Permeability testing: In-vitro methods MCQs With Answer

Permeability testing: In-vitro methods MCQs With Answer

Permeability testing bridges formulation design and prediction of in vivo drug absorption. This quiz set focuses on in‑vitro permeability techniques essential for M.Pharm students studying Modern Bio‑Analytical Techniques. Coverage includes cell‑based assays (Caco‑2, MDCK), artificial membrane assays (PAMPA), diffusion systems (Franz cell, Ussing chamber), and related analytical concepts such as apparent permeability (Papp), sink conditions, TEER, unstirred water layers, and validation criteria. Questions probe experimental design, calculation, interpretation, advantages and limitations of each method, and how in‑vitro results correlate with in‑vivo absorption. Use these MCQs to strengthen conceptual understanding and prepare for lab work and exams.

Q1. What is the primary limitation of the PAMPA (Parallel Artificial Membrane Permeability Assay) compared to cell‑based models?

• It requires live tissue and continuous oxygenation
• It cannot predict paracellular transport accurately
• It lacks active transporters and metabolic enzymes
• It is unable to determine passive diffusion

Correct Answer: It lacks active transporters and metabolic enzymes

Q2. In a Caco‑2 permeability experiment, transepithelial electrical resistance (TEER) is monitored because:

• TEER directly measures drug concentration in the receptor compartment
• High TEER indicates intact tight junctions and monolayer integrity
• Low TEER indicates high transcellular drug flux
• TEER gives the metabolic clearance rate of the monolayer

Correct Answer: High TEER indicates intact tight junctions and monolayer integrity

Q3. The apparent permeability coefficient (Papp) is most correctly calculated from which experimental data?

• The ratio of donor concentration to receptor volume at t=0
• The steady state slope of cumulative amount in receptor vs time, divided by donor concentration and membrane area
• The initial donor concentration divided by membrane thickness
• The total amount retained in the membrane after equilibrium

Correct Answer: The steady state slope of cumulative amount in receptor vs time, divided by donor concentration and membrane area

Q4. Which of the following is a commonly used biological surrogate for human skin in topical permeation studies?

• Rat intestinal mucosa
• Porcine ear skin
• Rabbit cornea
• Human red blood cells

Correct Answer: Porcine ear skin

Q5. If the slope dQ/dt = 1.0 × 10^-9 mol/s, effective membrane area A = 1.0 cm^2, and initial donor concentration C0 = 1.0 × 10^-4 mol/cm^3, what is the Papp (in cm/s)?

• 1.0 × 10^-3 cm/s
• 1.0 × 10^-5 cm/s
• 1.0 × 10^-6 cm/s
• 1.0 × 10^-4 cm/s

Correct Answer: 1.0 × 10^-5 cm/s

Q6. Which experimental practice most effectively minimizes the contribution of the unstirred water layer (UWL) during permeability assays?

• Using higher donor concentration without stirring
• Increasing membrane thickness
• Applying vigorous stirring or orbital shaking of the receptor compartment
• Reducing receptor solution ionic strength

Correct Answer: Applying vigorous stirring or orbital shaking of the receptor compartment

Q7. In an Ussing chamber experiment, which measurement indicates active transport or electrogenic ion movement across tissue?

• Permeability coefficient (Papp)
• Transepithelial electrical resistance (TEER) only
• Short‑circuit current (Isc) and potential difference
• Apparent volume of distribution

Correct Answer: Short‑circuit current (Isc) and potential difference

Q8. Which of the following correctly describes a sink condition in permeability testing?

• The donor concentration is kept constant by adding more drug during the experiment
• The receptor concentration remains much lower than donor concentration so that driving gradient is maintained
• The receptor compartment has no buffer capacity to avoid pH changes
• The donor is continually removed so its concentration stays below 10% of solubility

Correct Answer: The receptor concentration remains much lower than donor concentration so that driving gradient is maintained

Q9. Which in‑vitro method is best suited to screen passive transcellular permeability rapidly for large compound sets?

• Ussing chamber with fresh tissue
• PAMPA
• Caco‑2 transwell assay with 21‑day differentiation
• Franz diffusion cell with human epidermis

Correct Answer: PAMPA

Q10. Which statement about Caco‑2 cells is TRUE?

• They lack efflux transporters, so they only measure passive diffusion
• They form tight junctions and express P‑glycoprotein, making them useful for passive and active transport studies
• They are primary human enterocytes that must be used within 24 hours of isolation
• They are an artificial lipid membrane model used to mimic unstirred layers

Correct Answer: They form tight junctions and express P‑glycoprotein, making them useful for passive and active transport studies

Q11. When validating an in‑vitro permeability assay, which parameter ensures mass conservation and recovery during the experiment?

• TEER measurement
• Mass balance (donor + receptor + membrane recovery close to 100%)
• Apparent permeability coefficient (Papp)
• Short‑circuit current stability

Correct Answer: Mass balance (donor + receptor + membrane recovery close to 100%)

Q12. A high Papp measured in Caco‑2 does not always predict high oral bioavailability because:

• Caco‑2 assays overestimate first‑pass hepatic metabolism
• Oral bioavailability also depends on solubility, first‑pass metabolism, and efflux transporters in vivo
• Papp only measures paracellular transport which is irrelevant for most drugs
• Caco‑2 cells convert all drugs to inactive metabolites

Correct Answer: Oral bioavailability also depends on solubility, first‑pass metabolism, and efflux transporters in vivo

Q13. Which reagent is commonly used as a paracellular transport marker in permeability studies to assess tight junction integrity?

• Propranolol
• Mannitol
• Diazepam
• Testosterone

Correct Answer: Mannitol

Q14. In a Franz diffusion cell for topical formulation testing, what is the primary role of the receptor fluid?

• To simulate the donor formulation vehicle and maintain its viscosity
• To provide a well‑mixed medium that maintains sink conditions and physiological pH for the receiving side
• To fix the skin sample in place by crosslinking proteins
• To directly metabolize the permeant to mimic in vivo skin enzymes

Correct Answer: To provide a well‑mixed medium that maintains sink conditions and physiological pH for the receiving side

Q15. Which of the following is a common chemical permeation enhancer used in transdermal delivery studies?

• Tris buffer
• Polysorbate 80 (a surfactant)
• Sodium chloride at physiological concentration
• Citric acid as an oxidizer

Correct Answer: Polysorbate 80 (a surfactant)

Q16. Which of the following best explains why MDCK cells are sometimes used instead of Caco‑2 for permeability screening?

• MDCK cells express more human metabolic enzymes than Caco‑2
• MDCK form tighter junctions making them ideal for measuring only paracellular transport
• MDCK assays are faster and often more reproducible for high‑throughput screening, though they may differ in transporter expression from human intestinal cells
• MDCK are an artificial membrane that eliminates any transporter effects

Correct Answer: MDCK assays are faster and often more reproducible for high‑throughput screening, though they may differ in transporter expression from human intestinal cells

Q17. During permeability data interpretation, which observation most strongly suggests involvement of an efflux transporter such as P‑gp?

• Symmetrical permeability in apical→basolateral and basolateral→apical directions
• Higher basolateral→apical permeability compared to apical→basolateral, which is reduced on co‑incubation with a P‑gp inhibitor
• Complete lack of permeability in both directions
• Permeability that is independent of temperature

Correct Answer: Higher basolateral→apical permeability compared to apical→basolateral, which is reduced on co‑incubation with a P‑gp inhibitor

Q18. Which validation criterion should be checked when performing repeated sampling from the receptor compartment in a Franz or transwell study?

• The pH of the donor formulation only
• Maintenance of sink conditions and correction for sample removal (volume replacement and cumulative mass calculation)
• That the donor solution is static and not stirred
• That the membrane thickness increases during sampling

Correct Answer: Maintenance of sink conditions and correction for sample removal (volume replacement and cumulative mass calculation)

Q19. Effective permeability (Peff) derived from in vitro assays is most useful for which of the following translational applications?

• Predicting metabolic clearance in the liver quantitatively
• Estimating likely in vivo intestinal absorption and helping classify compounds by permeability for BCS or PBPK modeling
• Determining the exact plasma protein binding percentage in humans
• Directly measuring the drug’s half‑life in systemic circulation

Correct Answer: Estimating likely in vivo intestinal absorption and helping classify compounds by permeability for BCS or PBPK modeling

Q20. Which of the following experimental observations would most likely indicate loss of monolayer integrity in a transwell permeability assay?

• Stable TEER values over time and linear donor depletion
• Sudden large increase in paracellular marker flux (e.g., mannitol) and a ≥20% drop in TEER
• Decrease in receptor concentration below detection limit
• Constant apical pH with reduced donor concentration

Correct Answer: Sudden large increase in paracellular marker flux (e.g., mannitol) and a ≥20% drop in TEER

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