Electrochemical Biosensors Overview
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Questions and Answers

A transducer is a device that converts variations in a physical quantity into an ______ signal.

electrical

In a biosensor, the transducer converts biochemical interactions into measurable ______ signals.

electric

Sensors are devices that convert a physical parameter to an electrical ______.

output

Actuators are devices that convert an electrical signal to a physical ______.

<p>output</p> Signup and view all the answers

Amperometric transduction measures the current that flows, which is directly proportional to the analyte ______.

<p>concentration</p> Signup and view all the answers

To increase the selectivity of the detecting electrode in amperometric transduction, ______ are commonly used.

<p>membranes</p> Signup and view all the answers

One type of biosensor based on electrochemical reactions is the ______ biosensor.

<p>potentiometric</p> Signup and view all the answers

Cellulose acetate and Nafion are examples of ______ used in biosensors.

<p>membranes</p> Signup and view all the answers

Ion-selective electrodes are used to determine changes in concentration of chosen ______, e.g., hydrogen ions.

<p>ions</p> Signup and view all the answers

Polymeric membrane electrodes are commercially available for the selective detection of several ______ such as K+, Na+, and Ca2+.

<p>ions</p> Signup and view all the answers

Ion Selective Field Effect Transistors (ISFETs) are miniature ______ made using CMOS technology.

<p>ISEs</p> Signup and view all the answers

ISE-based biosensors are mainly used for ______ and creatinine measurement.

<p>urea</p> Signup and view all the answers

Elevated creatinine level signifies impaired kidney ______ or kidney disease.

<p>function</p> Signup and view all the answers

Amplified potentiometric transduction of DNA hybridization involves liposome 'nanocarriers' loaded with signaling ______.

<p>ions</p> Signup and view all the answers

Conductivity is a measurement of the ability of a solution to conduct an electric ______.

<p>current</p> Signup and view all the answers

Instruments measure conductivity by placing two plates of conductive material with known area and distance apart in a ______.

<p>sample</p> Signup and view all the answers

Mediators are artificial electron acceptor molecules that serve as an e- transfer shuttle to facilitate __________ transfer from the active site of the enzyme to the electrode.

<p>electron</p> Signup and view all the answers

To achieve lower applied potential for the oxidation of enzymatically generated H2O2, electrodes are metallised using noble metals like __________ and palladium.

<p>platinum</p> Signup and view all the answers

Polymers such as __________ can be employed to prevent interfering species from reaching the electrode surface.

<p>polypyrrole</p> Signup and view all the answers

The wearable tattoo-based alcohol biosensing system induces sweat through the transdermal delivery of the drug __________ using iontophoresis.

<p>pilocarpine</p> Signup and view all the answers

Amperometric detection of __________ in generated sweat utilizes the alcohol-oxidase enzyme.

<p>ethanol</p> Signup and view all the answers

A potentiometric biosensor measures the potential under __________ current conditions.

<p>zero</p> Signup and view all the answers

The potential generated in a potentiometric biosensor is directly proportional to the logarithm of the __________ concentration.

<p>analyte</p> Signup and view all the answers

The setup includes a scheme of the wireless operation for transdermal alcohol __________.

<p>sensing</p> Signup and view all the answers

A voltage potential is applied and the resulting current is measured in a technique that assesses changes in ionic ______.

<p>concentrations</p> Signup and view all the answers

The developed biosensor is based on the inhibition of the activity of alkaline ______, which is immobilized on the glass internal surface.

<p>phosphatase</p> Signup and view all the answers

Optical sensors rely on optical ______ of the signal and comprise spectrophotometry in different light ranges.

<p>transduction</p> Signup and view all the answers

In colorimetric detection of a western blot, the signal generated is a ______ precipitate.

<p>colored</p> Signup and view all the answers

Chemiluminescence detection emits ______ as a signal during the detection process.

<p>light</p> Signup and view all the answers

Photonic crystals are periodic optical nanostructures that can selectively couple energy at particular ______.

<p>wavelengths</p> Signup and view all the answers

Miniaturization in optical transducers allows for ______ measurements to be conducted.

<p>in vivo</p> Signup and view all the answers

A disadvantage of optical transducers is that ambient light is a strong ______.

<p>interferent</p> Signup and view all the answers

PC biosensors have been applied to the detection of antibody–antigen and small molecule–protein interactions, as well as ______-based assays.

<p>cell</p> Signup and view all the answers

The PCs utilized in the biomolecular interaction detection system are composed of an epoxy-cured polycarbonate ______ that is coated with a thin layer of TiO2.

<p>diffraction grating</p> Signup and view all the answers

Binding of macromolecules is monitored by shifts of nanometres in wavelength with a sensitivity of less than ______ pg/mm2.

<p>1</p> Signup and view all the answers

Crystalline colloidal arrays (CCA) self-assembled because of electrostatic ______ between particles.

<p>repulsion</p> Signup and view all the answers

The hydrogel is functionalized with a molecular recognition agent, which interacts with the analyte to actuate either shrinking or ______.

<p>swelling</p> Signup and view all the answers

Surface Plasmon Resonance (SPR) is an optical phenomenon due to a charge density oscillation at the interface of a ______ and a dielectric.

<p>metal</p> Signup and view all the answers

In the Kretschmann configuration, prisms are coated with a thin film of metal, usually gold or ______.

<p>silver</p> Signup and view all the answers

Above a certain incidence angle, all of the light is ______.

<p>reflected</p> Signup and view all the answers

The phenomenon known as ______ Internal Reflection (TIR) is important in optical transducers.

<p>Total</p> Signup and view all the answers

Calorimetric transducers measure the heat produced by the reaction, using the formula ΔT = nΔH/cp, where ΔH represents the ______.

<p>enthalpy</p> Signup and view all the answers

The Quartz crystal microbalance (QCM) utilizes the ______ Effect to measure mass changes.

<p>Converse Piezoelectric</p> Signup and view all the answers

Sauerbrey proved that the oscillation frequency of the quartz crystal is dependent on the ______ change.

<p>mass</p> Signup and view all the answers

Cantilever-based sensors are a type of ______ free biosensor that is simple and cost-effective.

<p>label</p> Signup and view all the answers

In mass sensitive sensors like QCM, the amount of mass accumulated on the surface affects the ______ frequency.

<p>crystal</p> Signup and view all the answers

In enzyme-catalyzed reactions, considerable heat evolution can range from 5 to ______ kJ/mol.

<p>100</p> Signup and view all the answers

Cantilevers bend as a result of specific ______ occurring on their surface.

<p>binding</p> Signup and view all the answers

Flashcards

Transducer

A device that converts variations in a physical quantity (like pressure or temperature) into an electrical signal, or vice versa.

Biosensor transducer

A transducer specifically used in biosensors to convert biochemical interactions into measurable electrical signals.

Amperometric transduction

A type of electrochemical biosensor where a constant electrode potential enables the measurement of the current related to analyte concentration, often using enzymes.

Electrochemical biosensor

Biosensors utilizing electrochemical reactions at the electrode-electrolyte interface to detect biochemical interactions.

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Sensor

A device that converts a physical parameter into an electrical output.

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Actuator

A device that converts an electrical signal into a physical output.

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Membrane (biosensor)

A component used to improve biosensor selectivity and prevent interference in biosensor analysis.

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Discriminative membrane

Membranes used in biosensors for preventing fouling, eliminating interference and controlling operating conditions.Different materials will have specific properties and advantages.

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Mediators (in amperometric transduction)

Artificial electron acceptor molecules that shuttle electrons from an enzyme's active site to an electrode, facilitating the electrochemical reaction.

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Metallised electrodes

Electrodes coated with a noble metal (e.g., platinum, palladium) to enhance the catalytic oxidation of substances like H2O2 at lower applied voltages.

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Polymers (in biosensors)

Substances used to create barriers that prevent unwanted substances (interfering species) from reaching the electrode surface, improving selectivity.

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Potentiometric transduction

A method that measures the potential difference (voltage) generated by the interaction of an analyte with a specific material. The potential is proportional to the log of the analyte concentration.

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Iontophoresis

A technique for transdermal drug delivery using an electric current to drive charged molecules (drugs, analytes) through the skin.

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Alcohol biosensor

A sensor that detects alcohol in sweat or other fluids, enabling portable and non-invasive monitoring.

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Wearable tattoo-based biosensor

A biosensor designed as a patch, allowing transdermal delivery of stimulating agents (e.g., pilocarpine) to induce sweat production, enabling noninvasive sampling of alcohol in sweat.

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Ion-selective electrode (ISE)

A device measuring changes in ion concentrations, often used for detecting specific ions in solutions.

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Ion Selective Field Effect Transistor (ISFET)

A miniaturized, solid-state version of an ion selective electrode.

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ISE-based biosensor

A sensor that uses an ion-selective electrode to detect specific molecules related to a biological process.

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Creatinine

A molecule; its concentration in blood is a measure of kidney function.

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Conductivity

A solution's ability to carry an electrical current.

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Conductometric transduction

A technique for measuring changes in conductivity.

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DNA hybridization

The binding of complementary DNA sequences.

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Conductometric Biosensor

A biosensor that measures changes in ionic concentration to detect a substance.

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Optical Transducer

A device that converts a physical signal into an optical signal.

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Western Blot

A method for detecting specific proteins in a sample.

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Colorimetric Detection (Western Blot)

A Western blot method where a colored precipitate forms upon detection

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Chemiluminescence Detection

A technique where light is emitted from a chemical reaction.

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Fluorescence Detection

A technique where a fluorophore emits light when exposed to specific wavelengths.

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Photonic Crystal

A material with a repeating nanostructure that selectively transmits or reflects light at specific wavelengths.

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Miniaturization (Biosensors)

The process of making biosensors smaller.

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PC Biosensor

A biosensor that employs photonic crystals (PCs) to detect biomolecular interactions. These PCs are designed to change their optical properties (like color) in response to specific molecular binding events.

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Biomolecular Interaction Detection System

A system that uses PCs to monitor biomolecule binding. These PCs are made from a polycarbonate diffraction grating coated with titanium dioxide (TiO2), and changes in light wavelength reveal binding events.

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CCA (Crystalline Colloidal Array)

A regular, 3D arrangement of tiny particles that diffracts visible light. It's like a mini-rainbow maker! The spacing between these particles determines the colors we see.

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PCCA (Polymerized CCA)

A CCA that's been embedded in a polymerized hydrogel network. This creates a stable, functionalized structure for sensing.

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How does analyte binding change PC color?

Analytes bind to recognition agents on the PC, causing the hydrogel to swell or shrink. This alters the spacing of the CCA, shifting the diffracted wavelength and changing the PC's color perception.

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Surface Plasmon Resonance (SPR)

Optical phenomenon at the interface of a metal and dielectric material. The light interacts with the electrons in the metal, creating a wave-like oscillation called a plasmon.

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Kretschmann Configuration

An experimental set-up using prisms coated with a thin layer of gold/silver to observe SPR. Light incident on the prism at a specific angle triggers the plasmon resonance.

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SPR Detection

An optical method to monitor biomolecular interactions based on SPR. Binding events change the refractive index at the metal surface, altering the SPR signal.

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Total Internal Reflection (TIR)

When light traveling in a denser medium (like water) hits a boundary with a less dense medium (like air) at a steep angle, it reflects back into the denser medium. This happens because the light bends so much that it doesn't have enough energy to escape the denser medium.

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Calorimetric Transducer

A transducer that measures the heat produced by a chemical reaction. The amount of heat is proportional to the concentration of the analyte.

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Quartz Crystal Microbalance (QCM)

A mass-sensitive transducer that utilizes a piezoelectric quartz crystal. The crystal oscillates at a specific frequency. When mass is added to the crystal's surface, the frequency changes, indicating the amount of mass added.

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Sauerbrey Equation

A mathematical equation that relates the change in frequency of a QCM to the mass added to the crystal's surface. This equation helps to calculate the concentration of the analyte.

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Cantilever Biosensor

A label-free biosensor that uses a tiny, flexible beam (cantilever) to detect analytes. When a specific analyte binds to the cantilever's surface, it bends due to the added mass. The bending is measured to determine the concentration of the analyte.

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Label-Free Biosensor

A biosensor that doesn't require any chemical labels to detect the analyte. This means the analyte can be detected directly without modifying it.

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Study Notes

Transducers

  • A device that converts variations in a physical quantity (e.g., pressure, temperature, brightness) into an electrical signal, or vice versa.
  • In a biosensor, the transducer converts biochemical interactions into measurable electrical signals.
  • Types of Physical Quantities Converted:
    • Thermal: temperature, heat flow
    • Mechanical: position, acceleration, force, pressure
    • Chemical: concentration, composition, reaction rate
    • Optical: intensity, wavelength, polarization
    • Magnetic: field intensity, flux
    • Electrical: voltage, current, charge

Sensors and Actuators

  • Sensors: Devices that convert a physical parameter into an electrical output.
  • Actuators: Devices that convert an electrical signal into a physical output.

Electrochemical Biosensors

  • Detect electrochemical reactions at the electrode-electrolyte interface.
  • Types:
    • Potentiometric
    • Amperometric
    • Conductometric

Amperometric Transduction

  • Electrode potential is maintained at a constant level for oxidation/reduction.
  • Current flow is proportional to the analyte concentration.
  • Prone to interference by exogenous oxygen.
  • Commonly utilizes enzyme electrodes based on oxidases, combined with hydrogen peroxide indicators.

Increasing Selectivity in Amperometric Transduction

  • Using membranes: examples include cellulose acetate, Nafion, polycarbonate
  • Using mediators: artificial electron acceptor molecules facilitate electron transfer from enzyme to electrode.
  • Using metallised electrodes: electrodeposition of noble metals (platinum, palladium, rhodium, ruthenium) creates highly catalytic surfaces.
  • Using polymers: polymers can prevent interfering species from reaching the electrode surface (e.g., polypyrrole).

Potentiometric Transduction

  • Monitors potential (relative to a reference) under zero current conditions.
  • Potential is directly proportional to the logarithm of the analyte concentration.
  • Ion-selective electrodes are used to measure changes in ion concentration.
  • Example: pH electrode.

ISE (Ion Selective Electrode)

  • Polymeric membrane electrodes are commercially available.
  • Used to selectively detect ions in complex biological matrices (e.g., K+, Na+, Ca2+, NH4+, H+, CO32-).

Noninvasive Alcohol Monitoring System

  • Wearable tattoo-based system uses iontophoresis to deliver pilocarpine and induce sweat.
  • Analyzes sweat for ethanol concentration using alcohol oxidase enzyme and Prussian Blue electrode.
  • Offers highly selective and sensitive detection of ethanol.

Other Biosensor Types (with examples)

  • Calorimetric: Measures heat produced during a reaction. (Examples: Catalase on hydrogen peroxide, Cholesterol oxidase on cholesterol)
  • Optical: Uses light for transduction. (Examples: photonic crystals, SPR, fluorescence resonance energy transfer (FRET).
  • Mass sensitive (QCM): Measures mass changes based on frequency changes in a piezoelectric quartz crystal.

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Description

This quiz explores the concepts of transducers, sensors, and actuators, focusing on how they convert various physical quantities into electrical signals. Additionally, it delves into different types of electrochemical biosensors and their operational principles. Test your knowledge on these essential technologies and their applications.

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