Patent Application
20190381504
Embodiments of the present invention relate to the field of clinical diagnostic tools.
Whole blood is widely used in in-vitro diagnostic research. Blood tests can provide valuable information for clinical diagnosis and drug development. However, most blood is analyzed using the blood plasma or serum, because red blood cells and their constituent substances (blood cell containing components) can interfere with the measurement. Thus, separation of serum or plasma from whole blood is a typical preparation step for blood analysis.
Conventionally, serum or plasma separation is performed by centrifugation using commercially available bench-top devices. This process is laborious and time-consuming, and the integration of centrifugal systems in small point-of-care devices is challenging and size-limited. Hence, other separation techniques are under development which allow for integration into point-of-care devices. Such techniques are based on the principles of electro-osmotic flow, hydrodynamic separations, acoustic forces, dielectrophoresis and particle retention. The latter separation principle normally relies on asymmetric membranes, which block red blood cells from passing such a filter. Plasma filtration is a promising plasma separation method, but has many drawbacks or challenges to overcome. Drawbacks are related to filter/membrane integration, clogging, plasma re-collection from the membrane and undesirable filtering of biomolecules. Further, filtration is time consuming and blood with a high hematocrit has to be diluted.
Electro-osmotic flow and hydrodynamic separations principles are used for microfluidic devices with analyte volumes in the micro-liter range. However, such techniques exhibit less plasma separation efficiency than centrifugation-based techniques.
A method, apparatus, and system for sample separation via centrifugation are presented. The integration of centrifugation-based plasma separation in in-vitro diagnostic devices is challenging due to size limitations, integration issues and low cost fabrication. The centrifuge device presented herein allows for efficient separation of plasma from whole blood using small sample volumes. For example, sample volumes of less than 500 microliters can be used. In other examples, sample volumes between 500 microliters and 1000 microliters, or between 1000 microliters and 5000 microliters, can be used.
In an embodiment, a centrifuge device includes a housing, a chamber, a channel, and a cover. The housing includes a first port and a vent opening and is designed to rotate about an axis passing through a center of the housing. The chamber is defined within the housing and is coupled to the first port. A first portion of the chamber has a width that tapers between a first width at a first position and a second width at a second position within the chamber, the first width being greater than the second width. The channel is coupled to the second position of the chamber and arranged such that a path exists for gas to travel from the channel to the vent opening. The cover provides a wall that seals the chamber.
An example method is described. The method includes placing a sample into a centrifuge chamber via a first port, the centrifuge chamber being defined within a cylindrical housing. Next, the first port is sealed to prevent any leakage of the sample back through the inlet. The centrifuge chamber is rotated about an axis passing through a center of the cylindrical housing. The rotation causes a separation of the sample within the chamber, where a first portion of the sample moves into a first portion of the chamber that extends along a circumference of the cylindrical housing and a second portion of the sample moves into a second portion of the chamber that extends radially from the axis passing through the center of the cylindrical housing. The method continues with stopping the rotation of the centrifuge chamber and extracting the second portion of the sample via a second port.
In another embodiment, a system includes a centrifuge device, an actuator, and an extraction device. The centrifuge device includes a housing, a chamber, a channel, and a cover. The housing includes a first port and a vent opening, and is designed to rotate about an axis passing through a center of the housing. The chamber is defined within the housing and is coupled to the first port. A first portion of the chamber has a width that tapers between a first width at a first position and a second width at a second position within the chamber, the first width being greater than the second width. The channel is coupled to the second position of the chamber and arranged such that a path exists for gas to travel from the channel to the vent opening. The cover has a second port and provides a wall that seals the chamber. The actuator is coupled to the housing and rotates the housing about the axis. The extraction device is coupled to the cover and extracts a sample within the chamber through the second port.
The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments of the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.
Embodiments of the present invention will be described with reference to the accompanying drawings.
Although specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the pertinent art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present invention. It will be apparent to a person skilled in the pertinent art that this invention can also be employed in a variety of other applications.
It is noted that references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure or characteristic is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure or characteristic in connection with other embodiments whether or not explicitly described.
Some embodiments described herein relate to a centrifuge device used to separate small sample volumes of less than 500 μL, between 500 μL and 1000 μL, or between 1000 μL and 5000 μL. The centrifuge device may be oriented along a horizontal axis such that it revolves about the horizontal axis. In some embodiments, the centrifuge device is designed to be integrated with a larger diagnostic testing system, such as a test cartridge. The test cartridge integrates all of the components necessary to perform such tests into a single, disposable package. The test cartridge may be configured to be analyzed by an external measurement system that provides data related to the reactions that take place within the test cartridge. In an embodiment, the test cartridge includes a plurality of test chambers with a transparent window to perform optical detection with each test chamber.
In an example, sample port 104 receives liquid samples, though other sample types may be used as well. Sample port 104 may also be designed to receive a needle of a syringe in order to inject a sample into a chamber or fluidic channel within cartridge housing 102. Sample port 104 may also be designed to be compatible with commercial blood collection devices, such as those of the VACUTAINER™ family.
Test cartridge 100 also includes another sample inlet protected by a cover 108. Cover 108 is removable to allow access to the additional sample inlet. This sample inlet may be used to introduce samples that do not need to be centrifuged.
The description herein will focus more on the design and function of the centrifuge device. Further details about test cartridge system 100 may be found in co-pending U.S. application Ser. No. 13/836,845, the disclose of which is incorporated by reference herein in its entirety.
According to an embodiment, cylindrical housing 202 includes a rotating portion 216 that rotates around a hinged connection 217. Rotating portion 216 may swing open to reveal an input port 204 for placing a sample into centrifuge device 200. The sample may be placed through inlet port 204 using a syringe or any other suitable fluid transfer mechanism. Rotating portion 216 may include a raised structure 218 that is dimensioned to fit into inlet port 204 when rotating portion 216 is shut. Raised structure 218 may seal inlet port 204 from any leakage. Raised structure 218 may include, for example, a gasket design with a polymer tip to seal the opening of inlet port 204.
Any sample placed through inlet port 204 goes into a centrifuge chamber 206. Centrifuge chamber 206 includes a curved geometry designed to aid in the separation of the sample during centrifugation as explained in more detail with reference to
In an embodiment, a collection chamber 210 is coupled between vent channel 208 and vent opening 212. Collection chamber 210 may be provided to receive the sample through vent channel 208 as the sample fills centrifuge chamber 206. The centrifugation process may not work correctly if the sample does not fill, or substantially fill, centrifuge chamber 206. Bubbles may form if there is too much trapped air within centrifuge chamber 206. Thus, collection chamber 210 may act as a safeguard to collect the sample before it can leak out of vent opening 212.
In an embodiment, cylindrical housing 202 includes a sample indicator 214 that is designed to indicate to a user when centrifuge chamber 206 is full or nearly full with a sample. For example, sample indicator 214 may turn a specific color when centrifuge chamber 206 is full. Sample indicator 214 may be made transparent or semi-transparent allowing the user to perceive when the sample has completely filled centrifuge chamber 206.
Cover 222 may be placed over one side of cylindrical housing 202 to seal one or more of the chambers defined therein. According to an embodiment, cover 222 includes a coupling structure 224 to allow for a connection to a extraction device. The base of the coupling structure 224 includes a port (not shown in this figure) for extracting out the separated sample within centrifuge chamber 206. The extraction device may be a syringe or a portion of the test cartridge described earlier with reference to
During rotation of device 200, a relative centrifugal force (RCF) is taking effect. Collinear to the center of rotation, RCF is zero, and perpendicular to the rotation axis RCF is increasing by a value of:
where g is earth's gravitational acceleration, r is the rotational radius and ω is the angular velocity in radians per unit time. RCF is increasing when r is increasing and particles with a high density are accelerated with a higher force than particles with a lower density. Thus, over time during the rotation, the sample is separated into two phases: a denser phase separates into tail area 304 while a less dense phase separates into collection area 302. In the example of using a whole blood sample, the blood plasma separates into collection area 302 while the remaining red blood cells and any contaminates are separated into tail area 304.
The changing width of tail area 304 is designed to aid in draining the less dense material into collection area 302 during the rotation. The width at location ‘A’ of tail area 304 may be larger than the width at location ‘B’ of tail area 304, with the width tapering between locations ‘A’ and ‘B’. At or near location ‘B’ where the width has tapered to its lowest point, tail area 304 couples to vent channel 208 according to an embodiment. Vent channel is routed back towards the center of cylindrical housing 202 such that a shortest distance from the axis of rotation 226 to vent channel 208 is shorter than any point within centrifuge chamber 206 to axis of rotation 226. This design helps to ensure a stable position of the sample during centrifugation and passively works to prevent air bubbles from entering into centrifuge chamber 206 from vent opening 212.
Centrifuge chamber 206 may have a volume of less than 500 μL, less than 400 μL, or less than 300 μL. In one example, centrifuge chamber 206 holds a 250 μL sample of whole blood. After centrifugation at between 5,000 and 20,000 RPM for about 3 minutes, about 60-70 μL to about 100-150 μL, of plasma may be separated into collection area 302. Centrifugation may be performed at, for example, 10,000 RPM.
Following centrifugation, or during centrifugation after a given period of time has elapsed, the sample has separated into a less dense phase in collection area 302 and a more dense phase in tail area 304. At this point, extraction of the separate phases may be performed via an outlet port (not shown, but described herein with reference to
According to an embodiment, during the sample extraction process, the sample is drawn out of centrifuge chamber 206 through outlet port 402, and air enters into centrifuge chamber 206 through vent channel 208. During this operation, the increasing cross-section of tail area 304 helps to prevent bubbles from flowing into collection area 303 and displacing the liquid within collection area 303.
At block 602, a sample is placed into a chamber via a first port (e.g., an inlet port). The sample may be a mixture of varying density components, such as a blood sample that includes red blood cells and other particles, and less dense plasma. The sample may be placed into an inlet via a syringe or another more integrated fluidic delivery system (e.g., microfluidic channels). The inlet leads into a centrifuge chamber defined within a cylindrical housing, according to an embodiment.
At block 604, the inlet is sealed to prevent leakage of the sample during centrifuging. Sealing the inlet may be performed by snapping shut another part of the centrifuge device, such that the inlet port is plugged. Any other well-known sealing mechanism may be used.
At block 606, the chamber is rotated about an axis passing through the center of the cylindrical housing to centrifuge the sample within the chamber. In one example, the chamber is rotated at a speed of about 5,000 to 20,000 RPM. In one particular example, the chamber is rotated at a speed of 10,000 RPM. The chamber may be designed such that it curls around an outer edge of the centrifuge device as illustrated, for example, in
At block 608, the sample is separated based on the centrifugal force applied within the chamber during the rotation. As noted above, the geometry of the chamber also helps to keep the denser material of the sample within a first section of the chamber, and a less dense material within a second section of the chamber. In an embodiment, the first section of the chamber extends along a circumference of the cylindrical housing while the second section of the chamber extends radially outward from the axis of rotation passing through the center of the cylindrical housing.
At block 610, the rotation of the chamber is stopped. In one example, the rotation of the chamber at 10,000 RPM stops after about 3 minutes. An abrupt stop also forces the more dense material to collect in the first section of the chamber, away from the less dense material collecting in the second section of the chamber.
At block 612, the less dense portion of the sample is extracted via a second port (e.g., an outlet port). The outlet port may be positioned substantially above the second section of the chamber, such that extracting through the outlet port only extracts the less dense material from the second section of the chamber following centrifugation. The extraction may occur due to an applied pressure differential (e.g., a vacuum pressure) applied at the outlet port. A syringe may also be used to extract the less dense material following centrifugation.
According to an embodiment, method 600 is performed without stopping the rotation of the chamber to extract the sample (i.e., skipping block 610.) The outlet port may be substantially centered over the axis of rotation.
Other steps may be performed in addition to part of method 600. For example, if the centrifuge device is integrated into a test cartridge, some steps may involve disengaging the centrifuge device from a fluidic coupling mechanism to allow the centrifuge device to rotate freely. The centrifuge device may then be reconnected, following the centrifugation, to the fluidic coupling mechanism within the test cartridge to extract the sample.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.
Embodiments of the present invention have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.
The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.
The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application is a divisional of application Ser. No. 15/210,689, filed Jul. 14, 2016, and claims the benefit of U.S. provisional application No. 62/193,954 filed on Jul. 17, 2015, the disclosure of which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62193954 | Jul 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15210689 | Jul 2016 | US |
| Child | 16554152 | US |
