WO2010133997A1

WO2010133997A1 - Diagnostic device with sample application detector

Info

Publication number: WO2010133997A1
Application number: PCT/IB2010/052015
Authority: WO
Inventors: Albert H. J. Immink; Jeroen H. Nieuwenhuis; Joost H. Maas
Original assignee: Koninklijke Philips Electronics N. V.
Priority date: 2009-05-20
Filing date: 2010-05-07
Publication date: 2010-11-25

Abstract

The present invention relates to cartridges (1) for diagnostic devices comprising a sample fluid application region (2), a reaction chamber (4) and a channel (3) connecting the application region to the reaction chamber. The device further comprises sensors (5, 6, 7) to detect the application of a sample and to detect the filling of the reaction chamber.

Description

DIAGNOSTIC DEVICE WITH SAMPLE APPLICATION DETECTOR

FIELD OF THE INVENTION

The present invention relates to cartridges for diagnostic devices with sensors to detect the presence of a sample liquid. The present invention further relates to methods to perform diagnostic assays wherein the presence of a sample liquid at different portions in a cartridge is measured and decisions are made to continue or discontinue an assay.

BACKGROUND OF THE INVENTION

Diagnostic devices for drug of abuse testing in saliva or for medical diagnostics in blood samples are more and more used in point-of-care situations where the test is performed directly at the roadside, the bedside, at the physician's office or even at home. For samples such as blood, it is important that the required sample volume is as low as possible, especially when this has to be done frequently (e.g. up to a few times per day). Generally, the simplest way to obtain blood is by a finger-prick. Typically, 20 μl can be conveniently withdrawn from the finger. For this reason, cartridges are being developed that have a dead volume that is as low as possible. Such a cartridge typically fills automatically without any further operator intervention, by capillary filling of a channel between the application region and the reaction chamber and the reaction chamber itself, after the blood has been applied to the application zone of a cartridge.

The operator of a device can not easily assess by visual observation if the volume of applied sample was large enough to fill the complete cartridge. Performing an assay and relying on the assay results when the reaction chamber is not or incompletely filled may have legal (especially in drug of abuse testing) or medical consequences.

In US 5,352,351 'wetting sensors' are described which detect the entrance and/or filling of a sample liquid in a reaction chamber. However, there are no adequate methods to detect and evaluate the proper application of a sample in a cartridge. When a sample does not reach the reaction chamber, or does not completely fill the chamber, the system will not detect wetting and the assay procedure will not start. After applying the sample the operator, will be kept waiting without getting an assay result. SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved device with regard to the aforementioned problem. The invention is defined by the independent claims. The dependent claims provide advantageous embodiments. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

One aspect of the invention relates to a cartridge (1) for a diagnostic device (11) comprising a sample fluid application region (2), a reaction chamber (4) and a channel (3) connecting the application chamber to the reaction chamber. The channel (3) comprises a proximal (31) and a distal part (32). The reaction chamber comprises a sensing zone (5) at the exit of the reaction chamber for detection the filling of the reaction chamber with sample fluid. In this cartridge, the sample application region (2) or the proximal part of the channel (31) comprises a sensing zone (7) for sensing the application of the sample fluid on the cartridge.

Optionally, such cartridges comprise a sensing zone (6) for sensing the sample fluid at the entry of the reaction chamber.

According to embodiments of cartridges describes herein the sensing zone is an electrode or a transparent region for optical detection.

According to embodiments of cartridges describes herein, the sample application zone comprises a filter (8) for retaining cells from a blood sample. Optionally, the sensing zone (6) is in contact with the filter (8).

Another aspect of the invention relates to a device (11) for performing a diagnostic assay, comprising a cartridge as described above, wherein the device comprising detection units (51) and (71) and optionally detection units (61) for detecting the presence of a liquid on the sensing zones.

According to embodiments of device describes herein, these devices further comprise a data processing unit (10) for measuring the time between the application of the sample fluid and the filling of the device.

Such a detection unit can be photospectrometer.

In particular embodiments, the detection unit measures frustrated total internal reflection (FTIR) or measures changes in conductivity. According to embodiments of device describes herein, further comprising control elements (91) are present which interact with a data processing unit (10) for starting or stopping an assay.

Another aspect of the present invention relates to a method for performing an assay in a cartridge according to claim 1, inserted in a diagnostic device (11). This method comprising the steps of:

(a) applying a sample to the sample application region (2) ,

(b) recording the contact of sample fluid on the sensing zone (6) at the application region (2) or at the proximal part (31) of the channel (3) connecting the sample application region (2) with the reaction chamber (4),

(c) optionally, recording the presence of the sample liquid on the sensing zone (7) at the inlet of the reaction chamber,

(d) recording the presence of the liquid at the sensing zone (5) at the exit of the reaction chamber. At this point a choice is made depending on whether or not, the reaction chamber is filled within a predetermined time period.

When a predefined time period between the recording at step (b) and the recording at step (d) is not exceeded, the assay starts in the reaction chamber (4),

When the time elapsed the recording at step (b) and the recording at step (d) exceeds a predetermined time, a signal is displayed for applying a further sample, or alternatively the assay is aborted.

Another aspect of the invention related to a device (11) for performing a diagnostic assay comprising a cartridge. Herein, the cartridge comprises a sample fluid application region (2), a reaction chamber (4) and a channel (3) connecting the application chamber to the reaction chamber, the cartridge comprising one or sensing zones for detecting the presence of sample fluid within the cartridge. The device comprises a detection unit for detecting the presence of a liquid on the one or more sensing zones, and the device comprises a sensor for detection the presence of the cartridge in the device.

A further aspect of the present invention relates to a method for quality control of a diagnostic assay. The method comprising the steps of:

- providing a cartridge (1) for a diagnostic device (11), the cartridge comprising a sample fluid application region (2), a reaction chamber (4) and a channel (3) connecting the application chamber to the reaction chamber, the cartridge comprising one or more sensing zones (5, 6, 7) for detecting the presence of sample fluid within the cartridge, - inserting the cartridge into the device,

- detecting the insertion of the cartridge with a sensor (12) located in the device, -applying a sample to the cartridge in the device.

-determining the time elapsed between the insertion of the cartridge into the device and the detection of sample liquid on a sensing zone,

- comparing the time elapsed with a predetermined, and

- aborting the assay if the elapsed time exceeds the predetermined time. whether or not sample liquid is detected on the one or more sensing zones, and if the sample liquid is not detected with the predetermined time period, aborting the assay. In particular embodiments, the sensing zone is positioned at the exit of the reaction chamber.

The sensing zones and their arrangement as described in the present invention allow problems with sample application, sample transport, and filling of a reaction chamber to be identified. When the sample volume is not enough to reach the sample chamber the system will not detect wetting and the assay/actuation procedure will not start. A similar problem occurs when the cartridge is damaged, the sample is too viscous, or contains particulate matter that blocks or retards the fluid flow. In such conditions the operator (and more important the patient) will keep waiting but will not get an assay result. The design and use of cartridges make it possible to perform an assay without running an external timer, or to push a button after sample application, because the moment of sample application is known to the system. This makes the described methods very convenient and less prone to errors.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1 shows a schematic overview of a cartridge (1) inserted into a diagnostic device (11) in accordance with an embodiment of the invention. Fig. 2 shows examples of configurations of sample application zones (2) with sensing zone (7).

Fig. 3 shows a schematic overview of a cartridge (1) inserted into a diagnostic device (11) in accordance with an embodiment of the invention, wherein the device further comprises a sensor (12) for detecting the insertion of the cartridge into the device. In the different Figs., the same reference signs refer to the same or analogous elements.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The following terms or definitions are provided solely to aid in the understanding of the invention. These definitions should not be construed to have a scope less than understood by a person of ordinary skill in the art.

Definitions

"Sensor" as used herein relates to a means for detecting the presence of an aqueous liquid. A sensor comprises a sensing zone in a cartridge, which is connected to a detection unit in a diagnostic device upon insertion of the cartridge in the device.

"proximal" as used herein describes the part of a structural element (channel, reaction chamber) adjacent to the sample inlet.

"distal" as used herein describes the part of a structural element (channel, reaction chamber) adjacent to the entrance to the reaction chamber and remote from the sample so that the distal part is located further down the sample stream direction from the sample inlet than the proximal part.

Cartridges as described herein are housings comprising a sample application region which is separated from a reaction chamber by a channel. Fig. 1 shows a schematic overview of a cartridge (1) inserted into a diagnostic device (11) in accordance with an embodiment of the invention, wherein the cartridge comprises a sample application region (2), connected via a channel (3), with a proximal (31) and distal side (32), to reaction chamber (4). The cartridge contains sensing zones (5, 6 and 7) connected via a detection unit (51, 61, and 71) to a data processing unit (10). A filter (8) is depicted within the sample application region. Means for performing an assay (9) and control elements (91) for performing, detecting and processing assay results are indicated.

This configuration allows inserting a cartridge in a device such that the sample application region, which may have been contaminated by contact with fingers or mouth, remains outside the device when this is inserted in the device. In this configuration the cartridge will become already (partially) filled with sample liquid before the insertion into the device. Upon insertion the presence of sample liquid at one or more of the sensing zones will be monitored.

The configuration also encompasses inserting the appropriate cartridge in a device, where after a sample is applied on the sample application region of the cartridge.

Methods and cartridges as describes in embodiments of the present invention are particularly suitable when a cartridge is inserted in a device prior to the application of a sample on the inserted cartridge.

The sample application region, which is connected to the channel, may differ in size, shape and material depending on the type of sample or the design of the cartridge. Typically a sample application region is a depression in the cartridge defining a small volume. Alternative sample application regions are made of fabrics (paper, cellulose, etc.) which stick out of a cartridge and which provide a wick connecting the exterior of the cartridge to the channel. Alternatively the sample application region can have the form of an internal space within the cartridge which is filled by a syringe or a sponge, where after the sample liquid further migrates from this space to the channel.

In certain embodiments, the sample application region comprises a filter element for removing particulate matter from a sample (e.g. cells and organelles in a blood sample, or food particles or epithelial cells in a saliva sample In particular embodiments, a wick as described above serves both as a sample application region and as filter.

The length of the channel connecting the sample application region and the reaction chamber is determined by the design of the cartridge and is typically limited such that the volume of the channel is between 0.1 and 2 μl. The diameter of the channel is typically between 50 μm and 500 μm and depends from factors such as the amount of sample fluid available, the viscosity of the sample fluid or the presence of particulate matter in the sample fluid. Note that the channel may have different width and height. The channel may optionally comprise reagents and buffering compounds.

A channel may, according to a particular embodiment, have bifurcations to distribute a sample to a plurality of reaction chambers, e.g. for the independent detection of different blood markers or different drugs of abuse.

The reaction chamber is the part of the cartridge wherein the reaction of an analyte or analyte analogue is performed, such as an enzymatic assay or a binding assay of an analyte with a probe. Frequently used probes are antibodies or oligonucleotides. The cartridges of the present invention are typically used for performing sandwich immunoassays (e.g. cardiovascular markers in blood) or competitive immunoassays (drugs of abuse in sputum).

Typically the detection of the analyte reaction equally takes place within the reaction chamber, accordingly functioning also as a detection chamber. Although this is not a prerequisite for the cartridges and methods of the present invention, the combined reaction and detection in the same chamber, reduces the size of a sample that is needed. For the detection of a binding assay probes or analyte analogues are bound to a detectable label. In particular embodiments the detectable label is a magnetic particle.

The sample application region (and the filter if present), the channel and the reaction chamber define the size of the sample volume required to fill the cartridge such that the reaction chamber is completely filled with sample fluid. Typically, this volume ranges from about 10 μl to about 100 μl.

In order to monitor the filling of the cartridge, different sensing zones are present in the cartridge. A first sensing zone (7) is located in the sample application region or adjacent to the sample application region (i.e. in the proximal region (31) of the channel), such that upon, or immediately after the application of a liquid, its presence is recorded. This sensing zone, when positioned in the sample application region, can be positioned e.g. at the wall or the bottom of a depression, or can be positioned before or after a filter if such an element is present. A non-limiting list of examples is depicted in Fig. 2. Alternatively the sensing zone (7) is located at the proximal part (31) of the channel (3). In the context of the embodiments described herein, this refers to a position in the channel such that after application of 10, 5 or even 1 % of the required sample volume for an assay, liquid is recorded by the sensing zone in this proximal part of the channel. Required sample volume refers to the volume needed to fill the channel and the reaction chamber, optionally further including the volume that remains in the sample application region (e.g. liquid attached to the walls or needed to wet a filter if present). By its position the sensing zone (7), accordingly records the application of a sample in a device.

In a particular embodiment, a plurality of sensing zones can be provided in the channel to monitor and indicate the flow of the sample into the channel.

A further sensing zone (6), which is optionally present in the cartridge, is located at the entrance of the reaction chamber or in the distal part (32) of the channel. This zone records the entry of the sample in the reaction chamber. This event can be used to start within the device functions such as mixing of reagents and probes, in order to condition the sample for the subsequent assay.

A further sensing zone (5) is located at the exit of the reaction chamber, in the distal part of the reaction chamber, at the exit of the reaction chamber or optionally in a channel downstream of the reaction chamber. This sensing zone records the complete filling of the reaction chamber. This event can be used to start one or more functions within the device, including mixing, binding of probe and reagent, washing steps, and detection steps.

The detection of a liquid at a sensing zone can be performed in different ways. According to one embodiment a sensor measures a change in an electric property, such a change in conductivity or in impedance upon the presence of an aqueous liquid between two electrodes. Alternatively, a change in capacitance is measured. According to another embodiment the detection with a sensor is based on an optical detection (surface or bulk effect) and measures for example a change in surface reflection (e.g. Frustrated Total Internal Reflection), diffraction, refraction, absorbance or a change in absorbance maximum. Detection can take place in the visible part of the spectrum or at the infrared or UV region. The cartridges and methods of the present invention are suitable for colourless

(e.g. saliva) as well as coloured (e.g. blood or urine) sample fluids. They are equally suitable for non- viscous samples such as urine or for more viscous fluids (saliva) or fluids containing particulate matter such as blood or saliva).

In particular embodiments, devices for assaying blood can be equally used for other liquids which are essentially colourless, such as sputum, by applying a detectable agent (visible dye, fluorophore, phosphorophore) at the sample application zone or in a filter such that the dye dissolves upon contact with the sample liquid and generates a coloured liquid. Accordingly, another aspect of the present invention relates to a method for performing an assay in the above-described cartridge upon insertion in a diagnostic device. Generally, a sample is applied to the sample application region (2) and the contact of the sample fluid on the sensing zone (6) at the application region or at the proximal part 31 of the channel (3) connecting the sample application region to the reaction chamber, is recorded. The user of the device can be notified of the proper application of the sample fluid by a message on a display, a light signal or a sound signal when the sample fluid contacts the sensing zone. The absence of such as signal with a predetermined time as indicated in the instructions of the device, warns the user of a deficiency in the sample application. Alternatively, the device gives a warning to the user when the signal is absent for a predetermined time after detected application of the sample to the cartridge. Depending on the design of the device and its operation, the signal can be used for two alternatives instructions. In a first setting the warning sign automatically results in an abortion of the assay. In a second setting, the warning signs allows the user to apply within a predetermined time period a further amount of sample, whereafter the assay can continue. If however, the further amount of sample is not applied within this predetermined time period, the assay will be aborted.

The time between the application of a sample (e.g. applying a pricked finger) and such signal, depends on factors such as the time needed to permeate through a filter, the viscosity of the sample and the position of the sensing zones.

Optionally, the presence of the sample liquid on the sensing zone (7) at the inlet of the reaction chamber is recorded. This indicates that the sample has properly migrated from the application region into the channel. By measuring the time difference between wetting of two wetting sensors at a known geometrical distance along the channel it is possible to calculate the fluid speed in a straightforward way. Alternatively, additional sensing zones can be provided along channel (3) to calculate the flow speed in such tubular element. A lower speed can be indicative of obstruction in the cartridge, excessive particulate matter in the sample, or a too high viscosity of a sample fluid. A signal can be given that the sample successfully reached sensing zone (6), or a warning sign can be given if the time lapsed between the contact of the liquid with sensing zone (6) and (7) is above a predetermined time period. The filling of the reaction chamber is recorded by the presence of liquid at the sensing zone (5) at the exit of the reaction chamber. When a predefined time period between recording the application of the sample on the sensing zone (6) and/or (7) and the filling of the reaction chamber is not exceeded, the assay in the reaction chamber is started (i.e. the sample liquid is sensed at zone (7) and (5) and the period between detection at zone (7) and zone (5) does not exceed a predetermined time). The timely filling of the reaction chamber can be notified to the user with a signal. Alternatively, if the time period between the application of the sample and the filling of the reaction chamber exceeds a predetermined time period (i.e. if no detection at zone (5) takes place within a predetermined time after detection at zone (7)), a warning signal can be given, requesting supplementary sample liquid, or the further operation of the assay can be stopped.

The above outlined method allows the detection of sample application to a cartridge. At that moment a timer can start running in the device. The wetting sensors at the exit of the reaction chamber should then detect the sample fluid within a predefined time. If that is not the case the analyser can go in a out-of-control handling mode. At this point two events are possible:

The measurement is aborted and an error message is shown on a graphical display, by a light signal or a sound. A new test is only possible by removing the cartridge and inserting a new one. lternatively, a warning is given to the reader with a request to apply a second drop of sample to the cartridge. Again the time between the request for a second drop and the actual detection of liquid in the reaction chamber can be subject to a predetermined time-out interval (e.g. in order to avoid sample degradation when the application of the second drop takes too long). In order to perform the methods of the present invention, the device is provided with a data processing unit (10) which records and calculates the time between the wetting of the different sensing zone. This data processing unit interacts with the control elements (91) of the device to decide on starting, continuing or aborting an assay, depending upon the moment at which the liquid is detected by the different sensing zones.

The presence and use of the different sensors allows different alternative quality controls to be performed on an assay. The presence of sensing zone 6 and 7 allow to automatically ready the device for an assay procedure, more particularly to start reagent mixing (by e.g. magnetic actuation) as soon as wetting of both sensing zones 6 and 7 is detected. Starting of the actuation procedure can also be started after a predetermined time after the wetting of sensing zone 6 or 5, in order to allow the dry beads and reagents to dissolve in the sample fluid. An automatic and predefined start of the actuation procedure can be of importance to get a reliable result with low assay-to-assay variability, especially for assays where binding kinetics indicate that the biological reaction is, or may not, be at equilibrium during the assay. Other arrangements of the systems and methods embodying the invention will be obvious for those skilled in the art.

It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention.

Cartridges equipped with a sensing zone for detecting the presence of a sample liquid can also be used to ensure the proper use of cartridges comprising biological materials and reagents which may be prone to light, humidity and heath. Typically, cartridges are stored prior to their use in a packaging in a environment with a controlled temperature and atmosphere. Upon application of a cartridge in a device, reagents in the cartridge may become subject to humidity, moisture, oxidising conditions and heat, and the assay should be completed within a certain time period to assure that the reagents do not decompose. Accordingly, a further aspect of the invention relates to device comprising a sensor for the insertion of a cartridge, a cartridge comprising a sensing zone for the detection of a sample liquid and a clock measuring the time between the insertion of the cartridge in the device and the application of the sample. If a too long time period is recorded between the two above events, a warning signal is given to the user and/or the assay is stopped. For this application any of the sensing zones as described in the cartridges of the present invention can be used. In particular the sensing zone detection the filling of the reaction chamber is suitable for this purpose.

The insertion of the cartridge can be recorded by any means known in the art, for example by a mechanical switch in the device which is activated upon physical contact with the cartridge, or by the presence of a strip of conductive material on the cartridge which fits with an interrupted electrical circuit in the device.

Claims

CLAIMS:

1. A cartridge (1) for a diagnostic device (11) comprising a sample fluid application region (2), a reaction chamber (4) and a channel (3) connecting the application chamber to the reaction chamber, the channel comprising a proximal part (31) adjacent to the sample inlet and a distal part (32) adjacent to the entrance to the reaction chamber and remote from the sample inlet, said reaction chamber comprising a sensing zone (5) at the exit of said reaction chamber for detection the filling of the reaction chamber with sample fluid, characterised in that said sample application region (2) or said the proximal part of said channel (31) comprises a sensing zone (7) for sensing the application of said sample fluid on the cartridge.

2. The cartridge according to claim 1, further comprising a sensing zone (6) for sensing said sample fluid at the entry of said reaction chamber.

3. The cartridge according to claim 1 or 2, wherein the sensing zone is an electrode.

4. The cartridge according to claim 1 or 2, wherein the sensing zone is a transparent region for optical detection.

5. The cartridge according to any of claims 1 to 4, wherein the sample application zone comprises a filter (8) for retaining cells from a blood sample.

6. The cartridge according to claim 5, wherein the sensing zone (6) is in contact with said filter (8).

7. A device (11) for performing a diagnostic assay, comprising a cartridge according to any of claims 1 to 6, said device comprising detection units (51) and (71) and optionally detection units (61) for detecting the presence of a liquid on said sensing zones.

8. The device according to claim 7, further comprising a data processing unit (10) for measuring the time between the application of said sample fluid and the filling of said device.

9. The device according to claim 7 or 8, wherein the detection unit is a photospectrometer.

10. The device according to 7 or 8, wherein the detection unit measures frustrated total internal reflection (FTIR) .

11. The device according to claim 7 or 8, wherein the detection unit measures changes in conductivity.

12. The device according to claim any of claims 1 to 11 further comprising control elements (91) interacting with data processing unit (10) for starting or stopping an assay.

13. A method for performing an assay in a cartridge according to claim 1, inserted in a diagnostic device (11), comprising the steps of: (a) applying a sample to the sample application region (2) ,

(b) recording the contact of sample fluid on the sensing zone (6) at the application region (2) or at the proximal part (31) of the channel (3) connecting the sample application region (2) to the reaction chamber (4),

(d) recording the presence of the liquid at the sensing zone (5) at the exit of the reaction chamber

(el) when the period between the recording at step (b) and the recording at step (d) does not exceed a predetermined time, starting the assay in the reaction chamber (4), or (e2) when a predefined time period between the recording at step (b) and the recording at step (d) is exceeded, displaying a signal for applying a further sample or aborting the assay.

14. A device (11) for performing a diagnostic assay, comprising a cartridge, wherein the cartridge comprises a sample fluid application region (2), a reaction chamber (4) and a channel (3) connecting the application chamber to the reaction chamber, said cartridge comprising one or sensing zones for detecting the presence of sample fluid within the cartridge wherein the device comprises a detection unit for detecting the presence of a liquid on said one or more sensing zones, and wherein the device comprises a sensor for detection the presence of the cartridge in the device.

15. A method for quality control of a diagnostic assay, said method comprising the steps of:

- providing a cartridge (1) for a diagnostic device (11), said cartridge comprising a sample fluid application region (2), a reaction chamber (4) and a channel (3) connecting the application chamber to the reaction chamber, said cartridge comprising one or more sensing zones (5, 6, 7) for detecting the presence of sample fluid within the cartridge,

- inserting the cartridge into the device,

- detecting the insertion of the cartridge with a sensor (12) located in the device,

- applying a sample to the cartridge in the device. - determining the time elapsed between the insertion of the cartridge into the device and the detection of sample liquid on a sensing zone,

- comparing the time elapsed with a predetermined, and

- aborting the assay if the elapsed time exceeds the predetermined time.

16. The device according to claim 15 or the method according to claim 15, wherein the sensing zone is positioned at the exit of the reaction chamber.