WO2020019195A1

WO2020019195A1 - Microbead-based separating gel

Info

Publication number: WO2020019195A1
Application number: PCT/CN2018/097045
Authority: WO
Inventors: Zhaoqiang Wang
Original assignee: Yantai Ausbio Laboratories Co., Ltd.
Priority date: 2018-07-25
Filing date: 2018-07-25
Publication date: 2020-01-30

Abstract

A tube (100) comprises a separating gel (132-10) with microbeads. A method for sample collection and sample processing. A centrifugation method for enhanced sample enrichment.

Description

Microbead-based separating gel

Field of the Invention

The present invention relates to the field of automated sample processing for diagnostics purposes. More particularly, the present invention is directed to enhanced and coherently designed reagents, equipment and methods to allow for automated sample processing for diagnostic purposes to enhance both sample throughput and diagnostic precision.

Background of the Invention

One of the key focus of reagent developers and diagnostic instrument manufacturers is reliability, sensitivity and specificity of tests. Early detection is an important counter-measure to mitigate the various risks associated with an infection. Erroneous results in identifying infected samples may be life-threatening for literally everyone exposed to the source of the sample or the samples of the source. Blood donors, laboratory personnel and blood recipients may be mentioned as examples.

Therefore, sample screening reagents are continuously improved and advanced screening technologies are further developed and adopted in diagnostic instruments to revamp said reliability and sensitivity. On the one hand, automated diagnostic instrumentation may increase reliability and sensitivity by integrating ever more functions in the diagnostic instruments to replace manual intervention so human errors are reduced and precision is enhanced. In addition, turn-around time of samples may be reduced because automated sample processing typically significantly increases sample throughput. On the other hand, reagent kit manufacturers strive for the capability to detect and measure health-associated biomarkers with increasingly specific, reliable and sensitive methods. However, in recent times there has been little advancement which was broadly applicable for routine clinical analysis at a reasonable cost and performance, and there are still many cases of pathogen detection failures every day.

Such detection failures are often due to the characteristics of the latent or occult phase of the pathogen lifecycle, in which the sample might be taken from the wrong source: Occult hepatitis B virus (HBV) infection (OBI) is, for instance, by definition “characterized by the persistence of HBV [deoxyribonucleic acid] (DNA) in the liver tissue in the absence of circulating HBV surface antigen (HBsAg) ” (c.f. J Hepatol. 2008; 49 652-7) .

It is well known in the art that sampling of whole blood are typically collected by venipuncture through a needle attached to an evacuated blood collection tube. Centrifugation splits the sample into its components, wherein the filter and/or density gradient medium may help splitting at least two of these components. The separate analysis of the split components increases the number of processing steps significantly, however, thanks to the purity of the samples components, the reliability and sensitivity of the screening may be greatly increased.

Conventional samples for conducting tests include plasma or serum, these are the major blood components that are easily accessible after separation from whole blood. Although plasma is a major reservoir for pathogen and current standard of practice for blood screening, recent published papers showed evidence that the cellular contents circulating in blood are also very useful in diagnostics. Typically, during latent phase or at an early phase of infection, it may not be possible to detect targeted serological markers in plasma because the analytes are not yet being released from the infected cells or the traces of analytes are beyond limit of detection (LOD) . For instance, viruses can either directly interact with platelets via a plethora of surface receptors, some pathogens such as the dengue virus (DENV) may enter platelet, and pirating within vesicles. Some pathogens, including the human immunodeficiency virus (HIV) , bind or wrap within extracellular vesicles (EVs) , such as exosomes and micro-vesicles. Moreover, traces of the HIV genome have been found in natural killer (NK) cells, mononuclear cells and mast cells. Hepatitis B and hepatitis C viruses (HCV) do not only infect liver cells, but also reside in peripheral blood mononuclear cells (PBMCs) . They can infect B cells and replicate therein. Thus, white cells, particularly PBMCs, are a pathogen key reservoir for replication as well as a potential infectious site during the pathogen latent period.

The cellular contents may also offer insightful information in tumor-related diagnostics. Blood can be separated into different fractions in order to enrich for tumor-associated biomarkers. Circulating tumor cells (CTCs) may provide genomic, transcriptomic, and proteomic information on the tumor. Tumor Educated Platelets (TEPs) may provide a valuable platform for pan-cancer, multiclass cancer, and companion diagnostics in both localized and metastasized cancer patients.

It is thus critical for the device manufacturers, laboratory test vendors, and clinical laboratory personnel to understand these pathogen-cell interactions as potential source of improvements during analytical laboratory testing. Plasma or serum as conventional targeted sample is apparently insufficient to establish a comprehensive and complete analysis that covers the entire pathogen lifecycle.

However, current routine clinical practices are yet unable to fully incorporate cellular analysis for both economical and practical reasons. An important reason is the challenge to extract the cellular content from regular evacuated blood collection tubes in a high throughput and automated fashion.

Typically, cell separator tubes including a filter are used and/or density gradient medium is added to the sample and the samples are centrifuged. For example, U.S. Patent 4,021,340 and U.S. Patent 4,333,564 describe the use of hydrophobic gel-like, inert compositions having thixotropic properties. Commercial products such as BD’s Vacutainer ^TM Cell Preparation tube (CPT) is expensive and cannot be processed in an automated procedure. Due to the shape of the tube, the enriched buffy coat layer is very thin, identification by camera is difficult and the pipette channels may be clotted due to the thick gel separator applied. In addition, the tube made glass material may also break, particularly when handled by robotics.

s. Moreover, pre-filled tubes comprising density gradient media have a limited shelf-life. Specifically, separating gels are used to cover a density gradient medium in a tube and to separate it from an upper portion of the tube, thus acting as a gel barrier and allowing the transport of the tubes and application of samples without initial disturbance of the density gradient medium. Alternatively, other separating means, such as mechanical or physical barriers are known in the art. During application, a sample, e.g. a whole blood sample, is added on top of the separating gel, and the tube is centrifuged in order to break the separating gel and to allow the sample components to be separated within the density gradient medium during centrifugation. However, in case the tube is stored for some time before use, e.g. several months, the separating gel ages and becomes denser, requiring a higher centrifugal force for breakage, or the separating gel cannot be broken at all. Accordingly, the conditions of using pre-filled tubes can vary considerably with extended storage time, ultimately leading to inaccurate results. Further, the separating gel typically has a density similar to the one of the density gradient medium. Accordingly, if a high-density medium is to be used, also a separating gel with higher density is required, which is even more resilient to break at low centrifugal forces. However, the application of such low forces may be required for certain types of samples.

Hence, there is a need for robust, stable reagents and affordable evacuated blood collection pre-filled tubes and associated processing systems that can be used in automated and effective blood content fractionation and extraction in routine clinical practice.

:...:. The present invention thus aims at overcoming the aforementioned shortcomings of the conventional reagents, equipment and methods.

Summary of the Invention

The present invention solves the shortcomings of the state of the art by suggesting a tube comprising a density gradient medium and a separating gel, a method of separating a density gradient medium by adding a separating gel, a continuous two-step centrifugation method, a method for automated sample processing and a method to produce the tube in accordance with the features of the independent claims. Preferred embodiments are defined in the dependent claims.

The present invention improves the previously known solution in that it provides a coherent design and the means for automation to make highly reliable and highly sensitive blood screening affordable. More details on the structure and the advantages of the coherent design of the separator equipment with regard to a cost-efficient automated screening procedure are described in the following.

Enhanced Tube for Sample Collection and Sample Processing

In a first aspect of the invention, a tube for sample collection and sample processing is provided.

The tube according to a first embodiment of the present invention comprises a volume of a density gradient medium in a lowest portion of the tube, wherein the volume of the density gradient medium is separated towards a portion above the lowest portion of the tube by a volume of a separating gel forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube, wherein the separating gel comprises microbeads.

The microbeads provided in the separating gel improve the shelf-life of the tube. It has been found that pre-filled tubes comprising a density gradient medium and a separating gel without microbeads age to a considerable extent over time. Specifically, the aged separating gel becomes denser and more resilient to breakage upon application of a centrifugal force. Accordingly, a sample loaded on top of the separating gel cannot enter the density gradient medium and cannot be processed in such tube. By adding microbeads into the separating gel, the separating gel generally requires less centrifugal force to break. Moreover, also less centrifugal force is required to break the separating gel of pre-filled tubes that are stored for a few months before use.

Non-limiting suitable materials to be used for the microbeads include stainless steel, magnetic, silica; these materials are insoluble and immiscible in blood and non-reactive therewith. The microbeads can also be made of other material, such as glass or ceramics, and/or one or more polymers, such as, for example, nylon, polytetrafluoroethylene (TEFLON (TM) ) , polystyrene, polyacrylamide, sepharose, agarose, cellulose, cellulose derivatives, or dextran, and/or can comprise metals. Examples of microbeads include, but are not limited to magnetic particles, plastic particles, ceramic particles, carbon particles, metal particles, particles of complex compositions, microfabricated free-standing microstructures, etc.

The density gradient medium may comprise Percoll, Ficoll, iodinated compounds such as Nycodenz, Hypague, Optiprep, or Metrizamide etc, and combinations thereof, such as Ficoll-Paque, Histopaque, Histoprep, Lymphoprep etc, and organic solvents such as silicone fluid.

In a second embodiment, the microbeads according to the first embodiment have a density equal to or above 1.5 g/ml.

In a third embodiment, the microbeads according to any one of the preceding embodiments have a density in the range of 1.8 to 2.5 g/ml.

In a forth embodiment, the microbeads according to any one of the preceding embodiments are of an essentially round shape, preferably with a diameter in the range of 0.4 to 1 mm.

The diameters of the microbeads are, in practice, not exactly of uniform size. For example, commercially available microbeads are not strictly homogenous and comprise a distribution of diameters. For example, the unwashed glass beads of

product number G9143, comprise a mesh size, wherein 90%of the microbeads are indicated to be within a range of 212 to 300 μm. For the purposes of the present invention, the exact distribution of the microbeads’diameters may vary, depending upon the desired application. Preferably, in one application, at least 50%of the microbeads have substantially the same diameter or a narrow distribution. In other applications, at least 60%, at least 70%, at least 80%or at least 90%of the microbeads of the microbeads have substantially the same diameter or a narrow distribution. Also, it is possible that 100%of the microbeads of the microbeads have substantially the same diameter or a narrow distribution.

In a fifth embodiment, the microbeads according to any one of the preceding embodiments are comprised in a concentration of about 10 to 50%, weight of microbeads per total weight of the separating gel, or weight of microbeads per total volume of the separating gel. The concentration is based on the total amount of the separating gel. Accordingly, a separating gel may be prepared which comprises, for example, 10 to 50 mg of microbeads, and 90 to 50 μl of the gel component.

In a sixth embodiment, the tube according to any one of the preceding embodiments is further characterized in that the density gradient medium has a density between 1.01 and 1.119 g/ml, more preferably between 1.077 and 1.083 g/ml.

In general, the density of the separating gel should be similar to the density of the density gradient medium.

In a seventh embodiment, the tube according to any one of the preceding embodiments is further characterized in that the volume of the density gradient medium is between 100 and 600 μl, preferably between 200 and 400 μl, and the volume of the separating gel is between 35 and 300 μl, preferably between 100 and 200 μl.

In an eight embodiment, the tube according to any of the aforementioned embodiments is manufactured by plastics injection molding. However, other manufacturing methods can also be applied.

In a ninth embodiment, the tube according to any of the preceding embodiments is, for instance, made of glass.

In a tenth embodiment, the tube according to any of the preceding embodiments may comprise an upper section, an intermediate section, and a lower section, wherein the upper section and the lower section are substantially of cylindrical shape, e.g. apart from manufacturing tolerances.

In an eleventh embodiment, the upper section has an inner diameter larger than an inner diameter of the lower section and the upper section has an outer diameter larger than an outer diameter of the lower section. The intermediate section is located between the upper section of the tube and the lower section, wherein a top of the intermediate section connects to a bottom of the upper section and a bottom of the intermediate section connects to a top of the lower section. An inner diameter and an outer diameter of the intermediate section decreases from the top to the bottom of the intermediate section of the tube. The tube exhibits a plurality of fastening means for fixing the tube in a tube rack. The plurality of fastening means is located on an outer surface of the intermediate section and the lower section. The fastening means thus guarantee precision and mechanical stability of the shape of the tube across its lifetime as well as stabilize the tube throughout the subsequent automated processing procedure.

In a twelfth embodiment, the intermediate section of the tube according to the first embodiment is of a tapered shape. This allows that a desired buffy coat layer can be easily harvested in the lower section of the tube. Pipetting in the buffy coat layer may be challenging because of clotting at the tip of the pipette, in particular if the viscosity of the separator gel in the tube is low.

In a 13 ^th embodiment, the plurality of fastening means in the tube according to any of the aforementioned embodiments has a plurality of longitudinally extending tube ribs for fixing the tube in the tube rack. This further improves the stability during the automated processing procedure.

In a 14 ^th embodiment, the outer diameter at the top of the intermediate section of the tube is substantially equal to the outer diameter of the upper section. The inner diameter at the top of the intermediate section is substantially equal to the inner diameter of the upper section.

In a 15 ^th embodiment, in the tube according to any of the aforementioned embodiments, the inner diameter at the bottom of the intermediate section is substantially equal to the inner diameter of the lower section. The outer diameter at the bottom of the intermediate section is substantially equal to the outer diameter of the lower section.

In a 16 ^th embodiment, the tube according to any of the aforementioned embodiments is further improved in that it provides for the plurality of tube ribs that may be spaced apart at equal distances.

In a 17 ^th embodiment, the tube according to the 16 ^th embodiment is further characterized in that the plurality of tube ribs consist of two tube ribs that are 180° apart from each other.

In an 18 ^th embodiment, tube according to any of the aforementioned embodiments is further improved in that the plurality of tube ribs extend along the whole length of the intermediate and the lower section.

In a 19 ^th embodiment, the tube according to any of the aforementioned embodiments is further characterized in that the outer diameter of the upper section is substantially equal to a distance ranging from an outer edge of a first tube rib of the plurality of tube ribs to an outer edge of a second tube rib of the plurality of tube ribs.

In an 20 ^th embodiment, as an example, the tube according to any of the aforementioned embodiments is further characterized in that the inner diameter at the top of the intermediate section of the tube is 10.5 mm, and/or the inner diameter at the bottom of the intermediate section of the tube is 6.5 mm, and/or a thickness of the tube ribs is 2.0 mm.

In an 21 ^st embodiment, the tube according to any of the aforementioned embodiments is further characterized in that the tube comprises a tube cap, wherein the tube cap is insertable into the upper section such that the tube cap seals the tube, and the tube cap is configured to be held against a force in an axial direction towards the lower end of the lower section of the tube such that the tube is pulled off the tube cap by said force.

In a 22 ^nd embodiment, the tube according to the 21 ^st embodiment is further improved in that the tube cap comprises a tube cap body and a tube cap plug. The tube cap plug may be inserted into the upper section such that the tube cap plug seals the tube. The tube cap body may be configured to be arranged around the upper section and to engage the tube cap plug. The tube cap body may further be configured to be held against a force in an axial direction towards the lower end of the lower section of the tube such that the tube may be pulled off the tube cap by said force.

In a 23 ^rd embodiment, the tube according to the 21 ^st or 22 ^nd embodiment is further improved in that the tube cap is pierceable by a needle such that an evacuated tube with the tube cap inserted into the upper section receives a sample through the needle pierced into the tube cap.

In a 24 ^th embodiment, the tube according to the 22 ^nd or 23 ^rd embodiment is further characterized in that the tube cap body has substantially the shape of a cylindrical tube. In such a case, an inner diameter of a lower portion of the tube cap body is substantially equal to the outer diameter of the upper section, and an inner diameter of an upper portion of the tube cap body is substantially equal to the diameter of the upper cylindrical bar of the tube cap plug.

In a 25 ^th embodiment, in the tube according to any of the 22 ^nd to 24 ^th embodiments, the tube cap body comprises at least two circumferentially protrusions to engage the tube cap and the tube cap plug. This may further reduce the risk of cross-contamination, since tube caps may remain fixed in their position, when the tube cap is fixed in a tube rack head.

In a 26 ^th embodiment, in the tube according to any of the preceding embodiments an inner surface of the tube above the gel barrier may be coated with an atomized anticoagulant. A maximum volume of the tube above the gel barrier and below the tube cap may be evacuated.

In a 27 ^th embodiment, the tube according to hany one of the preceding embodiments is further improved in that the tube cap and/or the density gradient medium and/or the separating gel of the tube are sterilized. Sterilization by Gamma irradiation may be mentioned as example.

.

In a further embodiment, the tube according to any of the aforementioned embodiments further comprises, as an example, an outwardly extending spherical ending for closing the tube at a lower end of the lower section of the tube.

Tube Rack

In a second aspect, a tube rack that is configured to receive one or more tubes according to any of the preceding embodiments is provided. In a first embodiment of the tube rack, the tube rack comprises a tube rack body comprising one or more tube holders. Each of the tube holders is shaped to seamlessly receive one of said tubes and comprises reception means to receive the plurality of fastening means located on the outer surface of the intermediate section and the lower section of the tube.

In a second embodiment of the tube rack, the tube holders comprise symmetrical trajectories to receive the plurality of fastening means.

In a third embodiment of the tube rack, the tube rack according to any of the aforementioned embodiments further comprise a wall to provide a structural rigidness, and a non-noise background allowing for automated content identification.

In a fourth embodiment of the tube rack, the wall of the tube rack according to the third embodiment of the tube rack comprises an opening to expose a front side of the tube.

In a fifth embodiment of the tube rack, the tube rack according to any of the aforementioned embodiments further comprises a separable tube rack head, wherein the tube rack head comprises one or more openings corresponding to the one or more of the tube holders. Each of the tube holders may comprise a protruding ring to align to a corresponding groove on an underside of each of the one or more openings of the separable tube rack head.

In a sixth embodiment of the tube rack, the tube rack head in the tube rack according to the fifth embodiment further comprises one or more clippers configured to engage in a recess on the tube rack body.

In a seventh embodiment of the tube rack, the tube rack according to any of the aforementioned fourth to sixth embodiments is further characterized in that each of the one or more openings of the tube rack head comprises a crown-shaped upper part, wherein each crown-shaped upper part comprises one or more inwardly extending bumps.

In an eighth embodiment of the tube rack, the tube rack according to any of the aforementioned fourth to seventh embodiments is further characterized in that the tube comprises the tube cap comprising the tube cap body and the tube cap plug, wherein the tube rack head is configured to capture the tube cap so that there is a gap between the lowest portion of the tube and a bottom of the tube rack body.

In a ninth embodiment of the tube rack, the tube rack according to any of the aforementioned fourth to seventh embodiments is further characterized in that the tube rack head is configured to capture the tube cap so that the lowest portion of the tube contacts a bottom of the tube rack body.

In a tenth embodiment of the tube rack, the tube rack according to any of the aforementioned embodiments is characterized in that the tube holders are arranged in two or more rows.

Method for separating a volume of a density gradient medium

In a third aspect, a method is provided for separating a volume of a density gradient medium comprised in a lowest portion of a tube. According to the present invention, the method comprises the step of adding a volume of a separating gel forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube, wherein the separating gel comprises microbeads.

As explained above, the presence of microbeads in the separating gel allows to form a stable gel barrier for the density gradient medium. The gel barrier can be broken during application by application of a low centrifugal force. Moreover, the stability of the gel barrier remains constant over time, such as over several months of storage.

The separating gel may be a separating gel as defined above.

The microbeads may have a density equal to or above 1.5 g/ml. The microbeads may have a density in the range of 1.8 to 2.5 g/ml. The microbeads may be of an essentially round shape, preferably with a diameter in the range of 0.4 to 1 mm. The microbeads may be comprised in a concentration of between 10 and 50%.

The density gradient medium may have a density between 1.01 and 1.119 g/ml, preferably between 1.077 g/ml and 1.083 g/ml.

The volume of the density gradient medium may be between 100 and 600 μl, preferably between 200 and 400 μl, and the volume of the separating gel may be between 35 and 300 μl, preferably between 100 and 200 μl.

The present invention also relates to the use of a separating gel comprising microbeads for separating a volume of a density gradient medium comprised in a lowest portion of a tube by forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube.

The separating gel and/or the density gradient medium may be as defined above with reference to the method for separating a volume of a density gradient medium comprised in a lowest portion of a tube.

Centrifugation Process for Enhanced Sample Enrichment

In a forth aspect, an enhanced continuous two-step centrifugation method for enhanced sample enrichment is provided. The tube is preferably of the configuration as described in any of the preceding embodiments. Moreover, the tube rack according to any of the aforementioned embodiments may be used for carrying out the continuous two-step centrifugation method for enhanced sample enrichment.

The centrifugation method comprises the steps of centrifuging for a first period of time at a first relative centrifugation force (RCF) . The first RCF is applied without changing a relative position of the density gradient medium in the tube to achieve an initial cell separation. In some embodiments, the first period of time is at least 10 minutes, and preferably at least 15 minutes. In preferred embodiment, the first period of time is in the range of 15 to 20 minutes, and the first RCF is in the range of 50 to 300 RCF, and preferably in the range of 100 to 200 RCF.

The centrifugation method also comprises performing further centrifuging for a second period of time at a second RCF. The second RCF may change the relative position of the density gradient medium in the tube. The second RCF may, for instance, be performed by accelerating to the range of 100 to 800 RCF, preferably in the range of 300 to 600 RCFg. In some embodiments, the second period of time may be at least 5 minutes preferably at least 15 minutes. In a preferred embodiment the second period of time is in the range of 15 to 30 minutes.

Preferably, the second RCF does not exceed 600 RCF. This ensures high quality of the separation method and sample enrichment.

In some embodiments, the centrifuging for a second period at a second RCF may be performed without stopping the centrifuging.

Automated Sample Processing

In a fifth aspect, the invention provides for a method for automated sample processing.

The automated sample processing method may in particular comprise the steps of

a) transferring, by means of a robot comprising a gripper, a tube rack comprising one or more tubes from a tray to a support located in a centrifuge,

b) applying at said centrifuge the continuous two-step centrifugation method,

c) after said continuous two-step centrifugation method, extracting, by means of the robot, the tube rack head from the tube rack body by grabbing the tube rack head such that the clippers disengage the tube rack body,

d) after said extraction of the tube rack head, extracting, by means of the robot, the tube rack body from the support of the centrifuge by grabbing the tube rack body.

The tube may be configured according to any of the preceding embodiments, the tube rack head according to any of the aforementioned embodiments of the tube rack head, and the centrifugation method may correspond to any of the aforementioned embodiments for the centrifugation method.

Manufacturing Process

In a sixth aspect, a method to produce the tube is provided. A tailored manufacturing process may be required to guarantee that manufacturing tolerances are met. The tube shall, for instance, be highly concentric. Eccentric tubes may cause varying volumes of samples collected in the tube, which may ultimately lead to inaccurate liquid handling after centrifugation.

Highly concentric tubes may be manufactured by locating at least two injection inlet channels in a molding form corresponding to the tube. The at least two injection inlet channels may be located equally spaced apart around a perimeter located at a top of the upper section to enable injection from an outer surface at the top of the upper section.

The method may further comprise vacuum sealing and aluminum packaging to prevent evaporation of density gradient medium prior to use. Vacuum sealing and aluminum packaging prevents shrinking and therefore helps maintaining the impermeability of the tube prior to use.

Detailed Description of the Preferred Embodiments

In the following, preferred embodiments of the invention are described with reference to the figures, in which:

Fig. 1 shows various views of a tube illustrating geometrical features of the tube according to an exemplary embodiment of the invention.

Fig. 2 shows further views of the tube including a tube cap according to an exemplary embodiment of the invention.

Fig. 3 shows various views of a tube rack including tubes and tube caps, according to an exemplary embodiment of the invention.

Fig. 4 shows an enlarged section of a longitudinal cut in a three-dimensional view of a part of the tube rack equipped with a tube and a tube cap, according to an exemplary embodiment of the invention.

Fig. 5 illustrates an exemplary embodiment according to the invention of a first step of the method for automated sample processing, in which a tube rack including tubes and tube caps is transferred, from a tray full of tube racks (left part of the figure) to a support located in a centrifuge (right part of the figure) , wherein the transferring is performed by means of a robot comprising a gripper.

Fig. 6 shows a various views of a centrifuge before centrifugation, according to an exemplary embodiment according to the invention. The centrifuge is fully equipped with tube racks (as described and illustrated in Fig. 5) . Sections A and B of Fig. 6 show enlarged sections of longitudinal cuts of the tube racks, when placed in the centrifuge. Sections A and B of Fig. 6 also illustrate that the tubes are closed in the tube rack before centrifugation.

Fig. 7 shows various views of a centrifuge during a second step of the continuous two-step centrifugation according to the invention, according to an exemplary embodiment. The centrifuge is fully equipped with tube racks (as described and illustrated in Fig. 5) . Sections A and B show enlarged sections of longitudinal cuts of the tube racks, when the centrifuging is performed in the centrifuge. Sections A and B of Fig. 7 also illustrate that the tubes are opened in the tube rack throughout the second step of the continuous two-step centrifugation.

Fig. 8 illustrates an exemplary embodiment of a second step of the method for automated sample processing according to the invention, in which a tube rack head (including tube caps) is extracted from the tube rack body (including tubes) such that the clippers disengage the tube rack body. Extracting is performed by means of a robot comprising a gripper. Various views are shown, in which the centrifuge is equipped with a tube rack body, in which tubes are opened (as described and illustrated in Fig. 7, sections A and B) .

Fig. 9 illustrates an exemplary embodiment of a third step of the method for automated sample processing according to the invention in which a tube rack body (including tubes) is transferred from a centrifuge of the figure) to a tray. Transferring is performed by means of a robot comprising a gripper. The tubes in the tube rack body are opened and tube caps are removed (as described and illustrated in Fig. 8) .

Fig. 10 illustrates an exemplary embodiment of the tube at four (A-D) specific stages in the life-cycle of the tube with focus on the state of some key features of the tube filled with a sample throughout automated processing.

Fig. 11 illustrates an exemplary embodiment of the tube packaging. The figure shows an assembled closed state (A) as well as an opened state (B, D) including the tube (C) for illustrating the relative arrangement of the parts (B, C, D) .

Fig. 12 illustrates an exemplary embodiment of the tube at three (A-C) specific stages and a reference example of a reference tube at three (B-D) specific stages during processing of a sample.

Fig. 13 illustrates an exemplary embodiment of the tube at two (A, B) specific stages and a reference example of a reference tube at three (A-C) specific stages during processing of a sample.

Fig. 14 illustrates an exemplary embodiment of the tube during processing of a sample (A) and a reference example of a reference tube during processing of a sample (B) .

Exemplary Embodiments of the Tube for Automated Sample Processing

Fig. 1 shows a first and second lateral view, a top view as well as a three-dimensional projection of an exemplary embodiment of a tube (100) according to the invention. The peculiar shape of the tube ensures that platelet and white cells (i.e. the immune cell reservoir) may reach the desired thickness for automated sample processing. Sampling may, for instance, conveniently be performed by pipetting through guidance via a CCD camera, determining layer positions with high precision and therefore maximizing the possible retrieval rate of the immune cell reservoir. In the present embodiment the tube comprises an upper (110) , an intermediate (120) and a lower section (130) and it is closed towards the lower end by a spherical ending (150) .

The upper section (110) and the lower section (130) are shown to be of substantially of cylindrical shape. The upper section (110) may have an inner diameter larger than an inner diameter of the lower section (130) and the upper section may have an outer diameter larger than an outer diameter of the lower section. The intermediate section (120) which is located between the upper section (110) of the tube and the lower section (130) may be of tapered shape. A top of the intermediate section (120) may connect to a bottom of the upper section and a bottom of the intermediate section may connect to a top of the lower section. An inner diameter and an outer diameter of the intermediate section may decrease from the top to the bottom of the intermediate section of the tube.

Fastening means, which in the present example are shown as tube ribs (140) , are located at the outer surface to stabilize the body of the tube and, more importantly, to guide and stabilize the tube when placed e.g. in a rack and centrifuged. As can be seen in Fig. 1, it is preferable that the tube ribs extend along the intermediate section (120) and the lower section (130) . The arrangement of the tube ribs is preferably symmetrical, 180° spaced apart from each other (in case two tube ribs are used) , and the shape may be such that they substantially extend in parallel to the longitudinal axes of the tube. Moreover, the shape may be such that the distance ranging from an outer edge of a first tube rib to an outer edge of a second tube rib substantially equals the outer diameter of the upper section (130) .

The tube may consist of the aforementioned parts, as exemplified in Fig. 1, or may also comprise further parts, such as for example additional fastening means.

A total height of the tube may, for instance, be 100 mm at a volume of approximately 4800 μl. A height of the upper section of the tube may, for instance be 25 mm. A height of the intermediate section (120) may be 16 mm while a height of the lower section (130) together with the spherical ending (150) may be 59 mm. One or several volume marks may be indicated on the tube. The tube may, for instance, be made of plastic or glass by molding or any other material and suitable manufacturing technique.

Fig. 2 shows a longitudinal cut as well a three-dimensional projection of an exemplary embodiment of the tube (200) including a tube cap (210) . The tube cap (210) comprises a tube cap body (220) and a tube cap plug (230) . The tube cap may be fastened on the tube (as shown) to seal the tube so that a vacuum in the tube may persist. The tube cap may be pierced by a needle such that an evacuated tube with the tube cap plug inserted into the upper section may receive a sample through the needle pierced into the tube cap plug. The tube cap plug may also seal the tube. The tube may comprise one or more contents (not shown in this figure; shown in Fig. 10) . According to the present invention, the tube comprises a volume of a density gradient medium (c.f. (131-10) in Fig. 10) in a lowest portion of the tube. Type of suitable density gradient medium include, but are not limited to: Percoll, Ficoll, iodinated compounds such as Nycodenz, Hypague, Optiprep, or Metrizamide etc, and combinations thereof, such as Ficoll-Paque, Histopaque, Histoprep, Lymphoprep etc, and organic solvents such as silicone fluid. The volume of the density gradient medium (c.f. (131-10) in Fig. 10) is separated towards a portion above the lowest portion of the tube by a volume of a separating gel (c.f. (132-10) in Fig. 10) forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube. The gel barrier facilitates stable storage and transportation of the tube, in order to prevent intermixing (dilution) of sample and density gradient medium prior to centrifugation. As an example, the density gradient medium may have a density between 1.01 and 1.11 g/ml, or between 1.077 and 1.083 g/ml. The volume of the density gradient medium in the tube may be between 100 to 600 μl, preferably between 200 and 600 μl, 300 to 600 μl, 400 and 600 μl, 500 to 600 μl and e.g. 450 μl. The volume of the separating gel in the tube may be between 35 to 300 μl, e.g. preferably 100 to 200 μl. An inner surface of the tube above the gel barrier may be coated with an atomized anticoagulant. A maximum volume of the tube above the gel barrier and below the tube cap plug may be evacuated. The tube, the tube cap and the contents of the tube, i.e. the density gradient medium and the separating gel, may be sterilized. Sterilization by Gamma irradiation may be mentioned as example.

In one embodiment, silicone fluid is used as density gradient medium (c.f. (131-10) in Fig. 10) in the lowest portion of the tube. Also, there might be no need for vacuum sealing or aluminum packaging (described later) to prevent evaporation of the density gradient medium prior to use.

Fig. 3 illustrates a tube rack according to an exemplary embodiment of the invention. The tube rack (310) is shown in a longitudinal cut, in a lateral view, in a top view as well as in a three-dimensional perspective, wherein the tube rack is shown with tubes and tube caps inserted (together referred as 300) . The tube rack is (310) may comprise a tube rack body (320) including one or more tube holders (330) as well as a tube rack head. The tube rack head (340) is fixed to the tube rack body (310) by means of clippers (341) configured to engage in a recess or the like on the tube rack body. Each tube holder has an opening (331) exhibiting the contents of the tube towards the environment of the tube rack. A wall at the opposite of the opening of each tube may act as a low-noise background for automated content identification (e.g. for a level detecting CCD camera) . The wall provides also structural rigidness for the tube rack, in particular for the tube rack body.

As may be seen in the part of the figure showing the tube rack from a longitudinal cut, when the tube cap is plugged and sealing the upper section of the tube and when the tube is placed in one of the tube holders, the tube cap may capture the tube so that there is a gap between the lowest portion of the tube and a bottom of the tube rack body. In the exemplary embodiment show, this is possible because the tube cap rests on the tube rack head. A centrifugation force in an axial direction towards the lower end of the lower section of the tube may thus pull the tube off the tube cap (or vice versa) . When the tube is pulled of the tube cap, the tube is sliding in the tube holders towards a bottom of a tube rack. The sliding motion of the tubes is controlled by the tube ribs, which are guided by symmetrical trajectories (c.f. Fig. 4 for an illustration of this feature) in the tube rack body. The tube is opened when a lowest portion of the tube contacts the bottom of the tube rack body.

Fig. 4 shows an enlarged section of a longitudinal cut in a three-dimensional view of a part of the tube rack equipped with a tube and a tube cap (together referred to as 400) , according to an exemplary embodiment of the invention. A tube cap (210) may be plugged into the upper section of the tube (110) . The tube cap body (220) may comprise a circumferential protrusion (221-4) to engage the tube cap plug (230) . Another circumferential protrusion may engage the tube cap body against the tube rack head (340) , i.e. the tube rack body (320) , i.e. against the centrifugation force in an axial direction towards the lower end of the lower section of the tube may, which may pull the tube off the tube cap. The tube cap plug may seal the tube. In one example, the tube cap plug may be punctured by a needle such that a sample is pulled in the tube by the vacuum in the evacuated tube.

As is shown in Fig. 4, the tube cap may fit smoothly into a crown-shaped upper part (343-4) of the tube rack head, in which it may be fixed by an inwardly extending bump (344-4) . The tube rack head, in turn, may fit smoothly onto the tube rack body. Protruding rings (333-4) above each tube holder (330) may fit smoothly to the groove (342-4) of the tube rack head such that the tube rack head (and hence the tubes) are fixed in their positions. Clippers (341) may fix the tube rack head to the tube rack body, which, for instance, helps minimizing the risk of cross-contamination during centrifugation. Cross-contamination is also mitigated by the fastening means located on parts of the outer surface of the tubes, which were for example shown as tube ribs 140 in Figs. 1 and 2. These tube ribs help stabilizing the tube during centrifugation and guiding the tube along the symmetrical trajectories when it is being opened, i.e. when it is sliding downwards (in the direction of the lower section of the tube) . An upper portion of a symmetrical trajectory is shown in Fig. 4.

Fig. 5 illustrates a first step of the method for automated sample processing according to the invention. In this step, a tube rack that may be of the type set forth above in the exemplary embodiments of the invention, including one or more tubes, which may also be of the type as set forth above in the exemplary embodiments of the invention, is transferred from a tray to a support location in a centrifuge. The transferring is performed by means of a robot comprising a gripper.

As shown in Figure 5, the tube rack (310) includes tubes and tube caps. By means of the robot comprising the gripper (530) , the rube racks are easily transferred from a tray full of tube racks (520, shown in a three-dimensional view on the left) to a support (540) located in a centrifuge (530, shown in a three-dimensional view on the right) .

Fig. 6 shows various views of a centrifuge before centrifugation, according to an exemplary embodiment according to the invention. The centrifuge is fully equipped with tube racks as has been illustrated in Fig. 5 and described above. Sections A and B of Fig. 6 show enlarged sections of longitudinal cuts of the tube racks, when placed in the centrifuge. Sections A and B of Fig. 6 also illustrate that the tubes are closed in the tube rack before centrifugation.

More particularly, section A of Fig. 6 illustrates that the tubes are closed in the tube rack before centrifugation as detailed in Figs. 3 and 4. The tube cap body (220) may rest on the tube rack head and hold the tube cap plug (230) by means of a circumferential protrusion (221-4) . The tube rack head may, in turn, rest on the protruding rings (333-4) above each tube holder. The clippers may fix the tube rack head to the tube rack body. Section B illustrates that there is a gap between the lowest portion of the tube and a bottom of the tube rack body. Symmetrical trajectories (334-4) may receive the tube ribs to stabilize the tubes in the tube rack (i.e. the tube holders) and guide their opening movement during centrifugation.

Fig. 7 shows various views of a centrifuge during a second step of the continuous two-step centrifugation according to the invention, according to an exemplary embodiment. The centrifuge is fully equipped with tube racks as has been illustrated in Fig. 5 and described above. Sections A and B show enlarged sections of longitudinal cuts of the tube racks, when the centrifuging is performed in the centrifuge. Sections A and B of Fig. 7 also illustrate that the tubes are opened in the tube rack throughout the second step of the continuous two-step centrifugation.

More particularly, as is shown in Fig. 7, the tube racks are placed in the support. Section A illustrates that the tubes are opened in the tube rack throughout the second step of the continuous two-step centrifugation when the sealing force is smaller than the centrifugation force. The tube cap body (220) may rest on the tube rack head and hold the tube cap plug (230) by means of a circumferential protrusion (221-4) . The tube cap plug may be moved out of the upper section of the tube (110) . The tube rack head, in turn, may rest on the protruding rings (333-4) above each tube holder. The tube caps may remain fixed in the tube rack head (340) in its crown-shaped upper part in which bumps (c.f. Fig. 4) fix the tube caps to the tube rack head. The tube may slide towards the bottom of the tube rack until the spherical ending (150) was stopped at the bottom of the tube rack. The sliding movement may be guided by symmetrical trajectories receiving the tub ribs (140) for each tube.

The continuous two-step centrifugation serves for enhanced sample enrichment and minimize cell loss in a tube. In general, larger and denser particles sediment at lower centrifugal force, and smaller and less dense particles fractionate at very high centrifugal force. When red blood cells in whole blood are aggregated, some cells are trapped in the clumps and therefore sediment with the red blood cells. This tendency to trap cells may be reduced by the adoption of continuous two-step centrifugation method without the need to pre-dilute the sample. Said method particularly comprises the steps of:

- centrifuging for a first period of time at a first relative centrifugation force (RCF) without changing a relative position of the density gradient medium in the tube to achieve an initial cell separation, wherein the first period of time is at least 10 minutes, preferably at least 15 minutes and most preferably in the range of 15 to 20 minutes, and the first RCF is in the range of 50 to 300 RCF, and most preferably in the range of 150 to 200 RCF, and

- centrifuging for a second period of time at a second RCF, in order to change the relative position of the density gradient medium in the tube (c.f. (131-10) in Fig. 10) by break the gel barrier formed by the separating gel (c.f. (132-10) in Fig. 10) in the tube by accelerating to the range of 100 to 800 RCF, preferably in the range of 300 to 600 RCFg, wherein the second period of time is at least 5 minutes, preferably at least 15 minutes, and most preferably in the range of 15 to 30 minutes.

Fig. 8 illustrates an exemplary embodiment of a third step of the method for automated sample processing according to the invention. In said step, after said continuous two-step centrifugation method, the tube rack head is extracted from the tube rack body by grabbing the tube rack head such that the clippers disengage the tube rack body. This is carried out by means of a robot.

More particularly, as shown in Fig. 8, the tube rack head including tube caps may be extracted from the tube rack body including tubes such that the clippers disengage the tube rack body. Extracting may be performed by means of the robot comprising the illustrated gripper. Various views of this steps are shown in Fig. 8, in which the centrifuge is equipped with a tube rack body, in which tubes are opened (as described and illustrated in Fig. 7, sections A and B) .

Fig. 9 illustrates an exemplary embodiment of a fourth step of the method for automated sample processing according to the invention. In said step, after said extraction of the tube rack head, the tube rack body is extracted from the support of the centrifuge by grabbing the tube rack body. This is again carried out by means of a robot.

More particularly, as shown in Fig. 9, the tube rack body including tubes may be transferred from the centrifuge to a tray. Transferring may be performed by means of the robot comprising the gripper. The tubes in the tube rack body are opened and tube caps are removed (as described and illustrated in Fig. 8) .

Fig. 10 illustrates an exemplary embodiment of the tube at four (A-D) specific stages in the life-cycle of the tube with focus on the state of some key features of the tube filled with a sample throughout automated processing. The tube in Figs. 10 A-D has a label adhered, printed or engraved on the outer surface of the upper section of the tube. In the embodiment shown in Fig. 10, a QR-code (111-10) is adhered to the front-side on the outer surface. Other identification labels such as barcodes and RFID labels can also be used and be adhered on a front-side or a back-side of the tube. It should also be mentioned that, in addition to the label, on the outer surface of the intermediate section, a marker may indicate a preferred volume of sample in the tube. The marker may, for instance, be engraved or dull polished. Such a marker may be helpful as guidance for a practitioner.

Fig. 10 A shows the tube in an off-the-shelf state before venipuncture. In this state the volume of the density gradient medium (131-10) is separated towards a portion above the lowest portion of the tube by a volume of a separating gel (132-10) forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube. An inner surface of the tube above the gel barrier is coated with an atomized anticoagulant. The volume of the tube above the gel barrier and below the tube cap plug is evacuated. The tube cap plug may then be punctured by a needle such that the sample is pulled in the tube by the vacuum into the evacuated tube.

Fig. 10 B shows the tube (200, tube with tube cap inserted) when a sample (whole blood in the present case) was pulled into the tube. The density gradient medium (131-10) remains separated towards the sample above the lowest portion of the tube by the volume of the separating gel (132-10) forming the gel barrier between the density gradient medium and the sample in the tube. In this state the tube is ready for processing with the centrifuge.

Fig. 10 C shows the tube (200, tube with tube cap inserted) including the sample after performing a first centrifugation step within the enhanced continuous two-step centrifugation method (c.f. Figs 6 to 7) . The first centrifugation step includes centrifuging for a first period of time at a first RCF. The first RCF is applied without changing the relative position of the density gradient medium in the tube to achieve an initial cell separation. It can be seen, that the whole blood sample is initially separated. Further processing may allow to achieve an enhanced purity of the samples components, such that the reliability and sensitivity of the subsequent screening methods may be greatly increased. In this state the tube is ready for a second centrifugation step which includes further centrifuging for a second period of time at a second RCF to achieve said enhanced purity of the samples components. Centrifuging is typically not stopped when transitioning from the first centrifugation step to the second centrifugation step.

Fig. 10 D shows the tube (100, without tube cap) including the sample after performing a second centrifugation step within the enhanced continuous two-step centrifugation method (c.f. Figs 6 to 7) . The second centrifugation step includes centrifuging for a second period of time at a second RCF. The second RCF separates the tube cap (210) from the tube (100, tube without tube cap) and releases the density medium (131-10) below the gel barrier (132-10) . It can be seen, that the whole blood sample is further separated as compared the initial separation after the first centrifugation step (c.f. Fig 10 C) . Most importantly, the PBMC layer is clearly visible below the intermediate section with sufficient thickness. In this state the tube may leave the centrifuge for further processing. Qualitative and quantitative analysis may be mentioned as examples which may make use of the enhanced purity of the samples components as achieved after finishing the second centrifugation step.

Fig. 11 shows an assembled closed state (A) as well as an opened state (B, D) of the tube packaging (240-11) including the tube (C, 200, tube with tube cap inserted) . The tube packaging comprises a first (241-11) and a second (242-11) packaging shell. The packaging shells may fit the tube seamlessly. The seamless fit makes sure that there is essentially no space for air in the tube packaging when the tube is placed therein. Hence, disadvantages due to diffusion of liquids or gasses across the body of the tube (e.g. evaporation of the density gradient medium in the tube prior to use) are minimized and the durability of the tube is enhanced. The inner surface of the packaging shells may have an alumina coating (243-11) to protect the tube, e.g. also against UV radiation. An alumina foil may be used as an alumina coating (243-11) , for instance an alumina foil with a thickness of 0.2 mm, which may seamlessly fit into the (inner) shape of the packaging shells (241-11, 242-11) . The edges (244-11) of the packaging shells may be heat sealed after placing the tube in the packaging shells. A score (245-11) at an edge of the packaging shells may provide a means to facilitate the opening of tube packaging. As compared to the absence, the presence of such scores typically greatly enhance the application experience of a user and leads to less damaging. While the exemplary embodiment shown in Fig. 11 shows packaging shells for a single tube, packaging shells for several tubes are also possible, e.g. packaging shells for eight tubes, wherein each tube is placed in its own independent pocket, as shown in Fig. 11. Tubes may also be vacuum sealed and packed in an aluminum packaging to prevent evaporation of the density gradient medium in the tube prior to use. However, a manufacturing procedure for heat sealing is more easily automated than a procedure for vacuum sealing. Hence, even if both vacuum and heat sealing could be used, if it is intended to keep the manufacturing costs low, heat sealing only is preferred.

yFurther, a preferred embodiment of the manufacturing process of the tubes is described:

According to an exemplary embodiment, two injection inlet points are located at the outer edge of the tube’s upper section. This method of injection molding guarantees concentricity from top to bottom of each tube. The thickness of the walls is substantially equal for each tube, e.g. apart from manufacturing tolerances as will be understood by the person skilled in the art. The method may also prevent the problem of eccentric tubes –as is often present when using conventional methods where the injection is usually made from the bottom –that may randomly affect the pressure in the tube when evacuated, which, in turn may affect the volume of the collected sample.

In the following, embodiments of the tube comprising a separating gel including microbeads and embodiments of the method comprising applying a separating gel including microbeads according to the present invention are described in further detail and compared to reference tubes with separating gels devoid of microbeads and corresponding methods.

Fig. 12 A shows a tube 1 according to the present invention, comprising a volume of the density gradient medium (131-10) in the lowest portion of the tube, which is separated towards a portion above the lowest portion of the tube by a volume of a separating gel (132-10) forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube. The density gradient medium (131-10) has a density of 1.077 g/ml, the gel of the separating gel has a density of 1.080 g/ml. This gel becomes thixotropic at a centrifugal force of 1408 g. The separating gel further comprises microbeads with a mesh size of 20-40 (0.4 to 0.841 mm) and a density of 1.8 g/ml. A volume of 100 μl separating gel, including 50 mg microbeads and 50 μl gel component, is applied on top of the density gradient medium. On top of the separating gel, a sample of whole blood 600 is applied.

Fig. 12 B shows the tube 1 (left hand side) after performing a first centrifugation step (a) within the enhanced two-step centrifugation method. The first centrifugation step is performed at 200 g for 15 minutes. As can be seen in Fig. 12 B, the separating gel of the tube 1 remains intact, i.e. the relative position of the density gradient medium in the tube is not changed. It can be seen, that the whole blood sample is initially separated into two phases above the separating gel, an upper plasma phase and a lower phase comprising cells.

Fig. 12 B also shows a reference tube 2 (right hand side) after performing a first centrifugation step (a) . The reference tube 2 comprises a density gradient medium in the lowest portion of the tube, which is separated towards a portion above the lowest portion of the tube by a volume of a separating gel between the density gradient medium and the portion above the lowest portion of the tube. The density gradient medium has a density of 1.077 g/ml, the gel of the separating gel has a density of 1.080 g/ml. However, the separating gel of reference tube 2 does not comprise microbeads. A volume of 100 μl separating gel is applied on top of the density gradient medium. Further, on top of the separating gel, a sample of whole blood 600 is applied, which is initially separated into two phases above the separating gel.

Fig. 12 C shows the tube 1 (left hand side) and the reference tube 2 (right hand side) after performing a second centrifugation step (b) . The second centrifugation step is performed at 400 g for 15 minutes. In case of tube 1, the second centrifugation step breaks the separating gel and releases the density medium (131-10) . While the separating gel usually breaks as soon as a certain centrifugation force is reached, the overall duration of the centrifugation step, such as 15 minutes, is preferred or required to allow sedimentation of the cells in the sample and movement of the density medium. Accordingly, the whole blood sample is further separated and the buffy coat layer 601 is clearly visible. The buffy coat layer is of sufficient thickness for being further processed. In contrast to tube 1, the separating gel of reference tube 2, which is devoid of microbeads, becomes thixotropic only at elevated forces, such as 800 g. Accordingly, a further, third centrifugation step (c) is performed at 800 g for 15 minutes for releasing the density gradient medium. Due to the increased centrifugal force needed for the separating gel to become thixotropic, the buffy coat layer 602 is thinner compared to the buffy coat layer 601 obtained by using tube 1.

Fig. 13 A shows a tube 1 (left hand side) according to the present invention and a reference tube 2 (right hand side) after performing a first centrifugation step (a) .

The tube 1 comprises a volume of the density gradient medium (131-10) in the lowest portion of the tube, which is separated towards a portion above the lowest portion of the tube by a volume of a separating gel (132-10) forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube. The density gradient medium (131-10) has a density of 1.077 g/ml, the gel of the separating gel has a density of 1.080 g/ml. This gel becomes thixotropic at a centrifugal force of 1408 g. The separating gel further comprises microbeads with a mesh size of 20-40 (0.4 to 0.841 mm) and a density of 1.8 g/ml. A volume of 200 μl separating gel, comprising 50 mg microbeads and 150 μl gel component, is applied on top of the density gradient medium.

The reference tube 2 comprises a volume of the density gradient medium as described for tube 1. A separating gel (200 μl, density 1.080 g/ml) is applied on top of the density gradient medium, however, this separating gel does not comprise microbeads.

Both, on top of the separating gel of tube 1 and tube 2, a sample of whole blood is applied and the tubes are centrifuged at 200 g for 15 minutes (step a) .

As can be seen in Fig. 13 A, the whole blood sample is initially separated into two phases above the separating gel of tube 1 and tube 2, an upper plasma phase and a lower phase comprising cells, i.e. the separating gel of both tube 1 and tube 2 do not break at this first centrifugation step.

Fig. 13 B shows the tube 1 and the tube 2 after performing a second centrifugation step (b) . The second centrifugation step is performed at 400 g for 15 minutes. In case of tube 1, the second centrifugation step breaks the separating gel and releases the density medium (131-10) . As explained above, as soon as a certain centrifugal force is reached, the separating gel breaks, while the overall centrifugation duration allows separation o the cells in the density medium. Accordingly, the whole blood sample is further separated and the buffy coat layer 601 is clearly visible. In contrast to tube 1, the separating gel of reference tube 2, which is devoid of microbeads, becomes thixotropic only at elevated forces. Accordingly, a further centrifugation step (c) at 1700 g for 15 minutes is required for releasing the density gradient medium. Due to the increased centrifugal force needed to stimulate the separating gel to become thixotropic, the buffy coat layer 602 is thinner compared to the PBMC layer 601 obtained by using tube 1, and, hence, more difficult to process.

It can be deduced from the experiments described with reference to Fig. 12 and Fig. 13 that the presence of microbeads in the separating gel allows for a constant, low centrifugal force, even if the volume of the separating gel is increased. To the contrary, separating gels devoid of microbeads require higher centrifugal forces with larger volumes, ultimately leading to a decrease in the overall targeted cell recovery rate.

Fig. 14 A shows a tube 1 (left hand side) according to the present invention after performing a first centrifugation step (a) within the enhanced two-step centrifugation method (left hand side) and after performing a second centrifugation step (b) within the enhanced two-step centrifugation method (right hand side) . In this case, tube 1, comprising a density gradient medium and a separating gel, has been prepared approximately 11 weeks before use, i.e. before application of a sample (whole blood) and centrifugation. The tube is prepared to comprise a density gradient medium and a separation gel with microbeads as described above with reference to Fig. 12, comprising 100 μl of separating gel (50 mg microbeads and 50 μl gel component) .

After centrifugation step (a) at 200 g for 15 minutes, the separating gel remains intact, allowing an initial plasma-cell separation of the sample. By performing a centrifugation step (b) at 400 (and also at 600 g) , e.g. for 15 minutes, the separating gel initially breaks and the cells separate, such that the buffy coat layer 601 is clearly visible and extractable.

The platelet recovery rate is calculated by platelet counting of the buffy coat layer 601 obtained from three independent samples, as described with reference to Fig. 14 A, with the Sysmex XS-500i. The obtained recovery rates are: 94.93 %, 94.84 %and 90.00 % (mean: 93.26 %) .

Fig. 14 B shows a reference tube 2 after performing a first centrifugation step (a) (left hand side) and after performing a second centrifugation step (b) (right hand side) . Reference tube 2 has been prepared approximately 11 weeks before use, i.e. before application of a sample (whole blood) and centrifugation. The tube is prepared to comprise a density gradient medium and a separation gel without microbeads as described above with reference to Fig. 12, tube 2 with 100 μl separating gel (i.e. 100 μl gel component) . After centrifugation step (a) at 200 g for 15 minutes, the separating gel remains intact, allowing an initial plasma-cell separation of the sample. However, centrifugation step (b) needs to be performed at higher centrifugal forces of about 1500 to 1700 g in order to stimulate the separating gel to become thixotropic. Accordingly, the buffy coat layer 602 is thinner compared to the layer 601 obtained from tube 1.

The platelet recovery rate is calculated, as described above, with the Sysmex XS-500i, based on three independent samples of the buffy coat layer 602. The obtained recovery rates are: 68.04 %, 85.10 %and 66.03 % (mean: 73.06 %) .

The above recovery rates obtained with tube 1 according to the present invention in comparison to reference tube 2 demonstrate that by using a separating gel with microbeads and by applying lower centrifugal forces, the overall platelet recovery from the buffy coat layer can be significantly increased.

Reference numerals

1 tube comprising density gradient medium and separating gel with

microbeads

2 reference tube comprising density gradient medium and separating gel

without microbeads

100 tube (without tube cap)

110 upper section

111-10 label (e.g. QR code)

120 intermediate section

130 lower section

131-10 density gradient medium

132-10 separating gel

140 fastening means (tube rib)

150 spherical ending

200 tube (with tube cap inserted)

210 tube cap

220 tube cap body

221-4 circumferentially protrusion

230 tube cap plug

231-4 upper cylindrical bar

232-4 lower cylindrical bar

240-11 tube packaging

241-11 first packaging shell

242-11 second packaging shell

243-11 alumina coating

244-11 edges (of the packaging shells)

245-11 score (of the packaging shells)

300 tube rack (with tubes and tube caps inserted)

310 tube rack (without tubes and tube caps inserted)

320 tube rack body

330 tube holder

331 opening

332-4 wall

333-4 protruding ring

334-4 symmetrical trajectory

340 tube rack head

341 clipper

342-4 groove

343-4 crown-shaped upper part

344-4 inwardly extending bump

400 tube rack (cross-section, with tubes and tube caps inserted)

520 tray

530 centrifuge

540 support

600 whole blood sample

601 buffy coat layer

602 buffy coat layer (reference example)

Claims

A tube for sample collection and sample processing, comprising a volume of a density gradient medium in a lowest portion of the tube,

wherein the volume of the density gradient medium is separated towards a portion above the lowest portion of the tube by a volume of a separating gel forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube,

wherein the separating gel comprises microbeads.
The tube according to claim 1, wherein the microbeads have a density equal to or above 1.5 g/ml.
The tube according to any one of the preceding claims, wherein the microbeads have a density in the range of 1.8 to 2.5 g/ml.
The tube according to any one of the preceding claims, wherein the microbeads are of an essentially round shape, preferably with a diameter in the range of 0.4 to 1 mm.
The tube according to any one of the preceding claims, wherein the microbeads are comprised in the separating gel in a concentration of about 10 to 50 %weight per weight or weight per volume.
The tube according to any one of the preceding claims, wherein the density gradient medium has a density between 1.01 and 1.119 g/ml, preferably between 1.077 g/ml and 1.083 g/ml.
The tube according to any one of the preceding claims, wherein the volume of the density gradient medium is between 100 and 600 μl, preferably between 200 and 400 μl, and

the volume of the separating gel is between 35 and 300 μl, preferably between 100 and 200 μl.
The tube according to any one of the preceding claims, wherein the tube is manufactured by plastics injection molding.
The tube according to any one of the preceding claims, wherein the tube is made of glass.
The tube according to any one of the preceding claims, comprising:

an upper section, an intermediate section, and a lower section, wherein

the upper section and the lower section are substantially of cylindrical shape, the upper section has an inner diameter larger than an inner diameter of the lower section,

the upper section has an outer diameter larger than an outer diameter of the lower section,

the intermediate section is located between the upper section of the tube and the lower section, wherein

a top of the intermediate section connects to a bottom of the upper section and a bottom of the intermediate section connects to a top of the lower section, and

the intermediate section, wherein

an inner diameter and an outer diameter of the intermediate section decreases from the top to the bottom of the intermediate section of the tube;

a plurality of fastening means for fixing the tube in a tube rack, wherein

the plurality of fastening means is located on an outer surface of the intermediate section and the lower section.
The tube according to claim 10, wherein the intermediate section is of a tapered shape.
The tube according to any of claims 10 or 11, wherein

the plurality of fastening means comprises a plurality of longitudinally extending tube ribs for fixing the tube in the tube rack.
The tube according to any of claims 10 to 12, wherein

the outer diameter at the top of the intermediate section is substantially equal to the outer diameter of the upper section, and

the inner diameter at the top of the intermediate section is substantially equal to the inner diameter of the upper section.
The tube according to any of claims 10 or 13, wherein

the inner diameter at the bottom of the intermediate section is substantially equal to the inner diameter of the lower section, and

the outer diameter at the bottom of the intermediate section is substantially equal to the outer diameter of the lower section.
The tube according to any of claims 10 to 14, wherein

the plurality of tube ribs is spaced apart at equal distances.
The tube according to claim 15, wherein

the plurality of tube ribs are two tube ribs that are 180° apart from each other.
The tube according to any of claims 10 to 16, wherein

the plurality of tube ribs substantially extends along the whole length of the intermediate and the lower section.
The tube according to any of claims 10 to 17, wherein

the outer diameter of the upper section is substantially equal to a distance ranging from an outer edge of a first tube rib of the plurality of tube ribs to an outer edge of a second tube rib of the plurality of tube ribs.
The tube according to any of claims 10 to 18, wherein

the inner diameter at the top of the intermediate section of the tube is 10.5 mm, and/or

the inner diameter at the bottom of the intermediate section of the tube is 6.5 mm, and/or

a thickness of the tube ribs is 2.0 mm.
The tube according to any of claims 10 to 19, further comprising

a tube cap, wherein

the tube cap is insertable into the upper section such that the tube cap seals the tube, and

the tube cap is configured to be held against a force in an axial direction towards the lower end of the lower section of the tube such that the tube is pulled off the tube cap by said force.
The tube according to claim 20, wherein the tube cap further comprises a tube cap body and a tube cap plug, wherein

the tube cap plug is insertable into the upper section such that the tube cap plug seals the tube, and

the tube cap body is configured to be arranged around the upper section and to engage the tube cap plug, and is further configured to be held against a force in an axial direction towards the lower end of the lower section of the tube such that the tube is pulled off the tube cap by said force.
The tube according to any one of claims 20 to 21, wherein

the tube cap is pierceable by a needle such that an evacuated tube with the tube cap inserted into the upper section receives a sample through the needle pierced into the tube cap.
The tube according to any one of claims 21 to 22, wherein

the tube cap body has substantially the shape of a cylindrical tube, wherein

an inner diameter of a lower portion of the tube cap body is substantially equal to the outer diameter of the upper section, and

an inner diameter of an upper portion of the tube cap body is substantially equal to the diameter of the upper cylindrical bar of the tube cap plug.
The tube according to any one of claims 21 to 23, wherein the tube cap body comprises

at least two circumferentially protrusions to engage the tube cap and

the tube cap plug.
A method for separating a volume of a density gradient medium comprised in a lowest portion of a tube, the method comprising the step of adding a volume of a separating gel forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube, wherein the separating gel comprises microbeads.
The method of claim 25, wherein the separating gel is a separating gel as defined in any one of claims 2 to 5, and/or wherein the density gradient medium is as defined in claim 6.
Use of a separating gel comprising microbeads for separating a volume of a density gradient medium comprised in a lowest portion of a tube by forming a gel barrier between the density gradient medium and the portion above the lowest portion of the tube.
Use according to claim 27, wherein the separating gel is a separating gel as defined in any one of claims 2 to 5, and/or wherein the density gradient medium is as defined in claim 6.
A continuous two-step centrifugation method for enhanced sample enrichment in a tube according to any of claims 1 to 24, the method comprising the steps of:

centrifuging for a first period of time at a first relative centrifugation force (RCF)

without changing relative position of the density gradient medium in the tube to achieve an initial cell separation, wherein

the first period of time is at least 10 minutes, preferably in the range of 10 to 20 minutes, and the first RCF is in the range of 50 to 300 RCF, and

centrifuging for a second period of time at a second RCF, in order to

change the relative position of the density gradient medium in the tube by accelerating to the range of 100 to 800 RCF, preferably 300 to 600 RCF, wherein

the second period of time is at least 5 minutes, preferably in the range of 15 to 30 minutes.
The continuous two-step centrifugation method according to claim 29, wherein centrifuging for the second period of time is performed by accelerating to a centrifugation force which does not exceed 600 RCF.