Porous membrane sensor assembly

Abstract

The present invention relates to a sensor assembly for analyzing complex fluid samples. The sensor assembly includes a sample chamber for accommodating complex fluid samples, the sample chamber being defined by a chamber wall and having an inlet and an outlet, the inlet and the outlet defining a flow direction from the inlet toward the outlet for fluid processing in the sample chamber. The sample chamber includes a first sample space and a second sample space. The second sample space includes a porous membrane sensor element for detecting an analyte in a continuous portion of the complex fluid sample. The porous membrane sensor element includes a porous membrane having a front side defining a sensor surface for contacting the fluid sample, the sensor surface facing the second sample space, and the porous membrane including pores extending from corresponding openings at the sensor surface into the porous membrane. The pores are configured with respect to the analyte for communicating with a diffusion fluid of the second sample space. The sample chamber further includes a flow disturbance element, which is arranged upstream of the second sample space and between the first sample space and the second sample space.

Description

Technical Field

[0001] The present invention relates in one aspect to a sensor assembly for analyzing a complex fluid sample with respect to one or more analytes, the sensor assembly comprising a sample chamber for accommodating the complex fluid sample. According to another aspect, the present invention relates to a sensor assembly for detecting high molecular weight components in a continuous portion of a complex fluid sample present in the sample chamber. According to another aspect, the present invention relates to a sensor assembly comprising a porous membrane sensor arranged in the sample chamber. According to another aspect, the present invention relates to a sensor assembly for detecting high molecular weight components in a continuous portion of a complex fluid sample present in a sample chamber comprising a porous membrane sensor. According to another aspect, the present invention relates to a sensor assembly for detecting high molecular weight components in a continuous portion of a complex fluid sample present in a sample chamber comprising a porous membrane sensor, and for detecting further analytes of the same complex fluid sample by means of further sensors arranged in the sample chamber. According to yet another aspect, at least the high molecular weight components are detected by optical detection. Background Art

[0002] The detection of analytes in complex fluids containing both continuous and discontinuous parts is a challenging but frequently encountered measurement problem. Typically, the measurement comprises a sample preparation step, including separation, for example, by filtration, sedimentation and / or centrifugation, and a subsequent detection measurement step, using a chemical indicator reaction and / or a physical interaction that is sensitive to the analyte in question. In this case, a complex challenge is often to prepare and present a suitable sample for detection without affecting the measurement, especially if the volume of available sample is small and if the fluid to be analyzed is very complex. In addition to this, in this case, multiple parameters often have to be determined for the same sample, which imposes additional constraints on combining a given measurement for the detection of the analyte with measurements of other parameters.

[0003] Therefore, there is a need for a highly sensitive, simple and rapid technique that allows for the selective detection of analytes in complex fluids, which technique is also suitable for easy integration with other measurement techniques for determining multiple parameters of the same sample. There is also a need for a desirable technique that provides gentle separation, extraction and / or isolation of the analyte for detection measurements, i.e., without damaging the rest of the fluid to be analyzed.

[0004] This detection technology is relevant to various industries, ranging from the food industry and wastewater treatment to pharmaceutical applications and medical devices, where known techniques usually require large sample sizes and time-consuming analytical procedures.

[0005] One example of an application of this measurement technology relates to the detection of analytes in bodily fluids, such as a patient's blood sample. The analyte can be any laboratory test parameter used in bodily fluid analysis that can be detected optically, such as by spectrophotometry. Hemolysis, a source of interference in blood analysis, can affect the measurement of many blood parameters determined in blood parameter analyzers. Consequently, ignoring the level of free hemoglobin in a blood sample can mislead an uninformed individual and, consequently, provide an erroneous diagnosis based on the affected blood parameter values. However, to date, reliably determining the level of free hemoglobin present in the plasma fraction of a whole blood sample has involved a complex process requiring separation of the plasma fraction from cellular components and subsequent analysis of the separated plasma fraction. This process is time-consuming and can be prohibitive in situations where only very small samples are available at a time, such as in neonatal care for continuous monitoring of infant blood parameters. Other methods for measuring components present in the plasma fraction of whole blood include separating the plasma fraction from the cellular components using microfiltration techniques in a microfluidic device and then analyzing the plasma fraction in a dedicated measurement within the microfluidic device. For example, a recent scientific article by Archibong et al., published in Sensing and Bio-Sensing Research 3 (2015), pp. 1-6, discloses a miniature measurement chamber for optically analyzing the plasma fraction separated from a whole blood sample. In this type of device, a miniature microfluidic chamber is attached to the interface of an optical fiber. The bottom of the microfluidic chamber is composed of a porous membrane that allows fluids and chemical compounds to flow inside the device while filtering out unwanted particles. The interior of the microfluidic chamber, which receives the filtrate, can be optically probed by a single optical fiber in a normal-incidence reflecting geometry. However, due to clogging issues, the disclosed device is more useful as a single-use device than for continuous and repeated use, as completely rinsing the sample after measurement can be difficult, or at least very time-consuming and unreliable, with the further risk of cross-contamination between subsequent samples. In addition, in this particular type of device, additional challenges may arise in obtaining quantitative results from optical detection due to pressure-induced deformation of the filter membrane, which causes the optical path used to detect the filtrate to change.

[0006] In another example, in applications in the food industry, such as the dairy industry, most conventional filtration and detection methods, including filter papers, sieves, etc., for visual inspection of residues, spectrometric determination, or bacterial counts, have the aforementioned disadvantages of requiring relatively large sample volumes, involving time-consuming measurement procedures that are harmful to the sample, and being incompatible with comprehensive multi-parameter measurements performed on the same sample. Similar challenges are also encountered in the field of environmental technology, such as wastewater analysis and treatment, where most conventional filtration and detection methods, including filter papers, sieves, etc., are used for spectrometric determination and bacterial counts of residues.

[0007] Filtration-based methods have several disadvantages when used to analyze, for example, whole blood samples. Filter devices inherently rely on the flow of at least the filtrate from the sample supply to the filtrate analysis / measurement chamber through the pores of the filter. In a through-flow geometry, the retentate (here, red blood cells) gradually clogs the filter pores. In a cross-flow geometry, the retentate is guided along the surface of the filter membrane, thereby reducing but not eliminating the clogging problem, especially if the system is intended to be reused (more than 10-100 samples). The cross-flow geometry also leads to friction and shear interactions between the retentate and the filter device surface.

[0008] Improved separation and measurement techniques that address these problems are disclosed in the applicant's co-pending international patent applications WO 2017 / 085162 A1, WO 2017 / 085180 A1 and WO 2019 / 197308 A1, which are incorporated herein by reference.

[0009] Similarly, a particularly challenging application area is the analysis of body fluids in point-of-care devices. Modern point-of-care analyzers for analyzing multiple parameters in body fluid samples, such as those for analyzing arterial blood, are subject to stringent requirements and constraints regarding patient safety, user-friendliness, short measurement times of one minute or less, reliability / reproducibility, accuracy of quantitative output, and compliance with quality management systems and safety directives for medical measurement devices. These requirements and constraints require accurate and compliant results to be obtained with very small amounts of sample fluid (typically less than 100 μl, or even less than 50 μl). Consequently, most advanced point-of-care analyzer systems are designed around automated fluid handling and measurement infrastructure, with a compact sensor assembly at its core. This sensor assembly is intended for repeated use and typically has a sample space defined by sample chamber walls, with a miniaturized, high-precision sensor directly integrated into at least one of the walls. An example of such a sensor assembly for body fluids is disclosed, for example, in European Patent Specification EP 2 147 307 B1. The sensor assembly of EP2147307B1 comprises electrochemical and optical sensor elements and is particularly suitable for simultaneously measuring multiple different parameters in a body fluid sample, such as blood parameters. Therefore, it is expected that new measurement technologies that meet the aforementioned requirements for highly sensitive, simple, and selective detection of analytes in complex fluids should be suitable for integration with such sensor assemblies having a sample channel width in the millimeter range and a sample channel height in the submillimeter range.

[0010] The applicant's aforementioned application WO2019197308A1 describes a device for detecting an analyte in a fluid sample by optical detection, wherein a porous sensor element is disposed in a wall of a sample chamber for holding the fluid sample. The sensor surface has open pores and faces the sample chamber for contact with the fluid sample, and receives at least a continuous portion of the analyte from the complex fluid sample in the pores by diffusion.

[0011] One advantage of the present invention is that when operating a porous membrane device for detecting analytes in complex fluids, the accuracy, reproducibility and reliability of the measurements obtained may be strongly affected by the diffusive transport of the analyte in question from the complex fluid sample into the pores of the porous membrane, where the actual measurement is performed by optical detection.

[0012] Thus, there remains a need for improved devices and methods for detecting analytes in fluids with a rapid and reliable response, which can be implemented in a miniaturized manner and which would facilitate integration into automated point-of-care analyzer systems for bodily fluids. More generally, there remains a need for improved devices and methods for detecting substances in a portion of a complex fluid, such as a whole blood sample, with a rapid and reliable response, which are suitable for miniaturization and integration into a fluid analyzer system, particularly an analyzer system for performing multi-parameter measurements on the same fluid sample.

[0013] Thus, according to one aspect, the present invention aims to provide an improved detection device and / or method that overcomes at least some of the disadvantages of known devices, sensors, systems and / or methods for the specific detection of analytes in continuous fractions of complex fluids, such as for the detection of analytes in the plasma fraction of a whole blood sample. According to another aspect, the present invention aims to provide such a detection device that can be miniaturized for integration with a sensor assembly. Summary of the Invention

[0014] According to one aspect, the present invention relates to a sensor assembly for analyzing a complex fluid sample, the sensor assembly comprising: a sample chamber for accommodating a complex fluid sample, the sample chamber being defined by a chamber wall and having an inlet and an outlet, the inlet and the outlet defining a flow direction from the inlet toward the outlet for fluid processing in the sample chamber; wherein the sample chamber comprises a first sample space and a second sample space, the second sample space comprising a porous membrane sensor element for detecting an analyte; the porous membrane sensor element comprising a porous membrane having a front side defining a sensor surface for contacting the fluid sample, the sensor surface facing the second sample space, the porous membrane comprising a dead-end pore extending from a corresponding opening in the sensor surface into the porous membrane, wherein the pore is configured with respect to the analyte for diffusive fluid communication with the second sample space; wherein the sample chamber further comprises a flow disturbance element arranged upstream of the second sample space and between the first sample space and the second sample space.

[0015] In point-of-care measurement systems (also referred to in the art as "bedside" systems) and similar laboratory environments, blood gas analysis is often performed by users, such as nurses, who may not be trained users in the use of blood gas analyzers. In particular, it has been found that correctly positioning a handheld blood sample container, such as a syringe or capillary tube, at the inlet structure of the blood gas analyzer when drawing a blood sample into the blood gas analyzer is a challenging aspect. Incorrect positioning or alignment of the blood sample container relative to the inlet structure can not only cause disruptive delays and / or frustration in the user's daily workflow, but can even lead to loss of the blood sample or contamination of the blood gas analyzer or its surroundings.

[0016] According to a particular aspect of the present invention, the use of the system / method according to any embodiment herein for point-of-care (POC) measurement of analyte parameters in bodily fluids, in particular in whole blood samples, is proposed.

[0017] In the art, POC measurements are also known as "bedside" measurements. In this context, the term "point-of-care measurement" should be understood to refer to measurements performed in close proximity to the patient, i.e., not in a laboratory. Thus, according to this embodiment, a user of the blood gas analyzer performs measurements on a whole blood sample in a handheld blood sample container near the patient (e.g., in a ward or patient room housing the patient's bed, or in a nearby room in the same hospital department), the blood sample being taken from the patient. In such uses, the expertise level of the users often varies from novice to experienced, so in such an environment, the ability of the blood gas analyzer to automatically output instructions that match the skills of each individual user based on the sensor input is particularly beneficial.

[0018] The sensor assembly can be used to analyze complex fluids comprising continuous and discontinuous portions, and in particular, to selectively detect an analyte in the continuous portion of the complex fluid. The sensor assembly is particularly suitable for miniaturization and / or integration into a fluid analyzer mechanism for measuring multiple analyte parameters, such as in modern arterial blood analyzers.

[0019] The term "complex fluid" as used herein refers to a fluid having a continuous portion and a discontinuous portion, such as a liquid portion and a particle portion. Typically, analyte is a component in the continuous portion of a complex fluid sample. Therefore, the fluid to be analyzed comprises at least the continuous portion comprising the analyte. The fluid to be analyzed may also comprise a discontinuous portion, i.e., a particle portion. The particle portion may comprise, for example, solid particles, debris and other contaminants, biological cells (such as red blood cells) or microorganisms, droplets, bubbles, and combinations thereof. The fluid to be analyzed may be a whole blood sample, the plasma portion of whole blood, spinal fluid, urine, pleura, ascites, wastewater, a pre-prepared fluid for injection of any kind, a fluid with a component that can be detected by optical detection (such as spectrum), or a gas, such as air, a gas containing carbon dioxide, a gas containing carbon monoxide.

[0020] The analyte can be any substance detectable by a suitable detection technique, such as optical detection, as described in further detail below. For example, the analyte can be a subset of molecules that can be present in the continuous phase of the fluid to be analyzed. For example, when analyzing a whole blood sample, the analyte can be a specific drug, and the measurement can be used to determine the drug content in the plasma phase, such as to determine drug uptake and adjust the drug dosage accordingly. In another example of analyzing a whole blood sample, the analyte can be bilirubin, which is used to determine the degree of hemolysis. In another example of analyzing a whole blood sample, the analyte can be carbon dioxide.

[0021] The term "fluid" refers to liquids and / or gases comprising complex fluids comprising a continuous phase and a discontinuous phase, such as a particle phase. Examples of relevant fluids analyzed using embodiments of the present invention include, but are not limited to, body fluids, particularly whole blood samples, the plasma portion of whole blood, spinal fluid, urine, pleura, ascites. Other examples of relevant fluids include wastewater, pre-prepared fluids for injection of any type, fluids with components that can be detected by spectroscopy, or gases, such as air, gases containing carbon dioxide, gases containing carbon monoxide. The term "sample" refers to that portion of fluid used or needed when analyzing with the porous membrane of the present invention.

[0022] The term "whole blood" refers to blood composed of plasma and cellular components. Plasma accounts for approximately 50%-60% of the volume, while cellular components account for approximately 40%-50% of the volume. The cellular components are red blood cells (erythrocytes), white blood cells (leukocytes), and thrombocytes (platelets). The term "whole blood" preferably refers to whole blood from a human subject, but it can also refer to whole blood from an animal. Red blood cells make up approximately 90%-99% of all blood cells. In their undeformed state, they are biconcave discs with a diameter of approximately 7 μm and a thickness of approximately 2 μm. Red blood cells are very flexible, allowing them to pass through very narrow capillaries, which can reduce their diameter to approximately 1.5 μm. A core component of red blood cells is hemoglobin, which binds oxygen for transport to tissues and then releases it and binds carbon dioxide for transport to the lungs as waste. Hemoglobin is responsible for the red color of red blood cells, and therefore blood. White blood cells make up less than 1% of all blood cells. They have a diameter ranging from approximately 6 to approximately 20 μm. White blood cells participate in the body's immune system, for example, fighting bacterial or viral invasions. Platelets are the smallest blood cells, measuring approximately 2 to 4 μm in length and 0.9 to 1.3 μm in thickness. They are cell fragments containing enzymes and other substances important for blood clotting. In particular, they form temporary platelet plugs that help seal cracks in blood vessels.

[0023] The term "blood plasma" or "plasma" refers to the liquid portion of blood and lymph, which comprises approximately half the volume of blood (e.g., approximately 50%-60% by volume). Plasma is cell-free. It contains all of the coagulation factors, particularly fibrinogen, and is approximately 90%-95% water by volume. Plasma components include electrolytes, lipid metabolites, markers such as for infection or tumors, enzymes, substrates, proteins, and other molecular components.

[0024] The term "wastewater" refers to water that has been used, for example for washing, flushing or in a manufacturing process, and therefore contains waste and / or particles and is therefore unsuitable for drinking and food preparation.

[0025] The sample chamber is formed as a channel extending from an inlet to an outlet and includes a first sample space and a second sample space, which are separated from each other by a flow disturbance element. From the direction of the inlet to the outlet, the first sample space is arranged upstream of the flow disturbance element and between the flow disturbance element and the inlet, and the second sample space is arranged downstream of the flow disturbance element. In all embodiments, the flow disturbance element is suitable for causing mixing of the sample with itself upstream of the second sample space. Therefore, the original sample can be prepared in the second sample space regardless of the flow history upstream during the fluid processing in the sample chamber. By presenting the original sample in the second sample space, it is possible to ensure that the analyte concentration in the interface layer of the fluid sample adjacent to the sensor surface of the porous sensor element is representative of the entire fluid sample. Therefore, reliable and reproducible parameter measurements can be obtained from the subsample extracted from the interface layer into the pores of the porous membrane.

[0026] In some embodiments, the flow disturbance element may be configured to force a transition in flow regime, such as from laminar flow to turbulent flow or a similar disturbed flow regime, in the fluid flowing through the sample chamber in a direction from the inlet to the outlet.

[0027] In some embodiments, the flow disturbance element is configured to force a transition in flow regime so as to induce laminar agitation of the fluid sample flowing through the sample chamber in the direction from the inlet to the outlet. Here again, the flow disturbance element enables the fluid to mix with itself downstream of a first sample space of the sample chamber and at least upstream of a second sample space of the same sample chamber. However, in these embodiments, the flow disturbance element is now configured to maintain a laminar flow regime throughout the sample chamber for typical flow rates applied during fluid processing of at least the complex fluid sample to be measured. This embodiment of the sensor assembly is particularly suitable for measuring whole blood samples, including measurements of hemolysis in patients. Thus, excessive shear forces applied to the particulate phase of the whole blood sample, which could otherwise cause undesirable hemolysis and invalidate the hemolysis measurement, can be avoided. By configuring the flow disturbance element such that the induced flow disturbance induces laminar mixing, a representative sample for measurement can be ensured at the interface of the sensor surface in the second sample space, regardless of the flow history through the first sample space upstream of the second sample space during sample chamber filling, without the risk of damaging the fluid sample to be analyzed by excessive shear forces within the fluid sample during fluid processing in the sample chamber.

[0028] Advantageously, the flow disturbance element can be arranged in or at the upstream end of a supply channel connecting the first sample space and the second sample space. Advantageously, the flow disturbance element arranged in or at the upstream end of such a supply channel is configured to force a flow pattern transition, for example, from a laminar flow received from the first sample space to a turbulent flow or a similar disturbed flow pattern downstream thereof. More specifically, in some embodiments, the flow disturbance element is adapted to cause stirring of the fluid flowing through the sample chamber in the direction from the inlet to the outlet, at least within the supply channel connecting the first sample space and the second sample space. Thus, the flow disturbance element enables the fluid to mix with itself after having passed through the first sample space and at least before entering the second sample space. Thus, the likelihood that the porous membrane sensor surface in the second sample space will reliably present a representative fluid sample interface is increased.

[0029] Advantageously, the flow disturbance in the fluid processing flow through the sample chamber is localized and occurs upstream (possibly immediately upstream) of the second sample space. Thus, the flow disturbance element is configured to cause a localized flow disturbance and, in some embodiments, agitate the fluid flowing upstream (possibly immediately upstream) of the second sample space while the flow regime for fluid processing in the second sample space is also laminar.

[0030] Operating the sensor assembly generally includes the steps of filling the sample chamber with fluid by flowing a quantity of fluid from the inlet through the sample chamber to the outlet, stopping the flow when filling is complete, and thereby taking a measurement of the fluid sample present in the sample chamber.

[0031] The analyte is extracted from the fluid sample into the porous membrane by diffusion. The analyte can then be detected using a suitable detection mechanism, such as optical detection described below. The term "detection" as used herein is considered to include simple qualitative detection and / or quantitative measurement of the presence of a given analyte, such as a measurement for determining the concentration of an analyte in a complex fluid sample. The pores of the porous membrane are in diffusion fluid communication with the sample chamber. The pores are configured relative to the analyte for diffusion fluid communication between the fluid in the pores and the fluid sample in the second sample space of the sample chamber. Thus, the pores are configured to exchange the analyte with a continuous portion of the complex fluid sample in the sample chamber by diffusion transport while preventing much larger particles of the discontinuous phase of the complex fluid sample from entering the pores.

[0032] As described above, operation of a measurement device for performing measurements on a given fluid sample in a sample assembly according to embodiments of the present invention typically includes a fluid handling step, such as a flushing step, i.e., a flushing fluid is passed through the sample chamber in a flow direction from the inlet to the outlet in order to remove any pre-existing fluid sample and any contaminants, such as contaminants originating from the pre-existing fluid sample, from the sample chamber. Furthermore, operation of a measurement device using a sensor assembly typically includes a step of calibrating the device by performing measurements on a calibration fluid present in the sample chamber. Consequently, operation of the sample assembly includes frequent fluid handling operations, such as filling, draining, and refilling the sample chamber by passing different fluids through the sample chamber in a flow direction from the inlet to the outlet.

[0033] Most preferably, the first and / or second sample spaces are configured for laminar flow during fluid processing in the sensor assembly. In order to achieve reliable and reproducible fluid displacement performance, laminar flow through the sample chamber is generally required to detect one or more analytes. Therefore, it is also desirable to maintain a laminar flow state during fluid processing in the sensor assembly. However, in contrast, the flow disturbance element causes mixing of the fluid sample with itself immediately upstream of the second sample space. Preferably, the flow disturbance is confined to a portion of the sample chamber between the first and second sample spaces, i.e., downstream of the first sample space and upstream of the second sample space. In addition, during fluid processing in the sensor assembly in the first sample space, a laminar flow state is preferably maintained while maintaining flow disturbances at the flow disturbance element downstream of the first sample space. In addition, during fluid processing in the sensor assembly in the second sample space, a laminar flow state is preferably also maintained while maintaining local flow disturbances at the flow disturbance element upstream of the second sample space.

[0034] By providing a flow-disturbing element between the first and second sample spaces, arranged upstream of the second sample space, measurement artifacts resulting from irregular losses in the boundary layer of the fluid sample contacting the porous membrane sensor surface in the second sample space can be increasingly reduced or even avoided. For example, boundary layer losses and the effects of cross-contamination of the fluid sample in a very thin boundary layer near the channel wall, for example due to tiny remnants of pre-existing fluid adhering to the chamber wall and / or to the portion of the porous membrane sensor surface facing the second sample space, can be reduced or even eliminated.

[0035] Furthermore, according to some embodiments of the sensor assembly, the porous membrane sensor element is configured for detecting high molecular weight analytes.

[0036] In the context of this application, the term "high molecular weight" refers to a molecular weight of 10,000 Da or more, such as 30,000 Da or more, or such as 50,000 Da or more. An example of detecting high molecular weight analytes in continuous fractions of a complex fluid is detecting hemolysis in a whole blood sample.

[0037] A particular advantage of the present invention is that it realizes that when analyzing high molecular weight components in a complex fluid sample, diffusion transport near the chamber wall, which includes the sensor surface, is particularly important. Without being bound by theory, one reason for this surprising measurement sensitivity when analyzing high molecular weight components in complex fluids may be a "labyrinth effect," which prevents these high molecular weight components in the continuous phase from diffusing toward the chamber wall through the "maze" formed by the large particles in the discontinuous phase. Due to this labyrinth effect, the diffusion rate of the high molecular weight components through the discontinuous phase particles can be reduced to such an extent that the analyte for analysis in the porous membrane is substantially drawn out of the boundary layer of the continuous phase contacting the sensor surface, because the discontinuous phase effectively prevents the analyte from diffusing into the pores of the sensor surface from deeper regions of the complex fluid sample away from the sensor surface.

[0038] By providing a flow disturbance element upstream of the second sample space, this problem is at least reduced, if not eliminated. By means of the flow disturbance element, the complex fluid sample is agitated immediately upstream of the second sample space and provided with a complex fluid sample having a representative concentration of high molecular weight analytes in the boundary layer for contacting the porous membrane sensor surface. Without being bound by theory, this may be attributed to a reduction in apparent diffusion losses of high molecular weight analyte components in the very thin boundary layer of the continuous portion of the complex fluid sample, which may otherwise occur due to microscopic remnants of pre-existing fluid sample, flushing fluid and / or calibration fluid adhering to the chamber walls upstream of the second sample space all the way from the inlet. This results in more reliable and reproducible measurements when analyzing high molecular weight components in the continuous portion of the complex fluid.

[0039] Furthermore, according to some embodiments of the sensor assembly, the first sample space includes one or more additional sensor elements for detecting corresponding additional analytes. Thus, the sensor assembly is suitable for simultaneously analyzing multiple analytes, including an analyte detectable by the porous membrane sensor element in the second sample chamber and additional analytes detectable by one or more additional sensor elements arranged in the first sample space. By arranging the additional sensor elements in the first sample space upstream of the flow-disturbing element, this is achieved without interfering with the measurement quality of the analyte detected by the porous membrane sensor element in the second sample space downstream of the flow-disturbing element.

[0040] Furthermore, according to some embodiments of the sensor assembly, the flow disturbance element is formed as an abrupt change in the sample chamber geometry. For example, the flow disturbance element is configured to induce flow disturbance by a sudden change in the flow direction through the sample chamber from the inlet to the outlet. According to some embodiments, the sample chamber can be a channel extending from the inlet to the outlet, comprising a sharp bend, wherein the second sample space is arranged downstream of the sharp bend. According to advantageous embodiments, a bend can be considered a sharp bend if the radius of curvature of the channel's centerline after the bend is less than the width of the channel at the bend. According to advantageous embodiments, a bend can also be considered a sharp bend if the minimum radius of curvature along the main direction of the sample chamber from the inlet to the outlet is less than the width of the channel at the bend. Sharp bends or similar abrupt changes in the channel direction have the advantage over other flow disturbance elements that dead zones in the wake of the flow disturbance element can be more easily avoided. Such dead zones are undesirable because they can attract bubbles, droplets, and similar reminiscent contaminants that are difficult to rinse away, and can contaminate subsequent samples, thereby corrupting measurements of such subsequent samples.

[0041] Furthermore, according to some embodiments of the sensor assembly, the flow disturbance element is formed as a connecting nozzle connecting the supply channel of the second sample space to the downstream end of the first sample space. Thus, an efficient and simple realization of a sudden change in channel direction can be achieved.

[0042] Furthermore, according to some embodiments of the sensor assembly, the flow-disturbing element is formed as a connecting nozzle arranged at an angle relative to the main axis of the sample channel forming the first sample space, wherein the angle is at least 30 degrees, at least 40 degrees, at least 50 degrees, at least 70 degrees, or typically about 90 degrees relative to the main axis. Thus, a sudden change in channel direction can be further efficiently and simply achieved.

[0043] Furthermore, according to some embodiments of the sensor assembly, the flow disturbance element is located immediately upstream of the second sample space, at a distance of at least 0.3 mm, 0.5 mm, 1 mm, and / or at most 3 mm, at most 5 mm, or at most 10 mm from the inlet opening of the second sample space. Thus, flow disturbance is achieved immediately upstream of the second sample space. Advantageously, according to some embodiments, the first sample space is formed as a channel having a top wall, a bottom wall, and side walls connecting the top and bottom walls, thereby defining a substantially rectangular cross-section when viewed perpendicular to a main direction of the first sample space from the inlet to the outlet. Advantageously, the rectangular cross-section of the first sample space has a width in the range of several millimeters, e.g., at most 10 mm, at most 5 mm, or at most 3 mm, and at least 1 mm or at least 2 mm, e.g., about 2.4 mm, as viewed in a transverse direction parallel to the top and bottom walls; and a height in the submillimeter range, e.g., less than 1 mm, less than 0.8 mm, and less than 0.5 mm, at least 0.1 mm, or at least 0.2 mm, or at least 0.3 mm, e.g., about 0.4 mm, as viewed in a direction perpendicular to the top and bottom walls. Furthermore, advantageously, the flow-disturbing element is a nozzle forming a T-junction or an L-junction at the downstream end of the first sample space. Preferably, the nozzle is connected at its downstream end to one of the top and bottom walls of the first sample space.

[0044] Furthermore, according to some embodiments of the sensor assembly, the sensor surface is planar.

[0045] Furthermore, according to some embodiments of the sensor assembly, the sensor surface is arranged parallel to the flow direction from the inlet to the outlet for fluid processing in the second sample space of the sample chamber. This allows for efficient contact between the sensor surface and the sample surface. Furthermore, this allows for smooth and efficient replacement of fluid contacting the sensor surface during fluid processing operations. Furthermore, this reduces cross-contamination.

[0046] Furthermore, according to some embodiments of the sensor assembly, the second sample space has a cylindrical shape defined by a top wall, a bottom wall opposite the top wall, and a peripheral wall connecting the top and bottom walls; the supply orifice is arranged at the upstream end of the second sample space, i.e., as viewed toward the flow disturbance, toward the first sample chamber, and toward the inlet; and the discharge orifice is arranged at its downstream end, i.e., as viewed toward the outlet. Preferably, the porous membrane sensor element is arranged in the top wall. According to some embodiments, the cylindrical shape can have a circular cross-section or an elliptical cross-section, as viewed in a section parallel to the sensor surface.

[0047] Furthermore, according to some embodiments of the sensor assembly, the supply orifice and the discharge orifice are arranged in the peripheral wall. Preferably, the supply orifice and the discharge orifice are arranged opposite each other. Thus, when performing fluid handling operations, a simple flow pattern through the second sample space is achieved. This further enables smoother and more efficient replacement of fluid contacting the sensor surface during fluid handling operations. Furthermore, this reduces cross-contamination.

[0048] Furthermore, according to some embodiments of the sensor assembly, the height of the second sample space, viewed from the top wall toward the bottom wall, is less than half, less than one-third, less than one-fifth, or even less than one-tenth of the lateral dimension of the second sample space. Consequently, a smaller volume of fluid sample is required without compromising the quality of measurements performed in the porous membrane sensor element. This feature further benefits from the present invention's insight that measurements in porous membrane sensor elements rely on diffusional exchange of analytes with a relatively thin boundary layer of a complex fluid sample contacting the sensor surface, particularly with respect to high molecular weight analytes.

[0049] Furthermore, according to some embodiments of the sensor assembly, the bottom wall is curved to reduce the distance between the bottom wall and the top wall in a central portion of the second sample space compared to a peripheral portion of the second sample space. Preferably, the porous membrane sensor element is arranged in the top wall. Preferably, in this embodiment, the porous membrane sensor element is planar. The bottom wall may be curved to bulge towards the top wall at least in a direction from the supply orifice to the discharge orifice, such that the bottom wall is closer to the top wall in the central portion than at the supply / discharge orifice. Preferably, the bulge is gradual to avoid differences in the presence of different fluids (e.g. flushing / calibration) in the sample chamber. Thus, further reduced sample volumes can be achieved without compromising measurement quality, while further achieving smooth flow patterns for efficient fluid handling operations, thereby further reducing the risk of any of the aforementioned complications during fluid handling operations.

[0050] Furthermore, according to some embodiments of the sensor assembly, the porous membrane sensor element is configured to detect the analyte by optical detection, thereby providing a highly sensitive detection mechanism.

[0051] The terms "optical" and "light" and related terms generally refer to electromagnetic radiation in the visible, infrared, and ultraviolet spectral ranges: the term "visible" generally refers to electromagnetic radiation with a wavelength in the range of 400nm-700nm; the term "infrared" generally refers to electromagnetic radiation with a wavelength in the range of 700nm-1mm, with typical subranges being "near infrared" approximately 700nm-3μm, "mid infrared" 3μm-50μm, and "far infrared" 50μm-1mm; the term "ultraviolet" or "UV" generally refers to electromagnetic radiation with a wavelength in the range of 10nm-400nm, with typical subranges being "near ultraviolet" 300nm-400nm, "mid ultraviolet" 200nm-300nm, and "far ultraviolet" 122nm-200nm. The skilled person will understand that the usefulness of the spectral ranges mentioned for a given sensor element, and in particular for a given translucent film material, will depend on the spectral ranges and the compatibility of the materials used to propagate the input and output light through these materials.

[0052] Furthermore, according to some embodiments of the sensor assembly, the porous membrane is a translucent membrane, wherein the porous membrane sensor further comprises: a reflective layer arranged on a front side of the translucent membrane; an optical input port connected to a rear side of the translucent membrane, the rear side facing away from the front side, the optical input port being adapted to supply detection light to a detection region of the translucent membrane through the rear side; and a light output port connected to the rear side of the translucent membrane, the light output port being adapted to collect an optical response from the translucent membrane through the rear side;

[0053] The term "translucent" refers to the property of a material that allows light to pass through it. The term "transparent" refers to the property of a material that allows light to pass through the material without being scattered. The term "transparent" is therefore considered a subset of the term "translucent".

[0054] The optical input port is configured to supply probe light into the translucent membrane through the rear side. The optical output port is configured to collect an optical response to the probe light from the translucent membrane through the rear side. By injecting the probe light and collecting the optical response from the rear side of the translucent membrane, a compact design is achieved, allowing the sensor element to be integrated into a miniaturized sample assembly with a very small sample chamber designed for analyzing very small amounts of sample fluid.

[0055] The back side of the translucent film is typically parallel to the front side. An additional transparent backing may be applied to the back side to provide mechanical support to strengthen / reinforce the translucent film from the back side. The backing may be a transparent filler that fills the gap between the translucent film and other optical components of the sensor element (e.g., input and / or output ports). The sensor element is typically held together in a mechanical mount, such as a sensor element housing. Any gaps between the back side of the translucent film and any other optical components may be filled with a transparent filler. Preferably, according to some embodiments, the refractive index of the transparent filler matches that of the translucent film within a tolerance range, for example, within 5%, preferably within 2%, and most preferably within 1%.

[0056] As described above, the porous membrane sensor element has a sensor surface for contacting the fluid to be analyzed. The sensor surface is formed on the front side of the translucent membrane, and a reflective layer is applied to the front side. The translucent membrane includes small holes, preferably dead-end holes, that extend from the front side through the reflective layer into the translucent membrane. Each small hole has an opening through which it can communicate with the fluid space on the front side of the translucent membrane. Therefore, the holes penetrate the reflective layer to allow fluid communication between the holes and the fluid space. These holes extend from the corresponding opening on the front side into the translucent membrane in a direction toward the back side. The holes are preferably "dead-end", meaning that the holes terminate within the translucent membrane. Dead-end holes do not pass all the way through the translucent membrane to reach any common reservoir or receiver on the back side or within the membrane. These holes are only in fluid communication with the fluid space on the front side of the translucent membrane. Note that in some embodiments, the dead-end holes can be intersecting, and at least some of the holes can thus be connected to each other to form an X-shape, Y-shape, V-shape, or similar interconnected shape. This configuration is also considered dead-end because the holes are only filled from the front side and there is no significant net mass transfer through the holes during operation, even if they intersect with each other.

[0057] The translucent film can be made from a transparent polymer film with holes made therein, using the so-called track etching technique disclosed, for example, in co-pending international patent applications WO 2017 / 085162 A1 and WO 2017 / 085180 A1, which are incorporated herein by reference.

[0058] The hole forms a vial / test tube for selectively receiving the analyte from the first part of the fluid, particularly by diffusion / diffusion transmission, and effectively preventing the particle part from entering the hole. These vials / test tubes are placed at least in the detection area for the effective interaction of the detection light and the analyte. The size of the opening of the hole makes the particulate part of the fluid to be analyzed remain outside the hole, while allowing the analyte from another part (such as the continuous part) to enter the translucent membrane through the hole, so that the detection light injected from the input port can interact with the analyte, thereby detecting the analyte by optical detection. By appropriately determining the opening size of the front side hole, it is possible to prevent, for example, the red blood cells of the whole blood sample on the sensor surface from entering the hole, while allowing the relevant components in the plasma part of the whole blood sample to enter the hole, wherein the relevant components are substances present in the plasma part of the whole blood sample (or more generally, substances present in the relevant part of the fluid sample), and they will be measured / detected using the sensor.

[0059] This configuration allows for gentle extraction of small but representative analyte fractions from complex fluids and their efficient exposure to the probe light in the detection area with a high degree of overlap. This separation is achieved in a particularly simple and rapid manner, as the detection area is arranged directly on the surface of the translucent membrane, the pores penetrate the membrane directly, and the distance from their corresponding openings in the sensor surface to the detection location is relatively short, thus facilitating a particularly rapid diffusion exchange of the sample.

[0060] Typical cross-sectional dimensions of the pores are in the micrometer and submicrometer range down to about 100 nm. The transport of the analyte into and out of the pores is achieved by diffusion. For efficient operation, the pores are filled with a priming fluid, which is preferably filled into the pores in a priming step, for example before performing the first detection measurement. The priming fluid does not affect the fluid to be analyzed. Therefore, the priming fluid must be compatible with the fluid to be analyzed. Advantageously, the priming fluid can be a flushing fluid, such as an aqueous buffer solution, which can also be used to flush the sample chamber during filling, emptying and refilling to replace the sample of the fluid to be analyzed. The flushing fluid can also be a reference fluid or a calibration fluid.

[0061] Advantageously, according to some embodiments, the wells are filled with a liquid. Filling the wells with a known liquid allows a subsample representing the relevant components of the fluid to be analyzed to be extracted into the wells solely by diffusion. This provides for rapid, efficient, and well-controlled exchange of analytes into and out of the optical detection area via the wells. Advantageously, according to some embodiments, the liquid is an aqueous solution. This is particularly useful for detecting water-soluble analytes. Alternatively, it is conceivable that the wells are filled with a non-aqueous liquid, which is particularly useful, for example, when the fluid to be analyzed is also a non-aqueous liquid.

[0062] During operation, the front side of the translucent membrane can be in contact with, for example, a whole blood sample or a fluid. The pores in the translucent membrane communicate with the whole blood sample or fluid through openings in the front side. The pore openings are sized to selectively extract a subsample of the plasma phase of the whole blood sample, or a subsample of the fluid containing the analyte. No red blood cells can enter the pores through the openings in the front side of the translucent membrane. Any material larger than the pore diameter cannot enter the pores, which excludes, for example, any debris contained in the fluid. As described above, the pores are preferably dead-ended, communicating only with the front side of the translucent membrane. That is, the subsample is extracted for optical detection within the pores and, after measurement, is discharged again through the same openings in the front side of the translucent membrane. The subsample volume corresponds to the total internal volume of the pores. No filtrate undergoes filtration or net mass transfer through the pore-containing layer—neither enters any conventional filtrate receiver nor reaches any filtrate outlet. Therefore, only the subsample contained in the pores is optically detected. The reflective layer optically separates the optical detection area in the translucent membrane from the fluid volume containing the whole blood sample or fluid. By optically separating the detection region from the fluid volume, any contribution to the detection signal from intact red blood cells in the whole blood sample or debris in the fluid is effectively suppressed. Therefore, the measurement is specific to the amount of analyte in the fluid.

[0063] A small subsample with a representative content of the relevant components can be transferred to the well in any suitable manner. The small dead-end well allows a subsample for optical detection to be extracted very efficiently and quickly from a whole blood sample or fluid by means of capillary forces and / or diffusion through an opening in the front side. In a typical operating mode, the front side surface is contacted with a flushing fluid before the front side of the translucent membrane is brought into contact with the whole blood sample or fluid to be analyzed. Therefore, the well is pre-filled with a liquid that is compatible with the whole blood sample or fluid, in particular if the fluid is whole blood, the well is pre-filled with a liquid that is compatible with plasma, such as an aqueous solution commonly used for flushing, calibration and / or quality control purposes in blood analyzers. A typical flushing liquid used for cleaning in, for example, whole blood analyzer systems can be used as such a liquid. The flushing liquid is a liquid containing K corresponding to a concentration of human plasma. + ,Na + ,Cl - ,Ca 2+ ,O2,pH,CO2 and HCO 3- When the whole blood sample or fluid is then brought into contact with the front surface primed with the plasma-compatible liquid / fluid-compatible liquid, a representative subsample of the components in the plasma phase of the whole blood sample or fluid is extracted and transferred in a very efficient and gentle manner by diffusion of the relevant components into the pre-filled wells. In particular, any concentration gradient of analyte content between the fluid and the reference liquid in the wells drives the diffusional transfer, thereby producing a subsample of analyte concentrations in the wells that are representative of the analyte concentration in the fluid.

[0064] The subsample volume corresponds to the total internal volume of the wells. During the measurement, no filtrate undergoes filtration and net mass transfer through the well-containing layer—neither into any common filtrate receiver nor into any filtrate outlet. Optical detection is then performed only on the subsample contained within the wells. Confining the input light to the translucent membrane optically separates the optical detection from the fluid space containing the whole blood sample or fluid. By optically separating the optical detection from the fluid space, the contribution of intact red blood cells in the whole blood sample or debris in the fluid to the detection signal is effectively suppressed. Consequently, the measurement is specific to the analyte content in the fluid.

[0065] The contents of the aperture can be conveniently optically probed from the rear side of the translucent membrane, or more generally, from the side of the reflective layer facing the translucent membrane, wherein the reflective layer on the front side optically separates the optical probe region encompassing the aperture from the fluid contacting the front side of the translucent membrane. The reflective layer is adapted to reflect light reaching the reflective layer from the rear side of the translucent membrane, thereby preventing the probe light from reaching and interacting with the fluid on the front side of the translucent membrane. Thus, optical probing is selectively performed only on a subsample within the aperture.

[0066] Furthermore, according to some embodiments, the sensor assembly further comprises a light source coupled to the optical input port, wherein the light source is configured to emit detection radiation. Furthermore, according to some embodiments, the sensor assembly further comprises a detector coupled to the optical output port, wherein the detector is configured to detect light emitted from the detection region in response to illumination of the detection region by the light source via the input port, and wherein the detector is adapted to generate a signal representative of the detected light. The light source can be any light source that transmits light in a region where the analyte in the well absorbs light, or otherwise provides a light-stimulated response to enable the system to operate. Due to their advantages in terms of size, weight, efficiency, etc., light-emitting diodes are preferred for embodiments intended for miniaturization and / or integration into an assembly. The detector can be any optical detection device adapted to detect an optical response received from the optical output port and to analyze the optical response to generate an output signal representative of the analyte to be detected. Advantageously, according to one embodiment, the detector can comprise a spectrophotometer, and the optical detection device can be configured to perform spectrophotometric analysis of the light emitted from the detection region. This allows for resolution of the spectral signatures of one or more relevant components in the light emitted from a subsample in the detection region. For the sake of miniaturization and compactness, such as in the case of point-of-care devices, the detector can include a photodiode or spectrometer capable of detecting absorption across the entire spectrum. Alternatively, an array or diodes can be used, each emitting light at a different wavelength, with the photodiode acting as the detector. The diodes can be multiplexed to emit light at different time intervals. The absorption is then detected by comparing the light emitted by the diodes during that specific time interval with the light detected by the photodiodes.

[0067] The following examples disclose advantageous rules and ranges for determining pore sizes, in particular for use in sensor elements for the optical detection of body fluids.

[0068] Furthermore, according to some embodiments of the sensor element, the cross-sectional dimension of the pore opening is about 1 μm or less, about 800 nm or less, preferably about 500 nm or less, or even about 400 nm or less. The cross-sectional dimension of the pore opening is preferably adapted to balance size selectivity (smaller pore opening diameter) and rapid exchange of subsample / analyte (larger pore opening diameter)—depending on the application. For example, the given values are particularly useful for the analysis of body fluids, such as whole blood, where the analyte is contained in the plasma fraction.

[0069] Furthermore, according to some embodiments of the sensor element, the cross-sectional dimension of the pore opening is at least 200 nm. The cross-sectional dimension of the pore opening is preferably tailored to balance size selectivity (smaller pore opening diameter) and rapid exchange of subsample / analyte (larger pore opening diameter), depending on the application. For example, this range of values is particularly suitable for analysis of bodily fluids, such as whole blood containing analytes in the plasma fraction.

[0070] Furthermore, according to some embodiments of the sensor element, the length of the pore in the axial direction along the pore is less than 100 μm, less than 50 μm, and preferably less than 30 μm. The pore length is preferably adjusted to balance the desire to provide an increased sample volume for interaction with the optical detection field in the detection region (longer pore length) and rapid sample / analyte exchange (shorter pore length), depending on the application. The given values are particularly useful for analyzing body fluids, such as whole blood containing analytes in the plasma portion of a whole blood sample.

[0071] Furthermore, according to some embodiments of the sensor element, the length of the pore in the axial direction along the pore is at least 1 μm, at least 2 μm, at least 5 μm, and preferably at least 10 μm. The pore length is preferably adjusted to balance the desire to provide an increased sample volume for interaction with the optical detection field in the detection region (longer pore length) and rapid sample / analyte exchange (shorter pore length), depending on the application. The given values are particularly useful for analyzing body fluids, such as whole blood, where the analyte is contained in the plasma portion of a whole blood sample.

[0072] Furthermore, according to some embodiments of the sensor element, the pore is straight. A straight pore facilitates efficient transport through the length of the pore, thereby enabling rapid subsample / analyte exchange.

[0073] Furthermore, according to some embodiments of the sensor element, the pores are track-etched pores formed by exposing the translucent membrane to directional ion bombardment followed by chemical etching. Track etching is particularly suitable for forming straight, narrow, deep pores, such as those of the dimensions described above. These pores can be formed by, for example, a unidirectional arrangement produced by unidirectional ion bombardment exposure. Alternatively, multidirectional pore arrangements can be formed by providing multidirectional ion bombardment exposures from different directions. Thus, before performing the etching step, the pore arrangement can be created / defined, for example, by one or more directional ion bombardment exposures.

[0074] Suitable translucent membranes can be made, for example, of transparent polymer films with so-called track-etched holes, similar to those available from IT4IP SA (IT4IP SA / avenue Jean-Etienne Lenoir 1 / 1348 Louvain-la-Neuve / Belgium), with the modification that the holes are closed at one end. The through-holes in the membrane can be closed, for example, by laminating a backing plate to the back side of the porous membrane, or by slowing down the ions so that the ion bombardment tracks and the holes etched along these tracks stop in the transparent polymer film to form dead-end holes. The membrane is usually supported by a rigid transparent element to provide sufficient mechanical strength for the translucent membrane.

[0075] The translucent membrane should preferably be made of a material that does not absorb light and should be capable of producing dead-end pores in the material, for example, by track etching. Suitable materials for this purpose are, for example, polyethylene terephthalate (PET or PETE) or its analogs (polyethylene terephthalate polyester (PETP or PET-P)) or polycarbonate (PC). The translucent membrane can include a hydrophilic coating, such as polyethylene glycol (PEG), to enhance diffusion into the pores. The hydrophilic coating can be selected to configure the sensor element for a specific operating mode of the sensor element. In some operating modes, once used, the sensor element will never dry out, so it only needs to be hydrophilic at startup. For other operating modes of the sensor element, a coating is applied that remains permanently hydrophilic throughout the life of the sensor element. This allows for an operating mode that allows the sensor element to dry out between subsequent uses while still maintaining rapid subsample extraction from a liquid sample present on the sensor surface. Thus, even if the sensor element is allowed to dry out between uses, a rapid measurement turnaround from contacting the sensor surface with the liquid sample to obtaining an optical detection result can be achieved.

[0076] Advantageously, according to some embodiments of the sensor element, at least within the detection region, the porosity of a given volume of the translucent membrane including the pores is between 50% and 5% by volume, between 30% and 10% by volume, or approximately 15% by volume. The porosity can be characterized by the volume of voids created by the pores in the translucent membrane, i.e., the pore volume, where the pore volume refers to the volume of the translucent membrane penetrated by the pores. This volume is defined as the volume between the frontal region where the pores are distributed and the same parallel region extending into the translucent membrane at the maximum depth of penetration of the pores into the membrane when viewed in a vertical direction perpendicular to the sensor surface.

[0077] Porosity can also be characterized by the integrated pore volume, which is equal to the subsample volume available for optical detection. The pore volume can be conveniently expressed as the equivalent pore volume depth DELTA, which is the pore volume per corresponding frontal area over which the pore openings are distributed. Therefore, the porosity of a semitransparent membrane can be converted into the equivalent pore volume depth DELTA as follows. The pores with openings within a given frontal area a have a total pore volume V. The equivalent pore volume depth is then calculated as the total pore volume divided by the given frontal area: DELTA = V / A.

[0078] Advantageously, according to some embodiments, the equivalent pore volume depth DELTA is less than 20 μm, or less than 15 μm, or less than 10 μm, or in the range of 3 μm to 5 μm, wherein the equivalent pore volume depth DELTA is defined as the total volume V of the pores divided by the frontal area A over which the pore openings are distributed. In this way, a small subsample with a representative concentration of the relevant component is obtained. The small subsample volume is advantageous in facilitating a rapid subsample exchange, thereby reducing the response time of the sensor element and the cycle time of measurements performed using the sensor element. Small subsample volumes are more desirable in order to avoid boundary layer depletion effects of the plasma portion of the whole blood sample close to the front side of the translucent membrane. Otherwise, such depletion effects may occur in small stationary samples, where, if the equivalent pore volume depth exceeds a critical value, for example, red blood cells may hinder the effective diffusion exchange of the relevant components from the whole blood sample volume to the boundary layer on the front side of the translucent membrane.

[0079] Preferably, the equivalent pore volume depth DELTA is at least 1 μm, alternatively at least 2 μm, or in the range of 3 μm to 5 μm, wherein the equivalent pore volume depth is as defined above. Larger subsample volumes are ideal for achieving better signal-to-noise levels because they facilitate optical detection of relevant components in plasma.

[0080] Furthermore, according to some embodiments, a beneficial compromise between reducing response time, reducing cycle time and / or avoiding depletion effects in small stationary whole blood samples or fluids and the required or desired signal-to-noise ratio is found for an equivalent pore volume depth DELTA in the range of 1 μm to 20 μm, preferably in the range of 2 μm to 10 μm or in the range of about 4 μm to 5 μm.

[0081] Furthermore, according to some embodiments of the sensor element, the inner wall surface of the pores is hydrophilic, for example, coated with a hydrophilic coating. This enables efficient capillary-driven filling of the dry pores with liquid. Furthermore, the hydrophilic coating prevents certain hydrophobic substances, such as hydrophobic dyes, hemoglobin, and other proteins, from depositing within the pores, which would otherwise cause gradual fouling of the sensor, which is difficult to remove with aqueous solutions.

[0082] Advantageously, according to some embodiments, the reflective layer is made of metal. Such metal coatings can be applied in a relatively cost-effective and well-controlled manner and have sufficient reflectivity.

[0083] Advantageously, according to some embodiments, the reflective layer is made of platinum, palladium, or an alloy comprising platinum or palladium as a main component. These materials exhibit good reflectivity in the spectral range of the electromagnetic spectrum (deep violet to blue) that is relevant, for example, for detecting certain substances (e.g., free hemoglobin) by absorbance detection. In addition, these materials are biocompatible and do not, for example, introduce artificial hemolysis. Furthermore, these materials are generally chemically stable, particularly in the chemical environment of biological fluids, such as whole blood samples or any of the aforementioned body fluids.

[0084] Alternatively, according to some embodiments, the reflective layer can be made of silver or aluminum. Further advantageously, according to some embodiments, the surface of the reflective layer facing the sample volume is encapsulated by an additional passivation layer, thereby increasing the lifetime of the device, in particular when silver or aluminum is used as the material for the reflective layer. Suitable passivation can be made, for example, of a thin SiO2 layer, which is preferably made transparent and must be thin enough not to obstruct the opening of the pores. These materials can also provide good reflectivity in the relevant spectral range (red) and are biocompatible and chemically stable in the environment.

[0085] Advantageously, according to some embodiments, the thickness of the reflective layer is between 10 nm and 100 nm, depending on the metal used. Such a layer thickness allows the reflective layer to be applied by evaporation techniques without clogging the aperture opening at the sensor surface. At the same time, the layer thickness must be sufficient to provide sufficient attenuation of the light propagating into the sample volume in order to ensure enhanced optical separation between the detection area and the sample volume containing the fluid to be analyzed (e.g., a whole blood sample). Preferably, within the spectral range of detection, i.e., within the spectral range that generates a signal representing the relevant component, the transmitted light is less than 5%, less than 1%, or even less than 0.1%. For example, for measuring hemoglobin in the plasma portion of a whole blood sample, suitable spectral ranges are from 380 nm to 700 nm, from 380 nm to 450 nm, from 400 nm to 430 nm, or about 416 nm.

[0086] According to another aspect of the present invention, a method for optically detecting an analyte, such as hemoglobin, in a fluid is provided. The method implements the steps of providing a fluid sample in a sample chamber and optically detecting an analyte in the fluid sample, as discussed in the disclosure of the sensor assembly and system, and achieves at least the same advantages as discussed with respect to the various embodiments.

[0087] According to some embodiments, a method for detecting an analyte in a complex fluid sample comprises the following steps: providing a sensor assembly as described above; contacting a sensor surface of a porous membrane sensor element with a reference liquid so as to fill the wells with the reference liquid; contacting the sensor surface with a sample of the complex fluid to be analyzed; waiting for a diffusion time to allow the analyte in the complex fluid to diffuse into the wells and stabilize; injecting input light into a detection region from the back side of the porous membrane; collecting light emitted from the wells toward the back side of the porous membrane in response to the input light, thereby optically detecting the fluid within the wells; and determining the analyte level in the complex fluid based on the results of the optical detection. Preferably, the reference liquid is an aqueous solution compatible with the fluid, particularly an aqueous solution compatible with the portion of the fluid that may enter the wells, such as a liquid used for flushing, calibration, and / or quality control. Advantageously, the analyte is optically detected in the wells by a color change due to the presence of a representative amount of the analyte in the extracted subsample. Advantageously, according to some embodiments, the optical detection comprises spectrophotometric analysis of light emitted from the wells as an optical response to the detection input light. Advantageously, according to some embodiments, the optical detection is a measurement of absorbance. This has the advantage of a relatively simple yet effective device. Specifically, the method includes a fluid processing step for contacting the sensor surface of the porous membrane sensor element with a complex fluid sample to be analyzed. These fluid processing steps include causing the complex fluid to be analyzed to flow through the inlet of the sample chamber, through the first sample space, through a connecting supply channel including a flow disturbance element, the connecting supply channel connecting the first sample space with the second sample space, through the second sample space, and through the outlet until a predetermined criterion for determining that the sample chamber is filled is met. The criterion can be determined, for example, by appropriate fluid interface detectors arranged at the inlet and outlet of the sample chamber. The flow of the complex fluid through the sample chamber is performed so that at least the flow through the first and second sample spaces is maintained in a laminar state, while the flow through the connecting channel exhibits a flow disturbance at the flow disturbance element immediately upstream of the second sample space.

[0088] Although the invention is primarily described herein with reference to its use in the context of blood analysis, those skilled in the art will appreciate that the invention may be applied in an equivalent manner in other contexts without departing from the scope of the invention.

[0089] For example, the sensor element can be used in a reading device for color production / consumption determination. The advantage of such a device is that there is no need to perform a separation step in order to produce plasma before the determination. For example, the following types of determinations can be performed with a device including a sensor element according to an embodiment of the present invention: a sandwich determination, in which a receptor ligand can be bound inside a membrane channel; an assay in which a portion is bound in a pore, such as a bromocresol green albumin assay, which uses bromocresol green (BCG) to form a specific colored complex with albumin. The color intensity measured at 620 nm is proportional to the albumin concentration in the liquid; an enzyme activity assay, such as an aspartate aminotransferase (AST) activity assay kit, in which the transfer of an amino group from aspartic acid to α-ketoglutarate results in the production of glutamate, thereby producing a colorimetric (450 nm) product proportional to the AST enzyme activity present.

[0090] Sensor elements can also be used in non-medical applications, such as monitoring tasks in beer brewing, wastewater analysis, food testing, and dye production. In beer brewing, precise color is required. Sensor elements can be used to determine whether the beer has the desired color by measuring the liquid and comparing the reading with a liquid of the correct color. Wastewater can be analyzed for the presence of a certain component. In food testing, liquids such as milk, juice, and other slurries can be analyzed for the presence or absence of a component or analyte. Sensor elements can also be used in the production of certain chemicals, such as in the dye industry, to obtain a measurement during the production process of a product's desired color, desired content, or other chemical properties.

[0091] Advantageously, according to some embodiments, the sensor element or a blood analysis system including such a sensor element further comprises a processor configured to compare the signal generated by the detector with a predetermined calibration reference to generate a quantitative measurement of the analyte level in the fluid. Furthermore, advantageously, according to some embodiments, the calibration reference is obtained using a dye-based calibration solution, such as an aqueous solution containing a tartrazine dye. Preferably, the dye-based aqueous solution is prepared from a typical rinse solution to which a calibration dye, such as tartrazine, is added. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings, in which:

[0093] Figure 1 is a schematic diagram of a liquid sample analyzer including a sensor assembly according to an embodiment of the present invention;

[0094] Figure 2 Schematically shown is a cross-sectional detail of a sensor assembly according to an embodiment. DETAILED DESCRIPTION

[0095] Reference below Figure 1 and Figure 2 , embodiments of the sensor assembly are described in conjunction with their operation in a liquid sample analyzer.

[0096] Figure 1 Schematically shows a liquid sample analyzer 1, which has an analyzer part, which has a signal processor 8, one or more analyte sensors 3 (ai), 4, a sample chamber 2 and a fluid processing infrastructure 20. In order to perform measurement, the user can provide a liquid sample at the input port 12a / b of the analyzer 1. The liquid sample is transferred to the first sample space 2a of the sample chamber 2 through the inlet port 6, and the first sample space 2a includes multiple analyte sensors 3, 4. As mentioned above, the analyte sensors 3, 4 are arranged to provide the basic simultaneous measurement of the analyte parameters in the complex liquid sample (such as a whole blood sample). Preferably, the sample size required for obtaining accurate and reliable data is as small as possible. For example, a detailed example of a sensor assembly design can be found in EP2147307B1, which is particularly suitable for measuring a plurality of different parameters in body fluids, particularly whole blood, and its use in a blood analyzer. The difference between this embodiment and this known assembly is that a porous membrane sensor element 100 is added, and here the porous membrane sensor element 100 is arranged at the downstream end of the sample chamber 2. Measurements are performed using analyte sensors 3 and 4, following preprogrammed instructions loaded into signal processor 8 and / or user input. Analyte sensors 3 and 4 generate signals representing physical parameters of the corresponding analytes and provide these signals to signal processor 8 in the analyzer portion. Signal processor 8 is adapted to receive and process the signals from analyte sensors 3 and 4 and provide the processed signals as output to the user or for subsequent / further data analysis. After the measurement, the liquid sample is drained, and the sample chamber is prepared for the next measurement.

[0097] Figure 1The embodiment of the analyzer shown is particularly suitable for measuring blood parameters and also includes an optional oxygenation measurement device 9 downstream of the sensor assembly. Therefore, performing measurements, calibration tasks and quality control procedures typically involves loading, unloading, flushing, cleaning and reloading of different liquids, which can be accomplished by a fluid handling infrastructure 20. Fluid handling can be controlled in an automated manner by a signal processor 8 based on pre-programmed instructions and / or user input. The fluid handling infrastructure 20 includes a plurality of reservoirs 21 pre-filled with processing liquids (RINSE / CAL1, CAL2, QC1, QC2, QC3) for flushing / washout, calibration and quality control tasks. The processing liquids (RINSE / CAL1, CAL2, QC1, QC2, QC3) have a known composition. The exact composition of a given batch can be stored in a chip 25, which can be attached to a box including the reservoirs 21, where the chip 25 can be read by the signal processor 8. The process liquid (RINSE / CAL1, CAL2, QC1, QC2, QC3) for a given process step can be selected by a fluid selection valve 22 and delivered to the sample chamber via the inlet port 6 via the supply line 12c. The correct filling of the sample chamber can be monitored and verified by visual inspection or by observing the propagation of the liquid interface through the system with the help of liquid sensors 10a, 10b, 10c located upstream and downstream of the sample chamber 2, for example, at the inlet 6 ("LS Inlet" 10a), the outlet 7 ("LS BG" 10b), and just after the oxygenation measurement device 9 ("LS OXI" 10c), respectively, according to known procedures. The fluid flow through the analyzer is driven by a pump 23, here a peristaltic hose pump, which is arranged downstream of the sample chamber 2 and the oxygenation measurement device 9 and is connected thereto via a fluid line 13. The discharged fluid is ultimately conveyed to a waste container 24 via a fluid line 14.

[0098] At startup, and in an ongoing manner, during normal operating hours, the analyzer 1 executes a self-control routine. If any anomaly is detected, the analyzer 1 indicates the deviation to the user and may further indicate a method for overcoming the error state. On the other hand, when the analyzer indicates normal operation, measurements can be taken immediately. Advantageously, according to some embodiments, the self-control routine can be executed during idle time, i.e. when the analyzer is in an idle state, when it is not used to perform actual measurements on user samples. The self-control routine may comprise continuously repeated measurements of a calibration grade process liquid having a precisely known composition, such as measurements stored on the chip 25. The signal obtained for each different analyte sensor 3, 4 at the well-known composition can then be used to continuously update the reference for the individual analyte measurements.

[0099] The second sample space 2b having a porous membrane sensor element 110 is integrated in the downstream part of the sample chamber 2, between the first sample space 2a and the outlet 7. The second sample space 2b is connected to the first sample space 2a via a short supply channel 102 comprising a flow disturbance element 104 as an abrupt change in the direction of the sample chamber 2 geometry.

[0100] Figure 2 A cross-sectional detail of a sample chamber 2 for accommodating a complex fluid sample is shown, the sample chamber 2 being defined by chamber walls and having an inlet 6 and an outlet 7, which define a flow direction from the inlet 6 toward the outlet 7 for fluid processing in the sample chamber 2. The sample chamber 2 comprises a first sample space 2a and a second sample space 2b connected by a supply channel 102, which comprises a flow-disturbing element 104. Thus, the flow-disturbing element 104 is arranged upstream of the second sample space 2b, between the first sample space 2a and the second sample space 2b.

[0101] The second sample space 2b includes a porous membrane sensor element 110 for detecting analytes. The porous membrane sensor element 110 has a porous membrane, wherein the front side defines a sensor surface for contacting the fluid sample. The sensor surface faces the second sample space 2b, and the porous membrane includes pores extending from corresponding openings in the sensor surface into the porous membrane. The pores are configured to communicate with the second sample space 2b via a diffusion fluid with respect to the analyte. In the embodiment schematically shown here, the sensor assembly is configured to detect multiple analytes in a whole blood sample, wherein the porous membrane sensor element 110 in the second sample space 2b is configured to detect high molecular weight analytes, more specifically, hemoglobin as a measure of hemolysis.

[0102] The first sample space 2a includes a plurality of additional sensor elements for detecting corresponding additional analytes, such as those mentioned above. The first sample space 2a is configured to maintain a laminar flow state during typical fluid processing operations. As seen in a section perpendicular to the main direction from the inlet 6 to the outlet 7, the first sample space 2a has a rectangular cross-section, wherein typical dimensions of the channel geometry defining the first sample space 2a are a width between 2 mm and 4 mm, for example 2.4 mm, and a height between 0.3 mm and 0.5 mm, for example 0.4 mm.

[0103] The flow-disrupting element 104 is formed as an abrupt change in the geometry of the sample chamber 2. Specifically, the flow-disrupting element is formed as a connecting nozzle that connects the supply channel 102 of the second sample space 2b to the downstream end of the first sample space 2a, substantially perpendicular to the main direction of the channel forming the first sample space 2a. The abrupt change in channel direction at the mouth of the supply channel 102 generates a flow disturbance within the supply channel 102. During fluid processing, when the sample chamber is filled in preparation for a measurement, this localized flow disturbance ensures that the fluid sample mixes with itself immediately before entering the second sample space 2b. Measured from the mouth of the supply channel 102 at the downstream end of the first sample space 2a to the entry orifice of the second sample space 2b, the supply channel 102 has a length of approximately 2 mm. This allows for a "well-stirred" complex fluid sample to be immediately prepared in the second sample space 2b.

[0104] Example

[0105] By providing a flow perturbation element immediately upstream of the sample volume where the measurement is performed using a porous membrane sensor element, an improvement in the measurement quality of high molecular weight analytes in continuous sections of complex fluids can be achieved. This improvement can be quantified by evaluating the signal ratio (WB / P ratio) between hemolyzed whole blood and corresponding hemolyzed plasma samples. An ideal sensor configuration has a WB / P ratio close to 100%.

[0106] The improvements achieved are illustrated by the following comparative data from measurements of hemolyzed whole blood (HWB), performed at two different locations within the porous sensor element within the sample chamber. The data are summarized in two data sets presented below in Tables 1 and 2. Each data set contains measurements of three nominally identical whole blood samples with a cell-free hemoglobin concentration of 100 mg / dL (HWB100) and three corresponding hemolyzed plasma samples with a cell-free hemoglobin concentration of 100 mg / dL (HWB100-Plasma), where the whole blood samples had a hematocrit value of 45%. The porous membrane in contact with these samples was optically probed, with the signal for a given sample being determined as the difference in absorbance at wavelengths of 416 nm and 461 nm. The signal values presented in the table are expressed in arbitrary units, while the WP / P ratios thus determined for each porous membrane sensor element, averaged together, are expressed as percentages. By moving the porous sensor element from a first position within the first sample space to a second position in the second sample space integrated in the outlet portion of the sample chamber, an increase in the WB / P ratio from an average of 66.5% in the first position to an average of 89.4% in the second position was observed.

[0107] The first set of data seen in Table 1 shows data measured using porous membrane sensors PM3, PM4, PM5, PM6, PM8, and PM10, each of which is arranged at a first position within the first sample space of the corresponding sample chamber, approximately 15 mm downstream of the junction of the inlet and the first sample space.

[0108] Table 1

[0109]

[0110]

[0111] The second set of data seen in Table 2 shows measurement data from porous membrane sensors PM19, PM20, PM21, PM22, each of which is arranged in a second position within the second sample space of the respective sensor assembly, in a flow channel connecting the first sample space at right angles and approximately 2 mm downstream of the junction. The second position of the porous membrane sensor element corresponds to Figure 1 and 2 The position in the second sample space is schematically shown in FIG.

[0112] Table 2

[0113]

Claims

1. A sensor assembly for analyzing a complex fluid sample, the sensor assembly comprising: a sample chamber for receiving a complex fluid sample, the sample chamber being defined by a chamber wall and having an inlet and an outlet, the inlet and the outlet defining a flow direction from the inlet toward the outlet for fluid processing in the sample chamber; Wherein, the sample chamber includes a first sample space and a second sample space, The second sample space includes a porous membrane sensor element for detecting an analyte; the porous membrane sensor element comprising a porous membrane having a front side defining a sensor surface for contacting a fluid sample, the sensor surface facing the second sample space, the porous membrane comprising dead-end pores extending from corresponding openings at the sensor surface into the porous membrane, wherein the pores are configured for diffusive fluid communication with the second sample space with respect to the analyte, Wherein, the sample chamber further comprises: a flow disturbance element arranged upstream of the second sample space and between the first sample space and the second sample space, The flow disturbance element is formed as a connecting nozzle, which connects the supply channel of the second sample space to the downstream end of the first sample space.

2. The sensor assembly according to claim 1, wherein The porous membrane sensor element is configured for detecting high molecular weight analytes.

3. The sensor assembly according to claim 1, wherein The first sample space comprises one or more further sensor elements for detecting respective further analytes.

4. The sensor assembly according to claim 1, wherein The flow-disturbing element is formed as an abrupt change in the sample chamber geometry.

5. The sensor assembly according to claim 1, wherein The flow disturbance element is formed as a connecting nozzle and is arranged at a certain angle relative to the main axis of the sample channel forming the first sample space, wherein the angle is at least 30 degrees, at least 40 degrees, at least 50 degrees, at least 70 degrees or 90 degrees relative to the main axis.

6. The sensor assembly according to claim 1, wherein The flow disturbance element is located upstream of the second sample space at a distance of at least 0.3 mm, 0.5 mm, 1 mm and / or at most 3 mm, at most 5 mm or at most 10 mm from the entry orifice of the second sample space.

7. The sensor assembly according to claim 1, wherein The sensor surface is planar.

8. The sensor assembly according to claim 1, wherein The sensor surface is arranged parallel to the flow direction from the inlet to the outlet for fluid processing in a second sample space of the sample chamber.

9. The sensor assembly according to claim 1, wherein: The second sample space has a cylindrical shape defined by a top wall, a bottom wall opposite to the top wall, and a peripheral wall connecting the top wall and the bottom wall; wherein the supply orifice is arranged at an upstream end of the second sample space; wherein a discharge orifice is arranged at a downstream end of the second sample space; and wherein the porous membrane sensor element is arranged in the top wall of the second sample space.

10. The sensor assembly according to claim 9, wherein The supply orifice and the discharge orifice are arranged opposite to each other in the peripheral wall.

11. The sensor assembly according to claim 9, wherein Viewed from the top wall to the bottom wall, the height of the second sample space is less than half, or less than one third, or less than one fifth, or even less than one tenth of the lateral dimension of the second sample space.

12. The sensor assembly according to claim 9, wherein The bottom wall is curved to reduce a distance between the bottom wall and the top wall in a central portion of the second sample space compared to a peripheral portion of the second sample space.

13. The sensor assembly of claim 1, wherein: The porous membrane sensor element is configured to detect the analyte by optical detection.

14. The sensor assembly of claim 1, wherein: The porous membrane is a translucent membrane.

15. The sensor assembly of claim 14, wherein: The porous membrane sensor further includes a reflective layer disposed on a front side of the semitransparent membrane.

16. The sensor assembly of claim 13, wherein: The porous membrane is a translucent membrane, wherein the porous membrane sensor further comprises: an optical input port connected to a rear side of the translucent membrane, the rear side facing away from the front side, the optical input port being adapted to supply detection light to a detection area of the translucent membrane through the rear side; and A light output port is connected to the back side of the translucent film, the light output port being adapted to collect an optical response from the translucent film through the back side.

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