Measuring and testing – Gas analysis – Solid content of gas
Reexamination Certificate
2002-11-04
2004-09-28
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Gas analysis
Solid content of gas
C073S028020, C073S028040, C073S028050
Reexamination Certificate
active
06796164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates generally to diverse fields impacted by the nature of molecular interaction, including biology, chemistry, medicine and diagnostics. More particularly, this invention is directed to a miniaturized integrated system for analyzing airborne biological particles and microorganisms.
2. Description of Related Art
Obtaining accurate measurements of the particle and gas content in diverse environments including the earth's atmosphere is important for monitoring and understanding such environments. Detection of biological warfare agents, collection of industrial pollutants in ambient air and fluids and sampling the same, collection of infectious or disease-causing organisms in closed and open spaces, as well as collection of radioactive particles or toxic vapors are just a few examples illustrating application of a system for analyzing biological particles and microorganisms.
The detection of low concentrations of aerosolized particles, i.e., particles suspended in air, generally requires that the particles be extracted from a large volume of air in order to capture a sufficient number of particles to exceed a detection threshold of a detection technique. For example, it is not uncommon to require the detection of aerosol concentrations of less than one hundred particles per liter of air. Typically immunoassay-type systems require approximately 100,000 organisms to achieve a successful detection. Obtaining this result from low concentrations can require particle extraction from over 1500 liters of air. Completion of this task in a timely manner (several minutes) requires that large volumes of air be processed.
Much effort has been expended in the past in the detection and classification of particles or aerosols in fluid streams. Impactors have been used for collecting aerosol particles for many decades. In the earliest embodiments, a stream of fluid containing the particles was accelerated toward an impactor plate. Due to their inertia, the particles hit the impactor plate and were collected there while the fluid was deflected to the side. With these types of impactors, only heavy particles were collected while particles below a certain “cut size” were carried away by the fluid stream.
However, a significant cause of inaccuracy in such impactors results from the deposition of particles on surfaces of the impactor other than the intended collection surfaces. This phenomenon reduces the accuracy of measurement of total particle mass concentration and of the size-fractionation of particles, since such losses cannot be accurately estimated for aerosols having varying size, shape, or chemistry. Additionally, particles may either reenter the fluid stream or bounce from the impactor's collection surface upon impact.
Another method for the detection and classification of particles is based on removing aerosolized particles from fluid streams by centrifugal force. This method is usually referred to as a “cyclone.” In accordance with this method, the aerosol is drawn into a cylindrical chamber so that the air makes one or more rotations inside before leaving the chamber through a tube at its center. Particles with sufficient inertia move centrifugally toward the inner wall.
A detection system associated with the cyclone principle of operation collects airborne particles from large volumes of air and concentrates the collected particles in a small volume of fluid. This fluid then can be inserted into a detection device such as an immunoassay cartridge to determine if a specific biological organism or agent is present. A schematic of such a system is shown in FIG.
1
.
In the shown system, air is drawn into a liquid-impinging system
10
such as a wetted wall cyclone or other sample collector
12
. As the air moves in a circular path, the water level rises, and particles impacting upon the surface of the sample collector
12
are captured in the fluid while the particle-free air exists out via the top of the jar. The fluid with captured particles is further transported for analysis by means of valves or pumps
14
. Systems intended to detect harmful biological agents require the delivery of the sample fluid to an array of immunoassay cartridges so that multiple analyses may be performed. Typically, the sample collector provided with an impinger nozzle is located a substantial distance from a multiplicity of tickets, each of which typically carries only an array of immunoassay strips. To couple the collector
12
with the selected ticket, the latter is moved to a location to be connected to the collector
12
via a pump
14
and a system of valves providing sample flow into the strips of the connected ticket. Once the strips are filled, the ticket is again displaced a substantial distance toward a detector
22
, which is configured to detect harmful agents. Upon completion of a positive detection, the remaining contents of the sample collector
12
, if any, are drained. A large volume cleaning solution reservoir
18
is then coupled to the collector
12
and to the sample-solution conveying parts, such as, for example, the fluid transfer pump and coupling lines, to clean and prepare them for a subsequent test; once the cleaning stage is completed, the contaminated solution is accumulated in a large-volume waste basin
20
.
Thus, the present technology requires that fluid from a single collection be transported a long distance to the detector. Before a new sample can be collected, analysis of the previous sample must be completed and the fluidics cleaned to prevent cross contamination. This process limits the maximum rate at which samples can be processed and amounts to a process that lasts about fifteen minutes.
Only after minimizing the possibility of cross-contamination, a new volume of the liquid is supplied from a collector supply
16
into the sample collector
12
to provide a trap for a new portion of particles entering the collector along with incoming air stream. To preserve tested samples for further consideration, a multiplicity of storage reservoirs
24
can be filled upon the completion of each test.
Thus, to summarize above, there are several significant disadvantages to this approach. First, transfer of the collected fluid to the detector is very complicated for multiple use systems. Second, between each analysis cycle the system must be purged to reduce cross contamination, requiring additional time and consumables. Third, the long fluid paths and complicated valve systems increase the likelihood of the system clogging due to environmental contaminants. Finally, in cold weather, significant power is required to prevent the fluids in the system from freezing.
It is, therefore, desirable to provide a simplified system for detecting aerosolized biological particles that requires fewer fluid-containing and fluid-conveying components and minimizes efforts directed to coupling these components for conducting a multiplicity of sequential tests.
SUMMARY OF THE INVENTION
To attain this, the present invention provides for a new configuration of a particle or sample collection and detection component, further referred to as a ticket, which includes, in addition to a cartridge provided with a row of immunoassay strips, a combination of an impinging nozzle, and sample reservoir. Optionally, a cleaning solution storage or reservoir can be an integral part of the inventive ticket. Thus, the inventive ticket is an integrated structural unit including a sample capturing and accumulating system, a cleaning system and a detecting system.
One of the advantages of the inventive ticket is the minimization of all fluid paths. Indeed, placement of a sample reservoir practically adjacent to a row of strips substantially reduces the distance which the sample solution travels between these components. Furthermore, by optionally providing each individual ticket with cleaning fluid or a solution reservoir, the system eliminates long cleaning-solution paths and obviates the need for a large-volume single cleaning fluid reservoir as
Carlson Micah A.
McLoughlin Michael P.
Cooch Francis A.
Larkin Daniel S.
The Johns Hopkins University
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