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WO1992021959A1 - Procede et appareil de detection electrochimique de substances biologiques - Google Patents

Procede et appareil de detection electrochimique de substances biologiques Download PDF

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Publication number
WO1992021959A1
WO1992021959A1 PCT/US1991/002448 US9102448W WO9221959A1 WO 1992021959 A1 WO1992021959 A1 WO 1992021959A1 US 9102448 W US9102448 W US 9102448W WO 9221959 A1 WO9221959 A1 WO 9221959A1
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WO
WIPO (PCT)
Prior art keywords
substrate
substance
enzyme
electrodes
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1991/002448
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English (en)
Inventor
Ricardo J. Moro
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DIAGNOSTIC CONCEPTS INTERNATIONAL Inc
Original Assignee
DIAGNOSTIC CONCEPTS INTERNATIONAL Inc
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Filing date
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Application filed by DIAGNOSTIC CONCEPTS INTERNATIONAL Inc filed Critical DIAGNOSTIC CONCEPTS INTERNATIONAL Inc
Publication of WO1992021959A1 publication Critical patent/WO1992021959A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/58—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving labelled substances
    • G01N33/581—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving labelled substances with enzyme label (including co-enzymes, co-factors, enzyme inhibitors or substrates)
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
    • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
    • G01N33/54366—Apparatus specially adapted for solid-phase testing
    • G01N33/54373—Apparatus specially adapted for solid-phase testing involving physiochemical end-point determination, e.g. wave-guides, FETS, gratings
    • G01N33/5438—Electrodes

Definitions

  • he present invention relates to a method and apparatus for the detection of organic substances, and more particularly relates to an improved ELISA reader for detecting trace amounts of biological substances in a sample.
  • ELISA Enzyme Linked Immuno Sorbent Assay
  • a second antibody specific to the same antigen is added and bonded thereto.
  • the second antibody has been covalently conjugated prior to its introduction with an enzyme which will react with a substrate to cause a color change therein given the right environmental conditions.
  • the degree of color change in the substrate is proportional to the amount of the biological substance such as an antigen sought to be detected.
  • ELISA readers that measure light absorption are several.
  • the readers themselves are delicate and sensitive and require constant adjustment to maintain optimal sensitivity.
  • the linear response of the readers falls within a very narrow range so that each test requires large numbers of dilutions so that at least one or two of such dilutions falls within the linear range of the instrument.
  • a relatively intense light source is required making it more difficult to obtain a portable unit having regard to the inherent power requirements of the system, and of course the plastic lens at the bottom of each well must pass the light without distortion, necessitating the use of relatively expensive optical grades of plastic which further adds to the costs.
  • the readers themselves are relatively expensive (prices range from $6,000. for relatively simple models, up to $28,000. for units with computerized data management and analytical capabilities) and some existing readers perform only one light measurement at a time, making the reading of a plate with ninety-six wells a relatively time-consuming process.
  • the present invention contemplates the use of enzyme conjugates which promote the formation of ions in the substrate, rather than color reactions.
  • One such conjugate uses urease which catalyzes the transformation of urea into ammonium carbonate.
  • the ammonium is present in the substrate in the form of ions which change the conductivity/resistivity of the substrate. This change can be measured and is directly proportional to the amount of biological material present in the substrate that is to be measured. Quantifying the change will produce a measurement of the biological substance useful to the tester.
  • a method of performing an enzyme-linked immuno sorbent assay of a biological substance in a substrate comprising utilizing an enzyme conjugate to react with the biological substance to cause the release of ions into the substrate, measuring the change in resistivity of the substrate due to the presence of the ions, generating an analog signal in response to the measurement of resistivity, converting the analog signal into a digital signal, and quantizing the digital signal and outputting the same in human-readable form for indicating the quantity of the biological substance present in the substrate.
  • an apparatus for performing an enzyme-linked immuno sorbent assay of a biological substance in a fluid substrate comprising means for measuring the resistivity of the substrate and producing an analog signal representative thereof, converter means for converting the analog signal into a digital signal, and processing means to process the digital signal to produce numerical data indicative of the quantity of the biological substance in the substrate.
  • Figure 1 is a bottom plan view of a two-pin electrical probe forming part of the proposed ELISA reader.
  • Figure 2 is a top plan view of the probe of Figure 1.
  • Figure 3 is a block circuit diagram of a computer- based ELISA reader in accordance with one aspect of the present invention.
  • Figure 4 is a schematic diagram of the ELISA reader card circuit for computer installation.
  • Figure 5 is a block circuit diagram for a portable/hand-held ELISA reader in accordance with another aspect of the present invention.
  • Figure 6 is a schematic diagram of the portable reader of Figure 5.
  • Figure 7 is a schematic diagram of a first part of a modified embodiment of an ELISA reader card circuit for use with a computer.
  • Figure 8 is a schematic diagram of the second part of a modified circuit for use with a computer.
  • Figure 9 is a partly schematic, bottom plan view of an electrode head with a matrix of electrodes thereon.
  • the basic ELISA test procedure described above for colormetric measurement is followed in the present instance with the exception that the enzyme conjugate used to induce color reactions (usually peroxidase antibody or alkaline phosphatase) is replaced with, for example, a urease conjugate for transforming urea into ammonium carbonate.
  • the presence of ammonium ions in the substrate raises its Ph, which can be detected using well known techniques, but this provides only a visual confirmation of the presence of the ions without a quantitative measurement of concentrations.
  • the other change in the substrate is, as aforesaid, to its resistivity/conductivity which can be measured in a quantitative sense.
  • an electrical probe 10 having ninety-six pairs of conductive pins or electrodes 11 corresponding to the ninety-six wells on the plastic plate (not shown) .
  • the pairs of pins 11 are arranged into twelve columns 1-12 and eight rows A-H, with the pins in each column being connected in parallel and thence to one of electrical contacts 14, as shown in Figure 2, and the pins of each row being similarly connected together and thence to an electrical contact 15, as shown in Figure 1.
  • the switching between pin pairs and data acquisition is computer-implemented.
  • the computer-based reader card is illustrated schematically with reference to Figures 3 and 4.
  • An IBM XT (Trademark of IBM Corporation) or compatible computer may be used for this purpose and the card may be plugged into one of the expansion slots therein for direct input of the data into the computer.
  • Probe 10 is placed in contact with the plastic well plate so that each of pin pairs 11 can measure the resistivity of the solution in its respective well, this resistivity being a function, as aforesaid, of the presence of ammonium carbonate ions released into solution as a result of the enzymatic reaction.
  • the computer itself is programmed to sample and analyze the data whereby each of the pairs of electrodes 11 is sequentially connected to an analog/digital converter through an electronic inverting switch which prevents polarization of the electrodes.
  • address decoder 20 comprising two 74138 and one 7402 integrated circuits, is activated.
  • timer 22 is activated to enable multiplexers 24 and 25, both of which are latched to the data on the input bus 26 by the IOW instruction.
  • the bus data determines the pair of pins 11 on probe 10 to be read with multiplexer 24 selecting one of columns 1 to 12, and multiplexer 25 selecting one of designated rows A to H.
  • Analog switch 32 connected to both of the multiplexers flips the polarity of pins 11 at a rate of approximately 700 Hz to prevent potentially deleterious sustained polarization of the electrodes.
  • Switch 32 is itself pulsed to flip the polarity of the electrodes by means of a square wave generator 34 which produces the 700 Hz signal required for this purpose.
  • the analog resistivity measurement taken by the pairs of pins determines the time period that the output of timer 22 is high. That is, the duration of the timer's output signal is determined by the resistivity of the solution in the measured well.
  • the output is connected to a three- state line driver 38 (a 74244 IC) which outputs a digital signal to bus 26.
  • the data on input bus 26 will be 00000001, which value is read in accordance with the computer program which activates the driver through an IOR command to allow the computer to read the number on bus 26. If the number on the bus is 1, the program remains in a loop which subtracts one unit to a preset variable.
  • variable's value when the number on the bus equals 0, the program exits and the variable's value will be directly proportional to the resistance of the substrate.
  • the presence of a relatively large number of ammonium ions will, of course, decrease the resistance of the substrate and will cause a small decrease in the variable's initial value.
  • a weak reaction will cause more loops to decrease the variable's initial value to produce a smaller final value.
  • the values so produced are outputted in some useful human-readable form or stored in memory for subsequent analysis.
  • measuring electrolyte conductance using a timer as configured in the present embodiment provides a very large dynamic range without the need to switch components (resistors) .
  • a very large resistance (low conductance) in the solution being tested keeps the timer 22 ON for a prolonged period of time, thus yielding a high count output.
  • a very small resistance (a very high conductance) in the solution still provides a measurable period of time during which the timer 22 is ON.
  • the dynamic range is thus only dependent on the speed and the maximal number of counts an associated counting device can achieve and current electronic technology allows several orders of magnitude more speed and counting capacity than necessary for electrolyte conductances measurements in accordance with the present invention.
  • the voltage applied to the electrodes is a few millivolts (typically 1-50 mV) . This makes signal amplification mandatory before any processing can be done (direct measurement with an instrument, digitalization, etc.). Should the resistance in the solution be high, then the amplification circuit can be represented as a high impedance input amplifier. A high input impedance makes any amplifier very prone to noise.
  • the spikes caused by the switching ON and OFF of the pulses may become a source of noise, depending on their amplitude and the amplifiers gain.
  • the voltage applied to the electrodes is the same as the power supply feeding the timer. This is normally 5 Volts. No amplification is required, thus the problem of noise interference is eliminated along with the complexity added by the amplifying circuit.
  • a suitable two-pin electrical probe (not shown) is immersed in the well to be measured, the probe being shaped to fit the well as required.
  • the measurement is initiated by closing a switch 54 referred to as a reading switch, which triggers logic gate unit 40 to deliver a LOW output signal to a timer 41 and HIGH signal to a predetermined number such as 9999.
  • Timer 41 is actuated by the LOW signal from gates 40 to deliver a HIGH signal of its own to downcounters 42 which begins to count down from 9999.
  • the same HIGH signal from timer 41 simultaneously disables display drivers 43 to burn LCD display 44 off during the reading period.
  • the timer's LOW signal deactivates the downcounters and reactivates drivers 43, and hence LCD 44, to display the values present at the outputs of downcounters 42.
  • the time interval that drivers 43 are disabled by timer 41 is related to the resistance of the sample being measured in the well, in which the electrodes of the probe are immersed, and the value of capacitor Cl.
  • downcounters 42 count down the pulses from an 8 KHz clock generator 46. If the reaction in the well is strong and a relatively large number of ions are released into solution, the resistivity of the substrate will be low and the signal from timer 41 will disable drivers 43 and enable downcounters 42 for a relatively short period of time. The number of downcounted pulses from clock generator 46 will be relatively few and, consequently, the number output on LCD 44 will be large.
  • timer 41 will disable drivers 43 and enable downcounters 42 for a proportionately longer period of time, with the result that a greater number of pulses from clock generator 46 will be downcounted to produce a lower numerical reading on LCD 44.
  • the response of the portable reader is linear so that the reading on LCD 44 will be directly proportional to the strength of the enzymatic reaction-producing ions which, of course, is a function of the relative concentration of the particular biological substance being tested for.
  • Clock generator 46 provides a further 60 Hz to drive the backplane of LCD 44.
  • the portable reader can be constructed to read the ninety-six wells of a standard plate one at a time or in multiples of up to and including all ninety-six wells.
  • FIG. 7 and 8 Illustrated in Figures 7 and 8 is a modified embodiment of a circuit 100 for use in the invention in the alternative to the circuit illustrated in Figure 3 and partly in Figure 4.
  • the circuit 100 is used in preference to the circuit of the earlier embodiment where there is likely to be a large variance in resistivity of analytes in various wells that could influence the resistance results from adjacent wells.
  • the principal difference between the circuit 100 and that shown in Figure 4 is that the present circuit 100 uses six 16 channel analog multiplexers 102 through 107, as compared to the pair of 8 and 16 channel multiplexers 25 and 24 respectively that are shown in Figure 4.
  • the multiplexers 102 through 107 are shown in Figure 8 and provide for ninety-six total channels corresponding with the ninety-six wells of a standard plate within which ninety-six analytes are placed for testing.
  • the circuit 100 is divided into first portion 106 which is mounted on a card for insertion into a conventional expansion slot in a personal computer and is illustrated in Figure 7.
  • a second portion 107 of the circuit 100 is mounted on a card and illustrated in Figure 8 along with portions from a piggyback card.
  • a bus 109 is mounted on the left hand side of the card and connected to a pair of decoders 110 and 111 operate together as a hexadecimal address decoder.
  • a decoder 113 decodes the directional flow of information from or to the computer.
  • the direction decoder 113 functions in conjunction with the address decoders 110 and 111 to determine the direction of information that is passed to it from the computer.
  • the output of this decoding process is used to direct a bidirectional bus driver 115 and a latch 117.
  • circuit lines which carry data from the bidirectional bus driver 115 and latch 117, as well as the decoding lines (write $14B, write $18B, read $14B and read $18B) and the input power lines, are connected to the remainder of the apparatus by a connector 120 through a suitable twenty-five line connector cable.
  • a connector 130 for connecting with the connector 120 shown in Figure 7.
  • the highest bit from the connector 120 (D7) is used by the circuit 100 to detect the status of the output of the address decoder 111.
  • the rest of the circuit lines from the connector 130 are grounded through resistors in order to produce a zero value.
  • the connector 130 is joined to the multiplexers 102 through 107 by circuit lines.
  • the latched lines (DLO through DL7) are used to select which multiplexer 102 through 107 respectively is enabled.
  • the enabled line is decoded by a decoder 132 in cooperation with the output of a timer 134 such that none of the multiplexers 102 through 107 are left on in between readings.
  • FIG. 9 Shown in Figure 9 is an electrode head 150 having ninety-six electrodes 151 and ninety-six companion electrodes 152 arranged in respective pairs and in a matrix adapted to be placed in a prearranged set of ninety-six solution-filled wells for testing.
  • a respective one of each of the multiplexers 102 through 107 connects to one of the ninety-six electrodes 151 through a circuit line identified as Probe 2 in Figure 8 and headers 155 and 156 shown in Figure 9.
  • Each of the electrodes 151 along with a respective companion electrode 152 is associated with sampling of a particular one of the ninety-six wells.
  • the companion electrodes 152 are tied together by a circuit line identified as Probe 1 in Figure 8.
  • the respective electrode 151 and its companion electrode 152 which are necessary to read the resistance in a particular likewise-numbered well are connected to the circuit lines Probe 1 and Probe 2.
  • the resistance generated through the selected well is utilized as the R component in the RC network that determines the length of the pulse of the timer.
  • a quad bilateral switch 137 in Figure 8 switches the polarity of the electrodes approximately five hundred to two thousand times per second.
  • the switching frequency is determined by timer 138 operating in an astable mode and flip-flop 139 acting to divide the frequency rate in half while assuring a perfectly square wave.
  • Headers 140 and 141 connect the multiplexers 102 through 107 to the respective electrodes. This is accomplished by piggybacking the circuit board containing the remainder of the circuit shown in Figure 8 with a second circuit board including headers 140 and 141 underneath.
  • the circuit 100 is controlled by a personal computer as has been described for the previous embodiment. Initially, a number between zero and ninety-five and representing the range of ninety-six possible and numbered testing wells is written to address $18B. This number is then latched by latch 117 which selects, in conjunction with decoder 132, which pair of electrodes 151 and 152 is associated with the respective selected well. Simultaneously, timer 134 is triggered which enables decoder 132. Data line D7, which is connected to the output of timer 134, goes HIGH. This information is passed by driver 115 to the bus 109 when a read $18B operation is done.
  • a loop in the computer program polls address $18B and a unit is added to an energy variable every turn of the loop while bit 7 on $18B is HIGH.
  • the adding loop is discontinued.
  • the time e ' lapsed and, therefore, the resistance or conductance of the solution is represented by the value of the variable in the loop.
  • the variable value is stored in an identified location in the computer memory which has available at least ninety-six positions for storing each reading of the ninety-six electrode pairs 151 and 152 and the resistance of the numbered wells associated therewith. These values are then processed for purpose of rendering the values human-readable and displayable as discussed for the previous embodiment.
  • the hand-held probe may be adapted to contain a multiplexing device for the selection of respective pin pairs, a processing unit to be used, for example, to generate an output of actual concentrations or other useful data, and even a miniature printer for output of the measured data on paper.
  • the apparatus of the present invention can be adapted for use with ELISA kits that were originally intended to be read photocolormetrically and which normally include conjugate enzymes such as alkaline phosphatase or horseradish peroxidase.
  • conjugate enzymes such as alkaline phosphatase or horseradish peroxidase.
  • Such kits are available for numerous analyses, but are not directly usable for the method of the present invention.
  • alkaline phosphatase and horseradish peroxidase kits may be adapted to function in conjunction with the apparatus and method of the present invention by either of two approaches.
  • a first approach involves the inclusion of an additional antibody reagent, such as urease-linked anti- horseradish peroxidase or urease-linked anti-alkaline phosphatase.
  • the analysis is then initiated in the manner of an ELISA color analysis, but the additional reagent linked to urease is added in an additional step prior to testing with the apparatus of the present invention.
  • a second approach involves replacing the monoclonal or polyclonal detection antibodies that are conventionally linked to current enzymes, such as the horseradish peroxidase with urease-linked antibodies. The analysis would then be conducted in accordance with the methods described above. While this approach is not as easily implemented as the first approach, since a urease conjugate must be developed for each test kit analyte, it has an advantage of requiring one fewer analytical steps as compared to the first approach.
  • the present invention will increase the availability of ELISA technology.
  • the apparatus of the present invention is relatively compact and very portable relative to conventional color-reading devices, the invention can be easily taken outside a laboratory to do field tests, such as on a space station (where reduced energy output is also important) or on a farm where a farmer can directly and quickly check a crop for a viral infection and take immediate corrective action.
  • the invention also increases the range and sensitivity of the tests available and, in this manner, substances such as acquired immune deficiency syndrome (AIDS) antibodies can be detected in blood relatively very soon after infection instead of after a longer delay period with the less sensitive color-reading devices.
  • AIDS acquired immune deficiency syndrome
  • the lower cost of the present invention as compared to color-reading devices also increases availability in third world countries and the like.
  • the apparatus of the present invention may be robotized, and all results computerized and automatically analyzed with a printout of such analysis, so as to provide a uniform and consistent pattern of analysis for each set of tests.
  • the conductive electrode probes may be constructed of flexible material, especially conductive plastic or rubber, to reduce the likelihood of an operator accidently pricking himself or herself with a probe used with an infectious material and to reduce mechanical problems.
  • the present method and apparatus are adapted to quantitatively measure immunological reactions other than those induced by enzymatic reactions but wherein, as a result of the reactions, ions are released into solution.
  • examples include the hybridization reaction between a natural nucleic acid and another natural or artificial nucleic acid, a hapten-antibody reaction or a biotin- avidin/streptavidin reaction.
  • the present invention may be used in combination with deoxyribonucleic acid (DNA) hybridization that can use DNA amplification to analyze for very small quantities of genes or DNA.
  • DNA deoxyribonucleic acid
  • a conductivity reader is provided with a robot arm to carry out and read the conductance of the reaction solution and a temperature controlling device that is made to cycle, as required by the Taq system utilizing Taq polymerase, by a dedicated computer.
  • a blood sample from a patient suspected of having AIDS is adequately prepared and incubated in a nitrocellulose-coated plate well.
  • the bottom of the well is coated with nitrocellulose in the present invention since the bottom is not required to be optically transparent as with conventional color readers.
  • the system can be used to test for HIV virus. If HIV nucleic acid is present, it will bind to the nitrocellulose.
  • the robot arm will then add a sample of a specific primer(s) for the HIV genetic material and the reagents necessary to carry out the nucleic acid amplification. Then the computer controls the heating- cooling system. After 30-50 cycles, the viral nucleic acid sequence is amplified approximately 1,000,000 times. The robot transfers the samples into another nitrocellulose plate. The amplified nucleic acid is allowed to bind onto the nitrocellulose and then a specific HIV probe (or combination of probes) is added. These probes are tagged with biotin or a hapten (Boerhinger Mannheim) so that they can be detected by a streptavidin or anti-hapten urease conjugate.
  • biotin or a hapten Boerhinger Mannheim
  • the robot arm washes the plate and adds the urea substrate.
  • the conductivity values are then read by the apparatus of the present invention and processed by the computer.
  • This method can be used for virtually any nucleic acid sequence. This method allows for a relatively rapid quantification of the amount of viral genetic material per volume of blood (or number of cells) and, most importantly, it does it without any human handling except the placing of the patients' samples in the plate wells.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Immunology (AREA)
  • Engineering & Computer Science (AREA)
  • Molecular Biology (AREA)
  • Biomedical Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Hematology (AREA)
  • Urology & Nephrology (AREA)
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Abstract

On décrit un procédé et un appareil nouveaux et améliorés servant à effectuer l'analyse par immunocaptation enzymatique de la présence d'une substance biologique dans un substrat fluide, et où un conjugué enzymatique est utilisé pour entrer en réaction avec la substance biologique afin de provoquer la libération d'ions dans le substrat. On mesure les modifications produites dans la résistivité du substrat par la libération des ions et un signal analogique est produit en réponse à cette mesure. Le signal analogique est converti en un signal numérique qui est quantifié puis restitué sous une forme lisible afin d'indiquer la quantité de la substance biologique présente dans le substrat.
PCT/US1991/002448 1991-06-06 1991-06-20 Procede et appareil de detection electrochimique de substances biologiques Ceased WO1992021959A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US71129191A 1991-06-06 1991-06-06
US711,291 1991-06-06

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WO1992021959A1 true WO1992021959A1 (fr) 1992-12-10

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000022431A1 (fr) * 1998-10-09 2000-04-20 Simon Feldberg Procede et appareil permettant de determiner et d'evaluer des populations bacteriennes
DE19950785A1 (de) * 1999-10-21 2001-05-23 Kist Europ Korea I Of Science Elektrochemischer Enzymimmunoassay
WO2003012419A1 (fr) * 2001-07-06 2003-02-13 Bioett Ab Capteur d'humidite
EP1203093A4 (fr) * 1999-06-17 2003-03-19 Gilead Sciences Inc Ligands d'acide nucleique a base de 2'-fluoropyrimidine et diriges contre la phosphatase intestinale du veau

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US3915804A (en) * 1974-07-15 1975-10-28 Corning Glass Works Apparatus and method for measuring conductivity change in a urea-urease reaction
US3963984A (en) * 1974-11-04 1976-06-15 Coulter Electronics, Inc. Method and system for cleaning an aperture in a particle study device
US4225410A (en) * 1978-12-04 1980-09-30 Technicon Instruments Corporation Integrated array of electrochemical sensors
US4230983A (en) * 1978-11-24 1980-10-28 Agro Sciences, Inc. Seed viability analyzer
US4713347A (en) * 1985-01-14 1987-12-15 Sensor Diagnostics, Inc. Measurement of ligand/anti-ligand interactions using bulk conductance
US4801546A (en) * 1983-06-29 1989-01-31 Metal Box Public Limited Company Apparatus for detecting micro-organisms

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Publication number Priority date Publication date Assignee Title
US3915804A (en) * 1974-07-15 1975-10-28 Corning Glass Works Apparatus and method for measuring conductivity change in a urea-urease reaction
US3963984A (en) * 1974-11-04 1976-06-15 Coulter Electronics, Inc. Method and system for cleaning an aperture in a particle study device
US4230983A (en) * 1978-11-24 1980-10-28 Agro Sciences, Inc. Seed viability analyzer
US4225410A (en) * 1978-12-04 1980-09-30 Technicon Instruments Corporation Integrated array of electrochemical sensors
US4801546A (en) * 1983-06-29 1989-01-31 Metal Box Public Limited Company Apparatus for detecting micro-organisms
US4713347A (en) * 1985-01-14 1987-12-15 Sensor Diagnostics, Inc. Measurement of ligand/anti-ligand interactions using bulk conductance

Non-Patent Citations (1)

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Title
P. THIJSSEN, "Caboratory Techniques in Biochemistry and Molecular Biology: Practice and Theory of Enzyme immunoassays", Published 1985, by ELSEVIER SCIENCE PUBLISHERS (AMSTERDAM), see pages 270-276. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000022431A1 (fr) * 1998-10-09 2000-04-20 Simon Feldberg Procede et appareil permettant de determiner et d'evaluer des populations bacteriennes
EP1203093A4 (fr) * 1999-06-17 2003-03-19 Gilead Sciences Inc Ligands d'acide nucleique a base de 2'-fluoropyrimidine et diriges contre la phosphatase intestinale du veau
US6673553B2 (en) 1999-06-17 2004-01-06 Gilead Sciences, Inc. 2′-fluoropyrimidine anti-calf intestinal phosphatase nucleic acid ligands
DE19950785A1 (de) * 1999-10-21 2001-05-23 Kist Europ Korea I Of Science Elektrochemischer Enzymimmunoassay
DE19950785C2 (de) * 1999-10-21 2002-08-01 Kist Europ Korea I Of Science Verfahren zur Durchführung eines Elektrochemischen Enzymimmunoassays
WO2003012419A1 (fr) * 2001-07-06 2003-02-13 Bioett Ab Capteur d'humidite
US7071830B2 (en) 2001-07-06 2006-07-04 Bioett Ab Moisture sensor

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