WO2008020364A2

WO2008020364A2 - Biochemical sensor device

Info

Publication number: WO2008020364A2
Application number: PCT/IB2007/053116
Authority: WO
Inventors: Mark Thomas Johnson; Hendrik Roelof Stapert; Murray Fulton Gillies; Marc Wilhelmus Gijsbert Ponjee; Franciscus Petrus Widdershoven
Original assignee: Koninklijke Philips Electronics N. V.
Priority date: 2006-08-14
Filing date: 2007-08-07
Publication date: 2008-02-21
Also published as: WO2008020364A3

Abstract

The present application relates to a biological sensor device comprising a biological sensing element and an electrode arrangement, the electrode arrangement comprising an electrode (101) and an electrode structure (103, 105, 107, 109), the electrode structure (103, 105, 107, 109) being arranged around the biological sensing element (201) and around the electrode (101). In array form, the device is used for carrying out high throughput biospecific binding assays, hybridization assays etc. Since the electrode structure allows electrophoretic or dielectrophoretic concentration of the target molecules at the sensing element, thereby overcoming diffusion limited binding kinetics.

Description

Biochemical sensor device

FIELD OF THE INVENTION

The present invention is directed to the field of devices for the detection of one or more target particles in a fluid sample, especially to the field of devices for the detection of bio -molecules in an aqueous solution. BACKGROUND OF THE INVENTION

In order to sense target molecules of interest, the fluid to be analyzed is provided on a substrate material which contains capture sites for the target molecules which are subject of the detection. Such a capture site may be a corresponding DNA- strand if the target molecule is a DNA-Strand or an antibody in the case of a protein assay. The target molecules in the fluid will then bind to the capture site and remain there even after the fluid is removed. The target molecule contains a label enabling its detection or sensing.

In this context, the ability to control fluids on a biochip is essential. Besides general flow management which is required to transport bio-materials, the ability to control fluid convection locally offers options to enhance dissolution of reagents, to enhance mixing of (bio)chemicals and to enhance temperature uniformity. Specifically, in most bio-sensors (biological sensors) target molecules (e.g. DNA or proteins) are immobilized on biochemical surfaces using capturing molecules. The binding kinetics of the target molecules to the biochemical surface determine the speed and specificity of the bio-sensor. For low concentrations (pMol/L) of large bio-molecules, the binding kinetics will become diffusion-limited which results in an unacceptably long detection period. This is particularly the case for e.g. optical bio-sensors, electrical bio-sensors or single molecule electrical bio-sensors, since the target molecules must find the correct part of the surface where the associated capture molecules are situated. Present solutions to this problem as disclosed in US6,635,493,

US6,864,102 and US6,635,493 are based upon mechanical pumping of fluid through a porous membrane-type bio-sensor. The fluid is pumped several times through a membrane containing the capture molecules via a micro-fluidic system. The disadvantages of such systems are the relatively low lateral mixing efficiency per cycle, the relatively large dead volume, the relatively small effective area (=A_spot/A_tot) and the relatively large amount of analyte (100-500 μL) fluid that is required. Moreover, the fluid that flows through a spot is in the order of a few nano liters and number of molecules present in the volume typically is between 10² to 10⁹ molecules, wherein typically 10⁴-10⁵ capture ligands per μm² are used. Thus, the solution can become depleted quickly. Moreover, only a flow perpendicular to a membrane is possible and no lateral flow occurs. Therefore, the molecules of the analyte which are pumped through the wrong spot are useless. Further solutions as disclosed in US2005/0009004 and US 2005/0155863 are e.g. based upon electrically manipulating target particles. However, these solutions are not efficient, since a purposeful concentration of target particles at associated capture sites is not possible.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a concept for efficiently sensing target particles.

This object is achieved by the features of the independent claims.

The present invention is based on the finding that the sensing efficiency can be increased when employing an electric field for purposively concentrating target molecules at corresponding capture sites.

When exposing target particles in a fluid to an electric field, the target particles may move according to the electrophoretic principle, according to the di- electrophoretic principle or according to the electro-osmosis principle. In electrophoretic systems, charged particles move directly under the influence of DC fields. In di- electrophoretic systems, un-charged (polarizable) particles move directly under the influence of AC fields. In electro-osmosis systems, the particles move indirectly under the influence of fluid motion set up by the motion of ionic species in the liquid when electric fields are present.

The present invention provides a biochemical sensor device and specifically a biological sensor device comprising a biological sensing element for sensing target particles (e.g. target molecules) of interest. The biological sensing element may be e.g. a biological capture particle (e.g. a biological target molecule) being capable of capturing a corresponding target particle or molecule. As will be appreciated by those in the art, the target particle(s) and the capture particle(s) may be, but not limited to, the product(s) of an amplification reaction, including both target and signal amplification); purified samples, such as purified genomic DNA, RNA, proteins, etc.; raw samples (bacteria, virus, genomic DNA, etc.); biological molecular compounds such as, but not limited to, nucleic acids and related compounds (e.g. DNAs, RNAs, oligonucleotides or analogs thereof, PCR products, genomic DNA, bacterial artificial chromosomes, plasmids and the like), proteins and related compounds (e.g. polypeptides, peptides, monoclonal or polyclonal antibodies, soluble or bound receptors, transcription factors, and the like), antigens, ligands, haptens, carbohydrates and related compounds (e.g. polysaccharides, oligosaccharides and the like), cellular fragments such as membrane fragments, cellular organelles, intact cells, bacteria, viruses, protozoa, and the like. According to another aspect, the biological sensing element may be an optical target spot.

The biological sensor device may further comprise an electrode arrangement for generating an electric field which may concentrate a target particle towards the biological sensing element. Thus, the electrode arrangement and biological sensing element form a bio-sensor or a bio-sensor element. The electrode arrangement comprises an electrode (e.g. a single electrode) and an electrode structure which is arranged around the electrode and the biological sensing element. According to an aspect, the electrode arrangement surrounds or encloses the electrode and the biological sensing element. For example, the electrode and the biological sensing element may be arranged within a certain area on a surface of a substrate or within a certain area within the substrate. The electrode arrangement may surround or enclose the certain area being e.g. determined by the dimension of the electrode. According to an aspect, the biological sensing element is arranged on a surface of the electrode. For example, the surface is a top surface or a bottom surface or a side surface of the electrode. Furthermore, the biological sensing element may be arranged in a vicinity of the electrode. According to another aspect, the electrode arrangement may comprise a first electrode structure and a second electrode structure, the first electrode structure and the second electrode structure being arranged to enclose the biological sensing element. For example, the first electrode structure and the second electrode structure may be formed to generate an electric field concentrating a target particle towards the biological sensing element. In this case, a central electrode may be omitted. The biological sensing element and/or the electrode arrangement may be arranged directly either on a surface of a substrate or within the substrate.

According to an aspect, the electrode and/or the electrode structure and/or the biological sensing element may be arranged on a surface of a substrate comprised by the biological sensing device. Furthermore, the electrode and/or the electrode structure and/or the biological sensing element may be arranged within the substrate or at least partly within the substrate. In this case, the substrate may be porous with respect to the target particles.

According to an aspect, the biological sensing element is formed to sense or to capture a biological target particle of interest which is exposed to an electric field generated by the electrode arrangement in order to move or to concentrate the biological target particle towards the electrode or towards the biological sensing element. In order to generate the electric field, the biological sensing device may be configured to activate the electrode arrangement by applying a potential to the electrode and/or by applying a further potential to the electrode structure or to a part thereof in order to create a potential difference between the electrode and the electrode structure.

According to an aspect, the biological sensing device may comprise a means for activating the electrode arrangement, the means for activating being configured to generate the potential difference between the electrode and the electrode structure or between the first and the second electrode structure. For example, the means for activating is configured to apply a voltage signal to the electrode and to apply a further voltage signal to the electrode structure in order to create the potential difference. The means for activating may comprise a signal generator for generating the potentials or signals which are to be applied to the electrode and/or to the electrode structure. The electrode arrangement may comprise a plurality of electrode elements being arranged around the biological sensing element and/or around the electrode. The electrode elements may further be arranged to form a quadrupole or an octopole.

According to an aspect, the means of activating may be configured to apply different potentials to the electrode elements according to a certain activation scheme. For example, the means for activating may be configured to successively apply a potential to each electrode element while e.g. keeping the electrode being surrounded by the electrode elements at a certain potential, for example at a negative or at a positive potential. Furthermore, the electrode structure may form a continues ring surrounding the electrode and the biological sensing element. In addition, the electrode structure may comprise a plurality of concentric rings arranged around the biological sensing element and/or around the electrode, wherein the means for activating may separately apply a potential or different potentials to each of the concentric rings and/or to the electrode for generating an electric field pattern moving the targets particles towards the sensing element. According to an aspect, the plurality of electrode elements may be arranged to form a spiral comprising interleaved metal lines, wherein the biological sensing element and/or the electrode are arranged in the center of the spiral, wherein the means for activating may be configured to separately apply a potential or different potentials to the interleaved metal lines. The biological sensor device may comprise a plurality of electrode arrangements being arranged to form an array, each electrode arrangement comprising an electrode structure, wherein each electrode structure may surround an electrode and/or a biological sensing element. The electrode structures may be arranged to form continues potential rails, a potential rail forming either a column or a row of a matrix. According to an aspect, the first electrode structure(s) may be formed by first parallel potential rails and the second electrode structure(s) may be formed by second parallel potential rails crossing the first potential rails. Therefore, a potential rail may be a shared electrode for a plurality of electrode arrangements. Moreover, a respective electrode and a respective biological sensing element may form a matrix "entity" being enclosed by corresponding sections of the potential rails. According to an aspect, the electrode arrangements being arranged to form the array or being arranged to form columns and rows of a matrix are separately activatable. For example, the means for activating may be configured to create a potential difference between an electrode structure and an electrode which is surrounded by the electrode structure in order to activate a respective electrode arrangement in the array of electrode arrangements. Preferably, the means for activating is configured to activate a number of electrode arrangements in accordance with a predetermined activation pattern. The activation pattern determines the electrode arrangements in the array which have to be activated in order to generate e.g. a certain electric field. For example, the activation pattern determines a first number of electrode arrangements to be activated at a first time instant and a second number of electrode arrangements to be activated as a second time instant. Thus, at the given time instant only certain electrode arrangements associated with e.g. certain biological capture molecules are activated. Furthermore, the means of activating may be configured to activate different rows or columns of the array (or matrix) at different time instants to generate travelling electric fields.

The electrode structures comprised by the electrode arrangements may form spirals comprising interleaved metal lines forming electrode arrangements. The respective interleaved metal lines associated with an electrode structure may be electrically connected to further, corresponding interleaved metal lines associated with a further electrode structure, wherein the electrode structures may be identical. Thus, an interleaved metal line of electrode structure may be electrically connected to an interleaved metal line of another electrode structure being e.g. arranged next to the electrode structure in the row or in the column of the matrix or both. The rows or columns may by separately activatable by e.g. the means for activating. In order to sense different kinds of target particles using the same array, different biological sensing elements being formed to sense or to capture different biological target particles may be used. For example, a first number of electrode arrangements may be arranged around first biological capture molecules being formed to sense a first kind of biological target molecule and a second number of electrode arrangements may be arranged around second biological capture molecules sensing a second kind of biological target molecules.

According to another aspect, the liquid (e.g. a solution) in which biological target particles of interest are present may additionally comprise salt ions.

The biological sensor device may further be used in one or more of the following applications: bio-sensors used for molecular diagnostics; rapid and sensitive detection of proteins and nucleic acids in complex biological mixtures such as e.g. blood or saliva; high throughput screening devices for chemistry, pharmaceuticals or molecular biology; testing devices e.g. for DNA or proteins e.g. in criminology, for on-site testing (in a hospital), for diagnostics in centralized laboratories or in scientific research; tools for DNA or protein diagnostics for cardiology, infectious disease and oncology, food, and environmental diagnostics; tools for combinatorial chemistry; or analysis devices.

The present invention further provides a biological sensing system for molecular diagnostics or for rapid and sensitive detection of proteins and nucleic acids in complex biological mixtures such as e.g. blood or saliva or for high throughput screening for chemistry, pharmaceuticals or for molecular biology or testing e.g. for DNA or proteins e.g. in criminology, for on-site testing (in a hospital) or for diagnostics in centralized laboratories or in scientific research or for DNA or protein diagnostics for cardiology, infectious disease and oncology, food, and environmental diagnostics or for combinatorial chemical approaches, the biological sensing system comprising the biological sensing device according to the present invention. The biological sensing system may further comprise a detector for detecting the target molecules being e.g. captured by respective capture molecules. According to the invention, electrical manipulation of target bio- molecules is performed, which is essential for future generations of biochips, where e.g. reduced concentrations of bio-markers are to be measured. Electrical manipulation and local fluid control offer the ability to influence the binding kinetics of molecules to e.g. a surface and increases the speed of measurement. Moreover, the electrical manipulation can be used to 'electrically filter' certain bio-molecules from a solution. In addition, a specificity of the binding is improved by 'pulling' the target molecules from the surface in a controlled way (stringency test) by specifically removing the weakly bound (a- specifϊcally adsorbed) molecules. The inventive concept improves mixing and flow of an analyte and which results in a maximum exploitation of the analyte. Consequently, the required hybridization volume and time are reduced. Furthermore, the present concept increases the sensitivity, specificity and speed of operation of an optical or electrical biosensor by incorporating an integrated electrical pumping mechanism into the sensor device. The electrical pumping mechanism may e.g. be formed by the electrode arrangement and, optionally, by the electrode being surrounded by the electrode arrangement. Preferably, the bio-sensor comprising the electrode arrangement and the biological sensing element is arranged to form an array, wherein the pumping mechanism is configured to manipulate target particles in both a direction across the bio-sensor and in a direction perpendicular to the sensing surface without net movement of the fluid. For example, the bio-sensor array with integrated pumping mechanism may be realized using a large area electronics technology (which also is employed for manufacturing active matrix, e.g. TFTs or LCDs) such as low temperature poly silicon (LTPS), amorphous Si, diode, MIM (metal-insulator-metal) etc. Furthermore, the bio-sensor may be realized in the CMOS-based technology. Preferably, the driving of such an array of bio-sensors with integrated pumping mechanisms is realized using e.g. active matrix or CMOS-based driving principles. BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the present invention are described with reference to the following figures, in which: Fig. 1 shows a biological sensing device according to an aspect;

Figs. 2a, 2b show biological sensing device according to another aspect;

Figs. 3a, 3b show biological sensing devices according to another aspect;

Fig. 4 demonstrates a concentration of target particles exposed to an electric field across a surface of a substrate;

Fig. 5 demonstrates a concentration of target particles exposed to an electric field within a substrate; Fig. 6 demonstrates a concentration of target particles exposed to an electric field comprising a perpendicular field component;

Fig. 7 shows a biological sensing device according to another aspect;

Fig. 8 shows voltage signals used by the biological sensing device of Fig. 7 to generate electric fields; and

Fig. 9 shows a concentration of target particles exposed to an electric field.

DETAILED DESCRIPTION OF THE INVENTION

Before the invention is described in detail, it is to be understood that this invention is not limited to the particular component parts of the devices described or process steps of the methods described as such devices and methods may vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an" and "the" include singular and/or plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a fluid" may includes mixtures, reference to "a heat device" includes two or more such devices, reference to "a micro channel" includes more than one of such channels, and the like.

To provide a comprehensive disclosure without unduly lengthening the specification, the applicant hereby incorporates by reference each of the patents and patent applications referenced above.

The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents/applications incorporated by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed.

Fig. 1 shows a biological sensing device (bio-sensor element) comprising electrodes to create an electric field for concentrating target molecules at a sensor electrode. The biological sensing device comprises a (sensor) electrode 101 and an electrode arrangement with electrode elements (concentration electrodes) 103, 105, 107, 109 being arranged around the electrode 101. A means for activating (not shown in Fig. 1) may separately apply a potential or different potentials to each of the electrode elements 103 to 109. The electrode arrangement and the distinct electrode elements 103, 105, 107 and 109 may further be arranged on a surface of a substrate. According to an aspect, the means for activating may be configured to apply a further potential to the electrode 101, the further potential having e.g. a sign which is opposite to the sign of the potential(s) applied to the electrode elements 103 to 109. According to an aspect, a capture bio-molecule may be arranged on the electrode 101, wherein the device may be arranged within a substrate area 110.

The electrodes 103 to 109 are distributed laterally so as to provide electrical fields with at least a component in the plane parallel to the surface of the biosensor element. The electric field is used to create an additional movement of the target molecules relative to the capture electrodes of the element. The electrodes 103, 105, 107, 109 and/or 101 shown in Fig. 1 may be used to induce a (continuous) motion of molecules in the plane of the bio-sensor element and across the surface. The motion is set up to concentrate any target molecules within the (larger) electrode area towards the capture electrode 101, thereby increasing the possibility of capturing the target molecules. This is particularly important if capturing of a single target molecule is to be performed. A particularly suitable electrode structure for concentrating particles is a quadrupole structure which concentrates particles at the centre of the quadrupole electrodes. Furthermore, it is possible to use designs with more poles (i.e. octopoles etc.) as this may result in an even stronger field.

Fig. 2a shows a biological sensing device (bio-sensor array) comprising a plurality of electrodes (central electrodes and/or electrode arrangements) for creating an electric field for moving target molecules across the sensor. The biological sensing device comprises a plurality of biological sensing elements 201 being arranged to form rows and columns of an array. Each of the biological sensing elements is arranged on a corresponding electrode 203. The array of biological sensing elements 201 and the array of electrodes 203 are arranged on a substrate 205, e.g. on a surface of the substrate 205. Fig. 2b shows a side view of the biological sensing device shown in Fig. 2a, which may further comprise an element 207. According to an aspect, the element 207 may form a housing, e.g. a glass plate. According to another aspect, the element 207 may form a further substrate 207 covering the biological sensing elements 201 and the electrodes 203. For example, the further substrate 207 is porous with respect to target molecules of interest. The further substrate may e.g. be a hydro-gel.

Fig. 3 a shows a biological sensing device comprising a plurality of biological sensing elements 201 and an electrode arrangement comprising a plurality of lateral, e.g. continuous potential rails 301 and a plurality of e.g. continuous lateral potential rails 303 crossing the potential rails 301. The potential rails 301 may form a first electrode structure and the potential rails of 303 may form a second electrode structure. A means for activating the electrode arrangement may be configured to apply different potentials to the first and second electrode structure 301, 303, in order to generate a potential difference between the electrode structures 301, 303, so that an electric field concentrating target particles of interest towards a respective sensing element 201 is created. The biological sensing elements 201 may directly be arranged on the substrate 205. According to another aspect, each sensing element 201 may be arranged on a surface or in the vicinity of a corresponding central electrode. Fig. 3b shows a side view of the device shown in Fig. 3a.

Figs. 2a, 2b, 3a and 3b show bio-sensor arrays with an in-plane electrode array and bio-sensor arrays arranged on or at least partly within a substrate, a bio-sensor array may be designed such that a multiplicity of sensing elements, e.g. capture molecules, are arranged to form an array. The capture molecules are designed to immobilize corresponding target molecules from e.g. a fluid sample. The target molecules can subsequently be detected optically or electrically. The bio-sensor array may be positioned on the surface of a non-porous substrate or may be incorporated into a porous substrate. In the latter case, the porous substrate preferably allows for a movement of molecules in all directions.

The inventive bio-sensor array may comprise a multiplicity of electrodes or electrode structures which are distributed either laterally so as to provide electrical fields with at least a component in the plane parallel to the surface of the bio-sensor array or even directly below the bio-sensing element (203) to e.g. directly attract charged particles to the bio-sensing element as shown in Figs. 2a, 2b, 3a and 3b. The electrodes may be positioned next to the bio-sensing element (303) or underneath the bio-sensing element (203), or next and underneath the element (203, 303). The electric field is used to create an additional movement of the target molecules relative to the capture positions on the array. The additional electrodes forming e.g. the electrode structures may be realized using e.g. large area electronics or CMOS-based technology.

Fig. 4 shows a bio-sensor array comprising electrodes to create an electric field for moving target molecules across (e.g. on a top surface of a substrate) the sensor. In Fig. 4, a concentration of biological target particles exposed to lateral electric fields having field components depicted by the arrows towards biological sensing elements 201 is illustrated. The electric fields may be generated using e.g. the electrode arrangement shown in Fig. 3b.

Fig. 5 shows a biological sensing device forming a bio-sensor array comprising further electrodes to create an electric field for moving target molecules across and perpendicular to the sensor. The biological sensing device comprises e.g. a further electrode 501 extending above the biological sensing elements 201. The further electrode 501 is formed to generate a perpendicular field component depicted by the arrows. For example, a means for activating may apply a further potential to the further electrode 501 which may e.g. differ from the potential applied to the electrode structure 301 in order to generate a perpendicular field component or different perpendicular field components at different time instants.

Fig. 6 demonstrates a concentration of biological particles 601 within a substrate 603, which may be porous. Thus, the target molecules may even move through (bottom) the sensor. The biological sensing device shown in Fig. 6 comprises biological sensing elements 605 arranged within the substrate 603. The device further comprises an electrode arrangement 607 which is arranged on a surface of the substrate 603.

According to the embodiments shown e.g. in Figs. 4, 5 and 6, the electrode array may be used to induce e.g. a continuous motion of molecules in the plane of the bio-sensor. Motion of the molecules may be across the surface (for a non-porous substrate) or through the membrane (if porous) as e.g. shown in Fig. 6. The in-plane motion back and forth across the bio-sensor increases the capture possibility as all target molecules are repeatedly exposed to their relevant capture positions. This will speed up the sensing process and increase the sensitivity. Furthermore, the specificity can be increased by using the in-plane field to remove non bound molecules from the vicinity of the capture positions as well as non-specifically adsorbed molecules before optical/electrical analysis is carried out.

According to the embodiment shown in Fig. 5, the further electrode 501 or a further electrode array may be used to induce a motion of the molecules towards or away from the plane of the bio-sensor in addition to the (continuous) motion of molecules in the plane of the bio-sensor. The further electrode 501 or a further set of electrodes are provided on the bio-sensor to allow for a more defined perpendicular electric field. The additional motion of the molecules perpendicular to the surface can be used to further increase the capture possibility as the target particles (e.g. target molecules) are brought in more intimate contact with their respective capture molecules (i.e. by being forced towards the surface in the non-porous case). This will speed up the sensing process and increase sensitivity. Furthermore, the specificity can be increased by using the perpendicular field to remove non bound molecules from the vicinity of the capture positions before optical analysis is carried out (see e.g. steps 3 and 4 in Fig. 5). As e.g. shown in Figs. 2a to 6, the in-plane motion back and forth across the bio-sensor element will increase the possibility of capturing the target molecules as these may repeatedly be exposed to the capture electrode. This will speed up the sensing process and increase sensitivity. Furthermore, the specificity can be increased by using the in-plane field to remove non-bound molecules from the capture positions before electrical sensing is carried out.

The bio-sensing element (201) may further be arranged in the form of an array which the may furthermore comprise additional electrodes, as described with respect to the embodiments of Figs. 2a to 6, to further ensure that the target molecules are moved to the correct part of the array where the associated capture electrodes are situated. In this case, the sensing procedure may comprise the sequential steps of firstly moving molecules laterally across the array (in either a random or an electrically filtered manner) and secondly concentrating the molecules towards the capture electrodes in order to try to capture any target molecules, which happen to be within the bounds of the element. The bio-sensor array with integrated pumping mechanism is preferably realized using a large area electronics technology or alternatively using a CMOS-based technology. Preferably, the driving of such an array of bio-sensors with integrated pumps is realized using either active matrix or CMOS-based driving principles. Alternatively, the pump electrodes may be arranged as spirals with two or more interleaved metal lines. With a proper biasing scheme applied to the pump electrodes, a periodic electrostatic potential profile can be created above the electrodes that will trap e.g. positive ions in the potential maxima and e.g. negative ions in the potential minima. With a proper oscillating biasing scheme, the periodic potential profile can be spatially moved which creates an electrostatic traveling wave pattern. The forces acting on the ions are proportional to the electric field in the traveling wave pattern. The average ion velocity is proportional to a product of the average electric field and the ion mobility. This limits a transport velocity at a given average electric field strength related to the maximum achievable bias potentials. According to the invention, salt ions may be dragged in the liquid e.g. instead of the bio-molecules which increases the ion mobility. This approach may be used in all embodiments and has several advantages, since salt ions are always charged and are typically much more abundant then bio -molecules. Moreover, salt ions typically have much higher ion mobilities than bio -molecules which allows to move them much faster than bio -molecules. Because of the friction of the ions with the water, the ions will drag water molecules in the direction of their motion. As a result, a 3-D convective pattern, similar to the Rayleigh-Benard convection pattern, can be created above the spiral to transport bio -molecules.

In order to further increase the efficiency, an array of spirals, each with a detection electrode (or an optical target spot) in the middle can be used to create a regular pattern of 3-D convection flows. In this way, all target molecules present in the volume of the convection pattern are pumped over the central detection electrode, so that the target molecules only have to diffuse across a boundary layer instead of a total volume to reach the capture probes on the detection electrodes, since (because of the symmetry) the water velocity at the centre of the spiral will be zero and diffusive transport is needed for the last part towards the detection spots/electrodes. Such an array of spirals may be individually driven using the underlying CMOS electronics.

Fig. 7 shows a biological sensing device comprising an array of spiral pump electrodes and an interconnection architecture. The biological sensing device comprises a plurality of electrode arrangements forming rows and columns of an array. Each electrode arrangement comprises a plurality of interleaved metal lines being arranged to form a spiral and a plurality of central electrodes 700, each central electrode 700 being arranged in the center of a corresponding spiral. Each electrode arrangement may comprise a first metal line 701, a second metal line 703, a third metal line 705 and a fourth metal line 707. For example, the first metal lines 70 land the third metal lines 705 of adjacent electrode arrangements arranged in the same row may be electrically connected. Moreover, the second metal lines 703 and the forth metal lines 707 of adjacent electrode arrangements arranged in the same row may be electrically connected. The biological sensing device further comprises first terminals 709 connected to the second metal lines 703, second terminals 711 connected to the first metal lines 701 and third terminals 713 which may also be electrically connected to the third metal lines 705. The biological sensing device further comprises fourth terminals 715 electrically connected to the fourth metal lines 707. For connecting respective metal lines, shunts 717 may be used, wherein further connections to e.g. the means for activating or to further metal lines may be realized using via holes 719.

In order to create e.g. a different electric field pattern at different time instants, different potentials or different voltage signals may be applied to the terminals 709 to 715. According to an aspect, the different potentials or voltage signals may be applied at different time instants. According to another aspect, the different potentials or voltage signals may be phase-shifted with respect to each other. The potentials or voltage signals may be generated and applied to the terminals 709 to 715 by the means for activating. According to Fig. 7 showing a spiral array with four interleaved metal lines, all spirals may be driven by the same set of drive signals as shown in Fig. 8. By using an appropriate repetition scheme, all metal lines can be connected from the periphery. The structure of Fig. 7 may be manufactured using a plurality of metal layers which enable an efficient interconnection scheme. The metal lines may be connected with a second metal layer running below the metal layer on which the electrodes are arranged. Via holes may be used to connect the two metal layers and to shunt adjacent electrodes in such a way that they are effectively connected in odd and even columns and in odd and even rows. Furthermore, multiple parallel via holes may be used for better yield and lower contact resistance. The architecture of Fig. 7 is does not require long wires to be arranged in a lower metal level, since only the shortest possible shunts may be used. Consequently, the lower metal level is nearly completely available for routing of the detection electronics below the detection spots or the electrode 700. The electrode lines may further be covered with insulting layers to protect the metal form reactions with the liquid. However, it may also be possible to omit the insulating layer (e.g. if noble metals are used that do not react with the liquid, or if the voltages are low enough or the driving frequencies are high enough so that e.g. an electrolysis is effectively suppressed).

Another advantage of spiral arrays is that they occupy the dead surface array in e.g. single-molecule bio-sensors with small detection electrodes. The electrodes may be too small to be able to detect single molecules. However, the electronics below each electrode can occupy considerable larger area than allowed by the minimum metal pitch. Filling the dead area with pump electrodes can compensate the resulting reduction in active area. This may be even more beneficial than generating the highest possible density of detection electrodes. In an alternative embodiment, a second surface with a spiral array aligned to the bottom array can be placed above the liquid (as a top cover plate). By creating a traveling wave of opposite direction to that at the bottom, the arrays will collaborate. Alternatively, it is also possible to use a top spiral array only.

Fig. 8 shows an oscillating biasing scheme (voltage signals Vl, V2, V3, V4 over time) which may be used for operating the device shown in Fig. 7. The voltage signals Vl to V4 may be phase-shifted with respect to each other by the amount of 90°. With reference to Fig. 7, the first voltage signal Vl may be applied to the first terminal 709, the second voltage signal V2 may be applied to the second terminal 711, the third voltage signal V3 may be applied to the third terminal 713 and the fourth voltage signal V4 may be applied to the fourth terminal 715 which is also depicted in Fig. 7 by corresponding arrows.

With the 4-phase oscillating biasing scheme of Fig. 8, a traveling wave potential profile can be created that moves the target molecules towards the central detection spots or electrodes 700. However, a traveling wave running in an opposite direction would also create a 3-D convection pattern and transport bio-molecules from the bulk of the liquid along the detection spot or the electrode 700. This is an advantage when compared with directly dragging bio-molecules over the surface in which case reversing the direction of the traveling wave would result in a depletion of bio-molecules in the centres of the spirals. An opposite convection pattern may be even more advantageous because bio-molecules from the bulk reach the central spot first before they can attach parasitically to other parts of the surface area.

According to the invention, the electrode array or the array of electrode arrangements or the array of electrode structures may be used to 'electrically filter' bio- molecules e.g. on the basis of polarizability (e.g. a dielectrophoresis array with varying frequency), net charge (electrophoresis array) etc. within the solution and in this manner selectively move only those specific molecules towards a given capture position which are indeed capable of being captured there. This approach differs from the embodiments where essentially all molecules are moved in the same manner. The combination of filtering of the target molecules and the array of capture molecules further increases the sensitivity and the selectivity of the array as now far less target molecules of the wrong type will reach the capture areas. In this case, the ordering of the capture sites may preferably be chosen to give the maximum benefit of the electrical filtering afforded by the presence of the additional electrodes. Fig. 9 demonstrates a concentration of target particles using a quadrupole electrode using the dielectrophoretic effect (AC electric field at two frequencies: 500 kHz and 5 MHz).

Claims

CLAIMS:

1. A biological sensor device, comprising:

a biological sensing element (201); and

an electrode arrangement, the electrode arrangement comprising an electrode (101; 203; 700) and an electrode structure (103, 105, 107, 109, 301, 303), the electrode structure (103, 105, 107, 109; 301, 303) being arranged around the biological sensing element (201) and around the electrode (101; 203; 700).

2. The biological sensor device according to claim 1, the biological sensing element (201) comprising a biological capture particle.

3. The biological sensor device according to claim 1 or 2, further comprising a means for activating the electrode arrangement, the means for activating being configured to create a potential difference between the electrode (101; 203) and the electrode structure (103, 105, 107, 109; 301, 303) to activate the electrode arrangement.

4. The biological sensor device according to any one of the claims 1 to 3, the biological sensing element (201) being arranged on a surface of the electrode (101; 203; 700).

5. The biological sensor device according to any one of the claims 1 to 4, comprising an array of electrode arrangements, each electrode arrangement in the array of electrode arrangements comprising an electrode structure (103, 105, 107, 109; 301, 303) being arranged around an electrode (101; 203; 700) and around a biological sensing element (201).

6. The biological sensor device according to claim 4 or 5, further comprising a means for activating a number of electrode arrangements in accordance with a predetermined activation pattern, the means for activating being configured to create a potential difference between an electrode (101; 203; 700) and an electrode structure (103, 105, 107, 109; 301, 303) being arranged around the electrode (101; 203; 700) to activate a respective electrode arrangement.

7. The biological sensor device according to any one of the claims 4 to 6, each electrode structure forming a spiral comprising a number of interleaved metal lines (701, 703, 705, 707), an interleaved metal line of an electrode structure associated with an electrode arrangement being electrically connected to a further interleaved metal line of a further electrode structure associated with a further electrode arrangement.

8. A biological sensor device, comprising:

a biological sensing element (201); and

an electrode arrangement, the electrode arrangement comprising a first electrode structure (301) and a second electrode structure (303), the first electrode structure and the second electrode structure (301, 303) being arranged to surround the biological sensing element (201), the first electrode structure (301) and the second electrode structure (303) being formed to generate an electric field concentrating a target particle towards the biological sensing element (201).

9. The use of the biological sensor device according to any one of the claims 1 to 8 in one or more of the following applications:

biological sensors used for molecular diagnostics; rapid and sensitive detection of proteins and nucleic acids in complex biological mixtures such as e.g. blood or saliva; high throughput screening devices for chemistry, pharmaceuticals or molecular biology; testing devices e.g. for DNA or proteins e.g. in criminology, for on-site testing (in a hospital), for diagnostics in centralized laboratories or in scientific research; tools for DNA or protein diagnostics for cardiology, infectious disease and oncology, food, and environmental diagnostics; tools for combinatorial chemistry; and analysis devices.

10. A biological sensing system for molecular diagnostics or rapid and sensitive detection of proteins and nucleic acids in complex biological mixtures such as e.g. blood or saliva or high throughput screening for chemistry, pharmaceuticals or molecular biology or testing e.g. for DNA or proteins e.g. in criminology, for on-site testing (in a hospital), for diagnostics in centralized laboratories or in scientific research or DNA or protein diagnostics for cardiology, infectious disease and oncology, food, and environmental diagnostics or combinatorial chemical approaches, the biological sensing system comprising the biological sensing device according to anyone of the claims 1 to 8.