Biosensor transducers MCQs With Answer

Biosensor transducers MCQs With Answer

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Biosensor transducers MCQs With Answer is designed for M.Pharm students seeking a focused, advanced review of biosensor transduction principles relevant to pharmaceutical biotechnology. This collection emphasizes in-depth understanding of electrochemical, optical, mass-sensitive and thermal transducers, their operating principles, performance metrics (sensitivity, limit of detection, selectivity, response time, drift), and practical considerations for drug monitoring, bioprocess control and pathogen detection. Questions cover device architecture (three-electrode systems, ISFETs, QCM, SPR), signal amplification strategies, immobilization impacts, nanomaterial enhancement, noise sources and calibration methods. Use these problems to reinforce theoretical foundations and apply concepts to real-world pharmaceutical sensor development and validation.

Q1. Which transducer principle measures analyte concentration by monitoring the potential difference between a working electrode and a reference electrode without passing significant current?

  • Amperometric transduction
  • Potentiometric transduction
  • Conductometric transduction
  • Piezoelectric transduction

Correct Answer: Potentiometric transduction

Q2. In an amperometric biosensor for glucose using glucose oxidase, what is the main function of a redox mediator like ferrocene derivatives?

  • To immobilize the enzyme on the electrode surface
  • To shuttle electrons between the enzyme active site and the electrode, reducing overpotential
  • To change the pH near the electrode for better enzyme activity
  • To increase mass sensitivity by adding mass to the sensing layer

Correct Answer: To shuttle electrons between the enzyme active site and the electrode, reducing overpotential

Q3. Which optical transducer technique detects refractive index changes at a sensor surface and is widely used for label-free kinetic binding studies?

  • Fluorescence resonance energy transfer (FRET)
  • Surface plasmon resonance (SPR)
  • Photoluminescence quenching
  • Raman scattering

Correct Answer: Surface plasmon resonance (SPR)

Q4. What primary advantage does a quartz crystal microbalance (QCM) transducer offer for studying biomolecular interactions?

  • High electrical conductivity of the sensing layer
  • Direct, real-time mass change measurement with nanogram sensitivity
  • Inherent fluorescence labeling of captured species
  • Ability to measure pH changes directly

Correct Answer: Direct, real-time mass change measurement with nanogram sensitivity

Q5. Which parameter most directly describes the smallest analyte concentration change a biosensor can reliably detect?

  • Dynamic range
  • Limit of detection (LOD)
  • Response time
  • Shelf life

Correct Answer: Limit of detection (LOD)

Q6. In ISFET-based potentiometric sensors, what is the role of the ion-sensitive layer at the gate insulator?

  • To facilitate electron tunneling to the substrate
  • To selectively interact with target ions and modulate surface potential altering channel current
  • To emit photons proportional to ion concentration
  • To mechanically vibrate in response to ionic binding

Correct Answer: To selectively interact with target ions and modulate surface potential altering channel current

Q7. Which noise source becomes dominant in many electrochemical biosensors at very low analyte concentrations and limits detection?

  • Thermal (Johnson) noise
  • Shot noise associated with discrete electron transfer events
  • 1/f (flicker) noise from electrode surface processes
  • Electromagnetic interference from nearby equipment

Correct Answer: 1/f (flicker) noise from electrode surface processes

Q8. Label-free biosensors are preferred for kinetic analysis because they:

  • Require fluorescent tags to increase signal intensity
  • Avoid perturbation of binding interactions by labels and directly monitor intrinsic signals
  • Always provide lower limits of detection than labeled assays
  • Use thermal amplification to increase sensitivity

Correct Answer: Avoid perturbation of binding interactions by labels and directly monitor intrinsic signals

Q9. For an enzymatic amperometric sensor operating under diffusion-limited conditions, which change will most likely improve response time?

  • Increase enzyme loading to form a thicker catalytic film
  • Decrease stirring or convection near the electrode
  • Reduce diffusion path length by making the sensing layer thinner or porous
  • Eliminate mediator molecules to simplify electron transfer

Correct Answer: Reduce diffusion path length by making the sensing layer thinner or porous

Q10. Which transducer type directly converts a biochemical reaction’s heat release into a measurable signal?

  • Calorimetric (thermal) transducer
  • Electrochemical potentiometric transducer
  • Optical fluorescence transducer
  • Piezoelectric acoustic transducer

Correct Answer: Calorimetric (thermal) transducer

Q11. When designing an immunosensor for therapeutic drug monitoring, which immobilization strategy generally preserves antibody orientation and antigen-binding activity best?

  • Random physical adsorption on hydrophobic surfaces
  • Covalent coupling via amino groups without controlling orientation
  • Oriented immobilization using Protein A/G or Fc-specific linkers
  • Entrapment within thick non-porous polymers

Correct Answer: Oriented immobilization using Protein A/G or Fc-specific linkers

Q12. Which statement best describes the Nernstian response in potentiometric biosensors?

  • Potential changes linearly with current according to Ohm’s law
  • Potential changes logarithmically with ion activity, typically 59 mV per decade for monovalent ions at 25°C
  • Potential is independent of analyte concentration and depends only on temperature
  • Potential is proportional to mass change on a vibrating crystal

Correct Answer: Potential changes logarithmically with ion activity, typically 59 mV per decade for monovalent ions at 25°C

Q13. Which nanomaterial modification is commonly used to enhance electron transfer rates and surface area in electrochemical biosensors?

  • Polystyrene beads
  • Carbon nanotubes or graphene
  • Silicone oil layers
  • Calcium carbonate crystals

Correct Answer: Carbon nanotubes or graphene

Q14. In a field-effect transistor (FET) biosensor, what primary effect does analyte binding at the gate have on device characteristics?

  • Shifts the threshold voltage and modulates channel current
  • Increases the mechanical resonance frequency
  • Generates fluorescence emission proportional to binding
  • Directly produces a measurable heat pulse

Correct Answer: Shifts the threshold voltage and modulates channel current

Q15. Which calibration strategy best compensates for sensor drift during long-term continuous monitoring in bioprocessing?

  • Single-point calibration at manufacture only
  • Periodic multi-point recalibration using matrix-matched standards or on-line reference channels
  • Avoid calibration and apply post-hoc mathematical smoothing
  • Calibrate with distilled water between runs

Correct Answer: Periodic multi-point recalibration using matrix-matched standards or on-line reference channels

Q16. What is the main limitation of fluorescence-based biosensor transducers in complex pharmaceutical matrices?

  • They cannot achieve high sensitivity
  • Background autofluorescence and scattering from the matrix can reduce signal-to-noise ratio
  • They inherently lack specificity for biomolecules
  • They require piezoelectric substrates to function

Correct Answer: Background autofluorescence and scattering from the matrix can reduce signal-to-noise ratio

Q17. Which modification enhances selectivity of an electrochemical aptasensor toward a small-molecule drug?

  • Using a generic thiol self-assembled monolayer without aptamer
  • Incorporating a high-affinity, drug-specific aptamer and antifouling surface chemistry
  • Maximizing hydrophobic polymer coating thickness
  • Removing the recognition element and increasing electrode area

Correct Answer: Incorporating a high-affinity, drug-specific aptamer and antifouling surface chemistry

Q18. Which approach is most effective to lower the noise floor and improve LOD in electrochemical biosensors during measurement?

  • Increase measurement bandwidth to include more frequencies
  • Use differential or reference electrode configurations and low-noise amplification with proper shielding
  • Operate the sensor at very high temperatures to reduce viscosity
  • Remove all reference electrodes to simplify the circuit

Correct Answer: Use differential or reference electrode configurations and low-noise amplification with proper shielding

Q19. Which characteristic of a biosensor is best described by the slope of a calibration curve in the linear range?

  • Specificity
  • Sensitivity (analytical sensitivity)
  • Limit of detection
  • Response time

Correct Answer: Sensitivity (analytical sensitivity)

Q20. When integrating a biosensor into a point-of-care device for therapeutic drug monitoring, which factor is most critical for clinical utility?

  • Complexity of signal processing algorithms irrespective of usability
  • Rapid response, adequate accuracy/precision, minimal sample preparation and robustness in real biological matrices
  • Maximal electrode surface area without regard to reproducibility
  • Exclusive reliance on labeled assays requiring long incubation times

Correct Answer: Rapid response, adequate accuracy/precision, minimal sample preparation and robustness in real biological matrices

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