shown) terminates with an optical fiber connector 45. When there
are multiple sample channels, each channel is spaced apart a
distance of less than or about 9 mm. This spacing makes the flow
cell compatible with micro titer plates which are the sample plates
used in life sciences research. The tip volumes and spacing between
the tips are designed into the flow cell for microtiter interface.
In addition, when the flow cell comprises mating pieces, quadrant
sampling can be used to interface with high capacity plates such as
384 and 1536 micro titer plates (FIGS. 11A and 11B).
[0045] As a further embodiment to the invention, each sample port
has a means to control delivery of the sample into each sample
channel. Such means may be any known to those of skill in the art.
In particular, the means may be by aspiration, continuous flow, and
continuous flow with dwell time when there is no sample outlet. If
a sample outlet is part of the flow cell, then the means may also
include a continuous loop. When a sample is introduced by
aspiration, it undergoes a back and forth motion within the sample
channel. Continuous flow involves the movement of the sample into
the portion of the sample channel containing the optical fiber in
such a way that there is no dynamic recycling of the sample. When
there is continuous flow with at least one dwell time, the sample
is stopped and held for a certain length of time at the grating
location on the optical fiber. Continuous looping of a sample
involves moving the sample within the sample channel in such a way
that the sample is exposed to the grating on the optical fiber
multiple times in a circular or looping configuration such that the
sample coming from the sample output is re-fed at the sample port.
Alternatively, a sample undergoing continuous looping can undergo a
certain dwell time within the sensing area before the sample is
re-fed at the sample port.
[0046] The samples employed in the present invention may be of any
type known to those of skill in the art. In particular, the sample
is selected from the group consisting of: a liquid sample, a gas
sample; and a complex sample. Combinations of these sample types
may also be employed. For example, a liquid sample and a gas sample
may be injected into two different sample ports and mixed in the
sample channel. A complex sample is defined as a sample that is
heterogeneous in composition. Examples of complex samples include
but are not limited to: whole blood; serum; grain mixtures;
slurries; milk; urine; saliva; and spinal fluid.
[0047] The flow cells of the present invention are used to conduct
measurement studies on a sample and the flow cell. When the flow
cell has no sample outlet, the sample is introduced into the sample
port, allowed to flow into each sample channel, and certain
characteristics of the sample and the flow cell are measured at the
point or points on the optical fiber where the grating is located.
After the measurements are completed, the sample is removed from
the sample channel through the sample port. Alternatively, if the
flow cell contains a sample outlet, the sample is removed through
the sample outlet. Various physical characteristics of the sample
are measured such as temperature, pressure, refractive index, and
pH. These characteristics are based on the relationship of the
sample to that of the portion of the flow cell where the optical
fiber grating is located.
[0048] Alternatively, the flow cells of the present invention are
used to measure chemical characteristics of a sample. These changes
are based on the actual chemical composition of the sample. For
example, the biochemical changes taking place in the sample may be
measured. In addition, the biological target concentration, pH,
reaction rates and chemical target concentrations may be measured
in a sample.
[0049] For example, the flow cell may also be used for kinetic
studies. Kinetic studies are conducted by treating the optical
fiber sensor with ligands that react with targets contained in the
sample over a certain time period. The interactions provide
information about K.sub.d and K.sub.a coefficients. The flow cell
described herein can be used to establish the kinetic binding
values of rate of association (K.sub.on), rate of dissociation
(K.sub.off), and calculate the equilibrium dissociation constant
(K.sub.d). The following model is used to illustrate the
relationship between the values: 1
[0050] The interaction of the receptor, which is immobilized on the
fiber, and the ligand results in a receptor-ligand complex. The
rate of this complex formation is the rate of association or
K.sub.on rate. The formed complex can also dissociate to the free
receptor and ligand which is the rate of dissociation or K.sub.off.
When equilibrium is achieved the rate of association is equal to
the rate of dissociation and is referred to the equilibrium
dissociation constant (K.sub.d) and is defined by the ratio
K.sub.off/K.sub.on. When the concentration of ligand equals the
K.sub.d, half the receptors will be occupied at equilibrium. If the
receptors have a high affinity for the ligand, the K.sub.d will be
low, as it will take a low concentration of ligand to bind half the
receptors.
[0051] FIG. 12 depicts how a flow cell array is integrated with
other processes. This integration is useful for lab-on-a-chip type
applications. In this embodiment, a flow cell array 125 is
integrated with other processes on a chip. Multiple fiber optic
grating sensors 130 are in contact with at least one sample channel
135 to form the sensing area 140. An optical fiber connector 145 is
disposed on one end of the optical fiber grating sensors 130.
EXAMPLES
Example 1
[0052] A Protein A coated sensor was prepared by providing a glass
fiber having a long period grating (LPG) disposed therein. The
glass fiber was cleaned with a solution of methanol and
hydrochloric acid in a 1:1 mixture for one hour at room
temperature. The fiber was rinsed with methanol. The fiber was
soaked in a 10% solution of (3-Glycidoxypropyl)trimethoxysilane in
methanol for one hour at room temperature. The fiber was then
rinsed with methanol. Next, the fiber was soaked in a phosphate
buffered saline solution, pH 7.4 containing 100 ug/ml Protein A for
one hour. The fiber was rinsed with phosphate buffered saline
solution, pH 7.4 and stored in the same buffer at 2-8 degrees
C.
Example 2
[0053] The Protein A coated sensor of Example 1 was used to monitor
the response of the sensor to rabbit IgG. The Protein A coated
sensor was exposed to a phosphate buffered saline solution, pH 7.4,
(PBS) to establish a baseline signal for the sensor. The sensor was
then exposed to varying concentrations of rabbit immunoglobulin
(IgG, Technical grade available from Sigma) in PBS pH 7.4. As shown
in FIG. 13, the rabbit IgG bound to the protein A on the surface on
the fiber sensor. The magnitude of the response was dependent upon
the concentration of rabbit IgG. To remove any unbound material
from the sensor surface, the fiber was exposed to PBS pH 7.4. Next,
the fiber was exposed to 10 mM HCl to remove the bound IgG material
from the Protein A and to regenerate the fiber for a subsequent
assay cycle. Lastly, the fiber was exposed to a PBS pH 7.4 buffer
solution to re-establish a baseline and return the sensor to a
buffered environment.
[0054] Testing for this example took place in a single channel flow
cell with multiple repetitions. The flow cell configuration
consisted of a 3 part flow cell shown in FIG. 1. The flow cell
overall dimensions were [60 mm length.times.26 mm width.times.12.6
mm height]. The sample channel was 1 mm outer diameter throughout
the flow cell. The long period grating (LPG) sensing element was 1
mm long with a 125 micron outer diameter. The substrate holder that
housed the optical fiber channel holder had a sampling window that
was 1 mm wide.times.13 mm long. The substrate holder was 0.5 mm
thick. By changing the sensing element surface area and varying the
flow cell dimensions, smaller volumes can be achieved during
testing.
[0055] The above description and drawings are only illustrative of
preferred embodiments which achieve the objects, features and
advantages of the present invention, and it is not intended that
the present invention be limited thereto. Any modification of the
present invention which comes within the spirit and scope of the
following claims is considered part of the present invention.
* * * * *