Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
  • G01N29/348—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with frequency characteristics, e.g. single frequency signals, chirp signals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/02—Analysing fluids
  • G01N29/022—Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
  • G01N29/4409—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison
  • G01N29/4418—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison with a model, e.g. best-fit, regression analysis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/01—Indexing codes associated with the measuring variable
  • G01N2291/014—Resonance or resonant frequency
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/01—Indexing codes associated with the measuring variable
  • G01N2291/018—Impedance
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/02—Indexing codes associated with the analysed material
  • G01N2291/025—Change of phase or condition
  • G01N2291/0255—(Bio)chemical reactions, e.g. on biosensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/02—Indexing codes associated with the analysed material
  • G01N2291/025—Change of phase or condition
  • G01N2291/0256—Adsorption, desorption, surface mass change, e.g. on biosensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/04—Wave modes and trajectories
  • G01N2291/042—Wave modes
  • G01N2291/0422—Shear waves, transverse waves, horizontally polarised waves

Definitions

• This invention relates to a process of detecting specific molecules in a liquid (the analyte) with receiving molecules, (the receptors) which are attached to the surface of a thickness shear mode acoustic sensor (TSM). Acoustic energy generated in the sensor is transferred to and from the fluid depending on the surface coupling behaviour. The coupling is altered when the analyte binds to the receptor producing easily measured changes in the electrical characteristics of the sensor.
• TSM thickness shear mode acoustic sensor
• the invention further relates to the application of the measurement of the coupling effects to the sensing of biomolecules, and other molecules of biological significance such as drugs, in general.
• the receptor may be a protein, a single oligonucleotide strand, DN A or RN A and the analyte a protein, drug or complementary strands of DNA or RNA.
• the interaction between the analyte and the sensor bound receptor can be identified through a quantitative TSM response.
• Other measurement scenarios are possible through the detection of changes in the acoustic coupling between the sensor surface and the surrounding liquid.
• a TSM sensor is a device which generates mechanical vibrations from an electrical signal and uses these vibrations to detect and/or quantify particular chemical or biochemical substances present in a medium surrounding the sensor (the analyte). Acoustic energy is stored and dissipated both in the device itself, and through interfacial coupling, in a surrounding liquid medium. By coating the sensor with one or more layers of a substance which interacts with the analyte, the energy storage and transfer processes change when the interaction occurs. This changes the acoustic resonance of the sensor, which can be observed by measuring the electrical impedance of the sensor.
• the applicants have published several papers in this field and they are listed as follows:
• TSM sensor responds to chemical change on its surface when it is immersed in a liquid.
• Surface mass deposition occurs when the analyte binds to the receptor on the sensor surface. This increases the storage of acoustic energy through the inertia of the added mass. Acoustic energy may also be stored through the elastic deformation of a coating on the surface. The elasticity of the coating may also change when the analyte binds to the receptor coating.
• These energy storage modes determine the resonant characteristics of the sensor which can easily be measured electrically. These processes are well known. Examples of piezoelectric sensors are described, for example in U.S. Patents 5,374,521 and 5,658,732.
• Viscous loading occurs when acoustic energy is transferred to the liquid. Some of the acoustic energy is stored by the inertia of the fluid moving with the sensor surface and can be transferred back to the sensor, but acoustic energy is also dissipated by internal friction within the fluid.
• the viscous loading effect is also well known, however in the current use of this effect, the transfer of acoustic energy at the surface is considered to be perfect, that is, there is no slip between the sensor surface and the adjacent fluid molecules.
• the motional inductance, L M represents the inertial energy stored by the sensor. It depends on the mass of the TSM sensor as well as the mass of material (the analyte) added to the surface. Since liquid coupled to the surface can store and return acoustic energy, L M is also dependent on the viscosity of the liquid.
• the motional resistance, R M is intrinsically related to the energy dissipated by the sensor.
• the motional capacitance, C M represents the elastic energy stored by the sensor.
• the absorption or chemical binding of the analyte to the coating can have a large effect on the viscoelastic properties of the coating.
• an added (or removed) layer of material may change the elasticity of the sensor and thus affect C M .
• most fluids are considered to be viscous, at the high frequencies used in piezoelectric quartz sensors, the liquid may also have elastic properties.
• the static capacitance C 0 represents the dielectric constant of the quartz, but includes that of the medium through the electric field. Charge interactions between the analyte and the sensor coating will affect this value.
• a process for sensing biological or chemical changes in molecular structural shape or mass of molecules attached to the surface of a transverse shear piezoelectric oscillating molecular sensing device driven by a network analyzer comprising: i) exciting said sensor device at a series of predetermined frequencies; ii) collecting data to determine values for the predetermined parameters of series resonance frequency shift (fS), motional resistance (RM), motional inductance (LM), motional capacitance (CM), electrostatic capacitance (Co) and boundary layer slip parameter ( ⁇ ); and iii) determining relative changes in said measured parameters to detect thereby any changes in molecular structural shape or mass at sensing device surface.
• fS series resonance frequency shift
• RM motional resistance
• LM motional inductance
• CM motional capacitance
• Co electrostatic capacitance
• ⁇ boundary layer slip parameter
• a method of determining the efficiency of acoustic coupling between a sensor and the surrounding fluid comprising: a) applying an electrical signal of known frequency and voltage to the sensor; b) measuring the current through the sensor to determine the impedance at the known frequency; c) repeating steps a) and b) over a range of frequencies to generate a set of impedance data; and d) fitting the measured impedance data to determine an ⁇ parameter which represents coupling strength.
• this coupling determines the strength of the viscous loading and elastic effects depending on such parameters as the surface free energy and the molecular conformation of the sensor coating. These molecular parameters are very sensitive to chemical changes at the surface and therefore acoustic coupling provides a novel sensing mechanism.
• the impedance measurements are carried out by applying an electrical signal of known frequency and voltage to the sensor and measuring the current through the sensor. Through Ohm's law, this provides the impedance at the known frequency. By performing this measurement over a range of frequencies, a set of data is generated.
• the above described, specifically selected parameters of L M , R M , C and C 0 have been found to be the determining parameters for indicating a mass or conformation change at the TSM surface. Hence these parameters are fitted to the data. While the Butterworth - van Dyke model provides useful information, it is an electrical analogy which presents the information unclearly.
• An alternate model of the TSM sensor is based on a solution of the equations of motion and electric fields.
• the deposited mass and the coupling may be determined directly by fitting the electrical impedance data obtained as above.
• the coupling is represented by a slip parameter, ⁇ , which arises from a slip boundary condition used in solving the set of equations.
• ⁇ is taken to be a complex number which is determined by fitting the measured impedance data.
• Ligands for biological macromolecules include small molecules, ions, proteins, peptides, and strands of both DNA and RNA.
• the interaction of these entities with the biological molecules attached to the sensor will cause an alteration of the physical properties of the film resulting, in turn, in changes in the measured parameters. These changes will very clearly result from a combination of some or all of the above response mechanisms particular for each chemical situation. In this regard, the dimensions of the newly bound ligand is an important consideration.
• the signaling species coated onto the acoustic biosensor are proteins
• HIV-I human immunodeficiency virus type I
• Tat an 86-amino acid protein
• TAR-Tat system is an important target for drug discovery research because the binding of the regulatory protein to TAR can be blocked by small molecules.
• the slip parameter ⁇ for the binding of Tat-derived peptides to TAR immobilized on a sensor surface.
• the TAR RNA is synthesized, with a biotin moiety at the 5 ' -end, on a DNA synthesizer by standard phosphoramidite chemistry.
• the acoustic wave sensor is incorporated into a flow-through configuration and electrically connected to an acoustic network analyzer. A dispersion of 100-500 ⁇ l of the reagent neutravidin is injected into the apparatus and the protein adsorbs to the gold electrode surface of the acoustic wave sensor.
• a dispersion of biotinylated TAR- RNA (100-500 ⁇ l) is introduced into the system where the formation of the biotin-avidin complex results in attachment of TAR to the sensor surface.
• Various Tat- derived peptides are then introduced into the flow-trough system.
• the following peptides are specified: tat 12 , tat 20 , and tat 30 where the subscript refers to the number of amino acids in the peptide.
• Dispersions of peptide (100-500 ⁇ l) are injected into the system. On binding of peptide to TAR in real time transient responses in the aforementioned parameters are obtained.
• the computed ⁇ x parameter for the various responses which distinguishes the nature on binding, are as follows:
• Tat 20 baseline 1.985 @21.42 degrees signal 1.926@ 18.15 degrees Tat 30 baseline 1.982 @ 22.61 degrees signal 1.994 @ 23.03 degrees
• Tat 12 displays a small decrease in slip magnitude with an increase in phase, whereas tat 20 shows large decreases in magnitude and phase.
• Tat 30 depicts smaller increase in magnitude and phase.

Landscapes

• Physics & Mathematics (AREA)
• Analytical Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Signal Processing (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=22560754

Family Applications (1)

Country Status (4)

Families Citing this family (10)

Family Cites Families (5)

• 2000
  • 2000-09-29 CA CA002386006A patent/CA2386006A1/en not_active Abandoned
  • 2000-09-29 AU AU75021/00A patent/AU7502100A/en not_active Abandoned
  • 2000-09-29 EP EP00963840A patent/EP1221049A1/de not_active Withdrawn
  • 2000-09-29 WO PCT/CA2000/001139 patent/WO2001023892A1/en not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events