Patent Application
20100313686
1. Field of the Invention
The present invention relates to surface samplers. More specifically, the present invention relates to two dimensional and three dimensional surface samplers for bioterrorism particle detection.
2. Background of the Invention
In today's world, there has become an increased interest and understanding in contaminants that rest or reside on surfaces of virtually everything that comes into contact with humans. These include contaminants on food or counter surfaces, door handles, shopping cart handles, and countless other surfaces which are frequently in contact with human hands or bodies. Nowhere is such interest more pronounced than in the field of bioterrorism particle detection. Such contaminants are typically biological in the form of viruses or bacteria or other harmful particles. To that effect, a number of surface sampling procedures have been developed to test for contamination and other surface pathogens that may be present on a variety of surfaces.
Most conventional surface sampling has been conducted using swabs, wipes or cloth. In some instances, filter material is used for swabbing. Most result in a sample that is picked up on a moistened surface and must be extracted into a liquid for analysis.
In most common tests, cotton swabs (e.g., Q-tips) are used to sample the surface, then the swabs are placed into a tube. Next a conventional procedure is followed to recover particles from that sample into a liquid. Once in liquid, there is an attempt to identify what is collected from that surface via analysis through viable culture, PCR or other methods.
Although such conventional techniques are useful, they are not without their problems and limitations. There are a number of problems with conventional techniques, a main problem being a very limited surface sample. Further, the removal efficiency is low from certain surfaces, and the results are also very dependent on how careful the user is in terms of swabbing the surface.
Further common testing techniques include use of a sponge, or sponge-type surface sampler. The sponge is used to swab the surface, and is about a few inches in diameter so it allows the collection from a larger surface area. The sponge may be used dry or wet. In some techniques, there is a bottle associated with the backside of the sponge which squeezes the liquid through it and draws the collected particles out from that surface and typically into a collection sample bottle, which is then sealed for transport and analysis. One of the primary disadvantages of this sponge technique is that there is lower efficiency from recovering the particles from the surface using the sponge and lower efficiency for recovering the particles back out of the sponge (which naturally has cells in which particles may imbed within). Again, like the swab method, there is a lot of potential variability due to how the user does the extraction from the surface and the extraction from the sponge.
Other conventional techniques used for surface sampling include a large and heavy pressure washing system using a showerhead-like wand which sprays a liquid from a center nozzle and then collects the liquid in a ring of apertures around a peripheral surface of the wand. The jet from the surface is allegedly able to remove particles from the surface which are then drawn up through a vacuum port which goes into the collection container. Although with its advantages, the spray system is extremely heavy (approximately 200 pounds), and is difficult to move freely, and is dependent on the volume of liquid sprayed onto the surface and subsequently collected by the vacuum.
What is needed is an efficient and effective system, device, and method to test the two or three dimensional surface of virtually any object, and subsequently collect the samples from the surface in a manner which produces high concentration of surface sample product. The system, device, and method should be simple to use and administer, inexpensive to manufacture, and effective at collecting and sampling from any surface.
The present invention relates generally to the fields of bioterrorism security, medicine, food and beverage quality assurance and environmental science. Since the postal anthrax attacks of 2001 and the subsequent war on terrorism, many biothreat agent sampling and detection devices have been developed, and many new devices are now in development. In the field of bioterrorism defense and security, the invention described here can be used to sample surfaces during the threat assessment phase, and also to check for any remaining contamination following cleaning and decontamination efforts. The invention described herein can be used in conjunction with hazard assessment and critical control points (HACCP) planning and monitoring, and in field investigation for the sources of contamination on solid food items such as but not limited to spinach leaves, tomatoes, peppers, and pistachios. In the field of medicine, in particular pathology, samples taken from surfaces in surgical suites can help determine the effectiveness of cleaning procedures. In the field of environmental science, field samples taken from surfaces in the course of biological studies or investigations may contain biological particles of interest. Where samples taken contain low concentration of particles of interest, concentration of such materials is advantageous, and the liquid sample resulting from sampling using this invention is amenable to concentration using conventional concentration methods available in the market. Further, the present surface sampling and concentration system is compatible with test particles, such as the Biological Particulate Matter Analogue disclosed in U.S. Pat. No. 7,179,596, which is incorporated by reference herein in its entirety, a DNA-tagged polystyrene microsphere packaged in a metered dose aerosol dispenser (marketed by Evogen, Inc., as the “BioSim”) for safely training and testing bioterrorism response and cleanup team procedures, food and beverage or surgical suite contamination scenarios, or performing environmental and epidemiological studies with regard to biological particles.
A novel surface and object sample extraction device, system and method are disclosed which use a “wet foam” method. The surface sampler and object extractor embodiments described herein offer significant advantages over previous methods of biological particulate matter samplers including swabs, wipes, sponges and spray wash methods described above. Like swabbing, wiping, sponging, and spray washing and the other known conventional methods, the present invention extracts the sampled particles from the surface being sampled prior to analysis, but with many advantages: 1) The liquid volume of the sample produced per unit area sampled is reduced because the wet foam used to extract the particles from the surface quickly collapses to a fraction of its original volume upon collection. 2) This method is more efficient at removing particles from the sampled surfaces, resulting in collected fluid with a proportionally higher concentration of target particles, allowing better detection in devices such as multi-well plate readers that utilize small input samples. 3) This device is much more readily adapted to automated systems than hand operated swabbing and sponging techniques 4) This surface sampling method enables the construction of smaller, lighter-weight portable surface to liquid samplers because the “wet foam” extraction fluid is supplied to the spray nozzle under gas pressure, rather than mechanical pumps. The only electrically powered circuit in the device, the vacuum sample pickup, can be battery operated. This enables the sampler to be easily carried up steps, ladders, taken to sampling locations by first responders, and operated for long periods of time without operator fatigue. In the backpack configuration discussed in this disclosure, the sampler can be carried by a person wearing full MOPP gear or other protective gear. 5) This surface sampling method allows a larger area to be sampled per unit time and per sample than swabs, wipes, and sponges because a larger volume of sampling fluid can conveniently be supplied by a rechargeable/refillable extraction fluid tank. This advantage improves the probability of detection. 6) Shear produced in the thin film of bubbles in the “wet foam” extracts particles more efficiently than other methods. 7) Use of added mechanical force such as megasonic or ultrasonic waves to increase shear can further increase sample extraction efficiency. 8) The suction wand of the surface sampler can be used to sample a large volume of standing liquid if it is present on the surface being sampled. 9) Fabric can be efficiently sampled because the wet foam spray penetrates the fibers with extraction fluid and the vacuum suction pulls a large fraction of the sample back out of the fibers. When the wet foam is applied to one side of the fabric or porous material and the vacuum is applied to the opposite side, collection efficiency is further improved for certain applications.
The present invention presents novel, rapid, efficient sample collection devices and methods that remove and capture particles, and especially biological particles, from surfaces into a liquid sample. The present invention was developed primarily for obtaining samples of biological contamination from environmental surfaces. The surfaces may be substantially flat (two dimensional), or contoured (three dimensional). Biological particles, as described here, include bacteria, viruses, and other microorganisms, and other particles of biological origin including nucleic acids, proteins, and toxins.
Collection of these particles as described here is advantageous for detection of target particles such as pathogens because capture in a liquid allows many detection and identification methods to be used. Detection of pathogens and spoilage organisms on surfaces is advantageous for the prevention of the spread of further contamination and resulting illness. Collection in a liquid also allows concentration of the captured particles into a small volume, which makes them easier to detect. Biological materials that are suspended or dissolved in the liquid are also captured and can subsequently be identified if desired.
In one exemplary embodiment, the present invention is a system for extracting particles from a surface. The system includes a source of pressurized liquid containing a liquid; a source of gas containing a liquid soluble gas, wherein the source of gas is connected to the source of pressurized liquid such that the gas is dissolved into the liquid; an extraction device including an outlet port wherein the pressurized liquid having gas dissolved therein is applied as a wet foam to a surface having particles thereon and an inlet port wherein the wet foam is extracted from the surface; and a liquid collection reservoir in connection with the inlet port, wherein the wet foam extracted by the inlet port is stored as liquid having particles therein within the collection reservoir.
In another exemplary embodiment, the present invention is a method for extracting particles from a surface. The method includes providing a source of pressurized liquid; providing a source of gas, wherein the gas is connected to the pressurized liquid such that the gas is dissolved into the liquid; applying a wet foam on the surface having particles, the wet foam formed by the gas dissolved in the pressurized liquid being exposed to ambient pressure; extracting the wet foam from the surface; and collecting the wet foam as liquid within a reservoir.
The present invention provides novel devices, systems and methods for collecting and measuring surface samples to combat possible bioterrorism in an efficient and effective manner. The present invention provides many advantages over conventional systems including, but not limited to, allowing the capture of surface particles with high sampling efficiency resulting in high concentrations in a relatively low volume of liquid.
The present invention uses a collection fluid previously developed by the inventors, and described in co-pending and co-owned U.S. Published Patent Application Serial Number US 2009/0101575, described herein and throughout this disclosure as “wet foam” and which application is incorporated by reference herein into this disclosure in its entirety. This novel collection fluid (“wet foam”) is created by dissolving a compressed gas in a chemically buffered fluid containing a foaming agent and subjecting the fluid to a pressure drop. Further details of the production of such wet foam is described in the above identified application and is incorporated by reference into the present disclosure.
The wet foam described above is applied from a pressurized tank to the surface to be extracted through a constricted nozzle, or orifice that applies the fluid with some force onto the surface within an area that is physically constrained such that the formed wet foam can then be picked up by suction and transferred to a sample collection vessel. This method of surface extraction enables the construction of a smaller, lighter sampling device than is possible using pumps to force extraction fluid onto the surface being sampled, since compressed gas is the pressure source instead of batteries, motors, and mechanical pumps. Additionally, wet foam surface extraction produces final samples with smaller final volumes than is possible with plain liquid.
Use of the wet foam with the present invention reduces the need of liquid volume to about one fifth of that with liquid alone, as used with other conventional systems, thus allowing one to collect surface particles into a much smaller volume. This is an important advantage as collection of particles of interest into a fifth of the volume provides the ability to detect about ⅕th the number of particles as compared to detection of particles from surfaces sampled with other “pure liquid” conventional surface sampler systems. Another advantage of the present invention is that since less volume liquid needs to be used, a higher spray force may be used, resulting in a greater particle sample release from the surface, without having to use additional liquid volume. Further, there are other advantages with use of the foam, one being that the foam is very viscous compared to an aqueous liquid. The increased viscosity allows it to sweep across the surface inside of the head acting as a solid slush sweeping across the surface rather than just turbulence at the point of impact, so it's effective at removing substances from a surface over a distance as it travels from the point of injection to the point of collection.
Use of the wet foam with the present system and method provides a novel, efficient and effective manner of obtaining samples from any surface. Such wet foam is created in part by pressurizing the liquid under carbon dioxide and then releasing it into the atmosphere's pressure. The gas is typically carbon dioxide, and once the foam gets exposed to atmospheric pressure, the gas escapes from the foam and the foam goes back into liquid again which allows the user to proceed onto the next step of analysis without having to deal with the foam at that point because it has already turned back to a liquid sample. The foam used in the current invention allows use of about 20% of the liquid volume than conventional systems, which percentage is dependent on the carbon dioxide pressure that the liquid is held under before it is released.
Although carbon dioxide is being used as the gas herein and through the examples in this disclosure, other gases may also be used, including but not limited to, nitrous oxide, argon or other inert gases. The reason that carbon dioxide is used is because it's very soluble in water at room temperature, thereby allowing the expansion of about five times in foam form, because at room temp and about 120 PSI, one volume of liquid can hold about five volumes of carbon dioxide.
The hand held wand or nozzle that is being used is shown in the examples as similar to a paint sprayer nozzle, so it actually spreads out the wet foam as a fan approximately an inch and a half wide, or less. The wet foam reacts with the surface for about an inch (maybe even a little more) before it's drawn up into a vacuum port. So the user slides it in one direction. When the invention is in use, the user starts out by placing the wand on the surface, turning on the vacuum pump, then turning on the spray nozzle and then starting pushing it in the direction of the spray nozzle, so essentially pushing the foam back up into the vacuum port.
Another novel aspect of the present invention allows for maintaining the sample collection viable itself, by collecting the sample in a cyclone system. This allows the user to have the particle laden fluid spinning around the outside edge of the interior of the cyclone such that the vacuum that picks up the collected foam is pulled without losing the sample through the fan or through the blower essentially. Conventional systems do not have this feature, and typically use a hydrophobic filter attached to a collection reservoir, such that the vacuum is pulled through the hydrophobic filter preventing loss of sample.
The disadvantages of this type of system is that the hydrophobic filters easily become blinded when too much fluid comes in contact with them and particles of interest are readily lost onto the filter surface. Thus, the present invention provides further improvements over the conventional systems.
Another advantage of the present invention is that to create the wet foam, a surfactant must be included in the liquid, and no filters are used. Conventional systems typically use a hydrophobic filter. Use of the cyclone in the present invention eliminates the need for use of a hydrophobic filter. Use of the surfactant increases the efficiency of the collection. It's possible that use of a surfactant in other conventional filter-based systems would clog up the system by wetting the filter and cause the vacuum flow through the system to stop. In one embodiment of the present invention a hydrophobic filter may be used in combination with the cyclone to eliminate the potential for aerosolization of potentially dangerous particles into the ambient air. In this way the cyclone acts as a liquid knockout upstream of the hydrophobic filter to eliminate the potential for liquid to reach the filter, thus removing the possibility of wetting out of the filter.
Considering the above described features and advantages, a more detailed analysis of the individual components of exemplary systems according to the present invention may be made. Such exemplary embodiments are presented in the accompanying drawings. For the following description, it can be assumed that most correspondingly labeled structures across the figures (e.g., 132, 232 and 332, etc.) possess the same characteristics and are subject to the same structure and function. If there is a difference between correspondingly labeled elements that is not pointed out, and this difference results in a non-corresponding structure or function of an element for a particular embodiment, then that conflicting description given for that particular embodiment shall govern.
The system 100 is operated by turning on the vacuum source 135 and then opening the wet foam valve 115 while holding the extraction wand 110 to the surface 150. The wand 110 is then moved forward 161 or backward at a moderate pace thereby scrubbing the surface with the foam 151 which is continuously picked up by vacuum source 135, which effects the vacuum on the sample reservoir 130 through conduit 136. The recovered fluid 112 is pulled through conduit 131 and captured into a sample collection reservoir 130.
The pressurized fluid reservoir 120 is used to hold a volume of an extraction fluid under a head pressure of a water soluble gas. Appropriate gases include, but are not limited to, carbon dioxide, nitrous oxide, and other water soluble gases. Head pressures are generally in the range of 20 psi to as much as 900 psi, or more preferably, in the range of 50 to 600 psi. The extraction fluid contains a surfactant, protein, or other foaming agent in a concentration sufficient to produce a high quality wet foam, but in a sufficiently low concentration so as to allow the foam to break down relatively quickly and to not be inhibitory to subsequent analysis. Foaming agent concentrations are highly dependent on the agent being used. Foaming agents include, but are not limited to, Tween 20, Tween 80, Triton X-100 (and other alternative Triton and Tween formulations), microbial and viral growth media, bovine serum albumin, and ovalbumin. Concentrations of Tween and Triton concentrations generally fall between 0.001% and 1.0%, and more preferably in the range of 0.01% and 0.5%. Combining foaming agents, such as Tween 80 and microbial growth media, are advantageous in some applications to increase efficiency and improve compatibility with analysis methods and for increasing target particle culturability. Buffer, including phosphate buffered saline, tris buffer, PBS, or other buffer to buffer against carbonic acid being formed (when exposed to carbon dioxide), may be added to the extraction fluid to maintain a relatively neutral pH. Without the addition of the buffer the fluid generally becomes acidic due to carbonic acid (when using carbon dioxide as the expansion gas). Salts, small particles, and other additives may also be added to improve the ability of the wet foam to extract surfaces, improve culturability, or improve compatibility with analysis methods.
In certain exemplary embodiments, the pressurized fluid reservoir 120 is precharged with pressurized fluid or alternatively it may contain an integral bubbler which is attached to a regulated gas cylinder to charge the fluid with a water soluble gas. In certain exemplary embodiments, the precharged reservoirs use a quick connect and can be readily attached or detached from the surface extraction system. A length of tubing 121 attaches the pressure reservoir 120 to the extraction wand 110. Within the extraction wand 110 a push button, toggle valve, or electronically controlled on/off valve 115 is used to start and stop the dispensing of the extraction fluid 122. A separate switch controls a HEPA filtered blower 135 that is used to capture the dispensed wet foam 151 into a cyclonic sample collection reservoir 130.
As shown in
The shape of body portion 313 may vary in different embodiments of the extraction wand. In extraction wand 310A, shown in
One of the many features and advantages of the present invention is that it is highly portable, as shown in the exemplary 15-20 lb portable system 400 in
Cleaning and decontamination of the sampler can be performed using standard procedures, including, for example, 3% hydrogen peroxide or 0.5% sodium hypochlorite (10% dilution of commercially available bleach) or other common means of disinfection.
The three dimensional extraction system shown as system 500 in
As one of the potential environments for facing potential bioterrorism contamination would be in an outdoor arena, the present invention may be equipped on standard military (or civilian) vehicles, including the system 700 shown in
In another exemplary embodiment of the present invention, a multi-surface sampling system may become standard equipment in standard issue military jackets or vests, as indicated in
The embodiments presented and described herein are designed to have modular components which can be easily changed or replaced without affecting other components within the system. For example, extraction wand 410 or testing chamber 670 may be easily replaced with another extraction wand or testing chamber, respectively, after a given sampling has occurred. This prevents cross-contamination while at the same time maintains cost-effectiveness as only components which need to be changed between testing are changed, as needed.
Another optional embodiment would enable the recycling of the extracted fluid such that when the extracted fluid is collected after having been exposed to a surface having particles, the particles are filtered out (using, for example, a hollow fiber filter) and the extracted fluid is then reused on the surface. The sampled particles are then extracted from the filter, further concentrating the sample for further improvement in the ability to detect them. This would allow a very large surface area to be tested with a given volume of extraction fluid without concern that the extraction fluid would run out as it is being collected by the extraction wand.
The embodiments of the device described herein were built using a clear acrylic cylinder, in a cyclone configuration, to catch the sample and reduce the possibility of target particles being lost through the vacuum blower and so that the process could be viewed directly. Passages were drilled in the acrylic to accommodate the liquid flow paths, and fittings were mounted to the ports for tubing connection. Other materials may also be used as would be appreciated by one having ordinary skill in the art after consideration of the present disclosure.
The present invention may be used in many specific fields in bioterrorism security, as can be appreciated by one having ordinary skill in the art after consideration of the present specification and accompanying drawings. Without limitation whatsoever, these fields include, but are not limited to:
A list of CDC category A and B bioterrorism agents are presented below and reflect a non-exhaustive list of particles which may be specifically detected by the present invention.
Category A diseases/agents include those for which the U.S. public health system and primary healthcare providers must be prepared to address various biological agents, including pathogens that are rarely seen in the United States. High-priority agents include organisms that pose a risk to national security because they can be easily disseminated or transmitted from person to person; result in high mortality rates and have the potential for major public health impact; might cause public panic and social disruption; and require special action for public health preparedness. Exemplary pathogens include, but are not limited, to Anthrax (Bacillus anthracis), Botulism (Clostridium botulinum toxin), Plague (Yersinia pestis), Smallpox (variola major), Tularemia (Francisella tularensis), Viral hemorrhagic fevers (filoviruses [e.g., Ebola, Marburg] and arenaviruses [e.g., Lassa, Machupo]).
Category B diseases/agents include the second highest priority agents which include those that are moderately easy to disseminate; result in moderate morbidity rates and low mortality rates; and require specific enhancements of CDC's diagnostic capacity and enhanced disease surveillance. Exemplary pathogens include, but are not limited to, Brucellosis (Brucella species), Epsilon toxin of Clostridium perfringens, Food safety threats (e.g., Salmonella species, Escherichia coli O157:H7, Shigella), Glanders (Burkholderia mallei), Melioidosis (Burkholderia pseudomallei), Psittacosis (Chlamydia psittaci), Q fever (Coxiella burnetii), Ricin toxin from Ricinus communis (castor beans), Staphylococcal enterotoxin B, Typhus fever (Rickettsia prowazekii), Viral encephalitis (alphaviruses [e.g., Venezuelan equine encephalitis, eastern equine encephalitis, western equine encephalitis]), Water safety threats (e.g., Vibrio cholerae, Cryptosporidium parvum).
A third category, Category C diseases/agents, are the third highest priority agents and include emerging pathogens that could be engineered for mass dissemination in the future because of availability; ease of production and dissemination; and potential for high morbidity and mortality rates and major health impact.
A list of secondary potential biological threat agents which can be sampled with the present invention include, but are not limited to: I. Viri/prions (Flaviviruses (Yellow fever virus, West Nile virus, Dengue, Japanese encephalitis, TBE, etc.), Hep A, B, C, Prions (CJD, BSE, CWD), Alphaviruses (VEE, EEE, WEE), Nipah virus, Rabies virus, Rhinovirus, Polioviruses, Hantaviruses Filoviruses (Ebola, Marburg, Lassa)); II. Bacilli (Mycobacterium tuberculosis, drug resistant, Mycobacteria other than TB, like C. leprae, Streptococcus pneumoniae, S. pyogenes, S. aureus, Clostridium tetani, C. difficile, Bacillus cereus, Coxiella brunette (Q fever), Francisella tularensis, Borrelia recurrentis, Rickettsia rickettsii, R. prowazekii, Shigella sonnei, Bartonella henselae, Yersinia enterolitica, Y. pseudotuberculosis, Neisseria meningitides, Legionella pneumophila, Burkholderia pseudomallei, Pasturella multocida); III. Other Pathogenic Microorganisms (Cryptosporidium parvum, Histoplasma capsulatum, Cryptococcus neoformans, Aspergillus niger); IV. Pathogenic fungi (Acremomium spp., Alternaria alternate, Apophysomyces elegans, Aspergillus terreus, Bipolaris spp., Bipolaris spicifera, Blastoschizomyces capitatus, Candida krusei, Candida lusitaniae, Cladophialophora bantiana, Cunnihamella berholletiae, Curvularia lunata, Exserohilum rostratum, Fusarium moniliforme, Fusarium solani, Hansenula anomala, Lasiodilodia theobromae, Malassezia furfur, Paecilomyces lilacinus, Paecilomyces bariotii, Penicillium marneffei, Phialemonium curvatum, Philophora parasitica, P. richardsiae, Ramichloridium spp., Rhizomucor pusillus, Rhizopus rhizopodiformus, Rhodotorula rubra, Sacchromyces cerevisiae, Scedosporium prolificans, Trichosporon beigelii (T. asahii), Wangiella dermatitidis.
The present invention is designed to collect particle samples from surfaces where the physical sizes of some agents and surrogates include, but are not limited to: Bacillus thuringiensis endospore—approximately 1 μm; Bacillus anthracis endospore—approximately 1 μm, Yersinia pestis—Gram negative rod-ovoid 0.5-0.8 μm in width and 1-3 μm in length, Yersinia rohdei—approximately 1 μm, Venezuelan Equine Encephalitis—70 nm (0.07 μm), Gamma-killed MS2—2 mD or about 25 nm (0.025 μm) (but will pass through a 300 kD pore size but is retained by a 100 kD pore size Wick and McCubbin-ECBC), Ovalbumin—45 kD or 6 nm (0.006 μm), Botulinum Toxoid A—150 to 900 kD or 10 nm to 70 nm (0.01 μm to 0.07 μm) (Normally published as 150 kD however some publications state that toxoid A can be released as complexes comprised of the 150 kD toxin protein along with associated non-toxin proteins and can therefore be released in 900 kD, 500 kD, and 300 kD forms, DNA—1000 Bp or 600 kD up to 15,000 Bp or 9 mD.
Many specific fields of use of the present invention exist in the medical field and include, but are not limited to: the above types of sampling and analysis are performed for the fields of medical research and diagnostics: in forensic medicine where toxins or venoms on surfaces or objects are the targets of analysis; in forensic medicine and criminal science where DNA or RNA or other identifying biological particulate matter are the targets of analysis; in operating rooms where sampling of biological particles from surfaces and objects is conducted to evaluate their sterility; in pharmaceutical manufacturing where biological contamination of facilities, including surfaces and objects is regulated by the US Food and Drug Administration.
Many specific fields of use of the present invention exist in the environmental studies field and include, but are not limited to: the following types of sampling and analysis are performed for the field of environmental study: in health effects research regarding the determination of health effects known to be caused by biological materials present naturally in the environment, in cleanrooms where surfaces and objects are monitored for cleanliness and to avoid bringing in objects that can become sources of contamination, sampling natural and man-made surfaces for determination or discovery of biological materials.
Finally, the present invention's use and effectiveness and the viability of the foam have been validated through numerous experiments. One such example is described here. Sample extraction from hollow fiber filters, as described in co-pending and co-owned U.S. Published Patent Application Serial Number US 2009/0101575 (which is incorporated by reference herein in its entirety into this disclosure), can be performed into a small volume using foam made from the extraction surfactant. This procedure removes particles into a small final volume of fluid formed when the “wet foam” collapses, while simultaneously enhancing extraction efficiency and allowing for greatly reduced sample volumes compared to collection of a sample from the same unit area using water or other non-foaming liquids. A small volume of liquid can be used to create a large volume of foam. Since the boundaries of the bubbles present in the foam must remain intact to remain a foam, the boundaries of the bubbles at the interface of the surface and the extraction foam must always be touching. As the foam proceeds through the confined space in the sampling head, it sweeps the concentrate through the device. When the foam is extracted from the device and collapses, the remaining product is a smaller volume of liquid than would ordinarily be collected with water or non-foaming liquid. This volume can be in a range of less than approximately 1 milliliter to 1 liter or more. The foam is created by the pressure drop at the dispensing nozzle, then injected into the sampling head where it is swept over the surface being sampled and into the vacuum collection port. Foam made using pressurized carbon dioxide has been shown in experiments to be compatible with collection of viable Bacillus atrophaeus and viable Bacillus anthracis var. Sterne spores, MS2 bacteriaphage, and DNA. A US Army Natick Research and Development Engineering Center report, Natick/TR-94/019, also indicates that Bacillus stereothermophilus spore suspensions in buffered carbonated solutions were not harmed, but that germination was inhibited. This inhibition was reversed upon plating for enumeration. It is also known that carbon dioxide inhibits the growth of many microorganisms. This fact has been exploited in preventing bacterial food spoilage in food by using modified atmosphere packing (MAP, e.g., Baker, R. C., et. al., 1986, Effect of an elevated level of carbon dioxide containing atmosphere on the growth of spoilage and pathogenic bacteria at 2, 5, and 13 C. Poult. Sci. 65: 729-737). Based on data contained in the referenced report, it is believed that storage of the extraction buffer under carbon dioxide pressure will preserve the extraction fluid from growth of contaminants. Further, since the foam generation method is driven by the evolution of gas from the dissolved state in the surfactant extraction fluid, it continues to generate new bubbles as old bubbles burst during passage though the sampling head. The energy of the bursting bubbles assists in extracting particles from the surface being sampled into the reduced-volume sample. The majority of the bubbles in the extraction foam burst soon after release from the sampling head, resulting in a much smaller volume sample, which is essentially liquid in nature.
The foregoing disclosure of the exemplary embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents.
Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.
This U.S. Utility patent application claims priority to U.S. Provisional Patent Application Ser. No. 61/268,385, filed Jun. 12, 2009, the content of which is hereby incorporated by reference in its entirety into this disclosure.
| Number | Date | Country | |
|---|---|---|---|
| 61268385 | Jun 2009 | US |
