Microspheres and microcapsules MCQs With Answer

Microspheres and microcapsules MCQs With Answer are designed to help M. Pharm students master key principles of molecular pharmaceutics and novel drug delivery systems (NTDS). This quiz covers essential concepts such as classification, materials, preparation techniques (solvent evaporation, coacervation, interfacial polymerization, spray drying), characterization (SEM/TEM, DSC, FTIR, laser diffraction, zeta potential), release kinetics, mucoadhesion, floating systems, sterilization, regulatory limits, and scale-up considerations. Emphasis is placed on formulation strategy for hydrophilic and hydrophobic drugs, polymer selection (PLGA, gelatin, alginate, Eudragit), core–shell versus matrix structures, and factors affecting entrapment efficiency and stability. Use these MCQs to test understanding, prepare for exams, and strengthen practical decision-making in microencapsulation and microsphere-based delivery.

Q1. Which statement best distinguishes microspheres from microcapsules in pharmaceutical delivery systems?

• Microspheres are homogeneous matrix systems where drug is dispersed throughout the polymer; microcapsules have a distinct core surrounded by a polymeric shell
• Both microspheres and microcapsules always possess a core–shell structure
• Microspheres are always larger than microcapsules
• Microcapsules cannot provide controlled release

Correct Answer: Microspheres are homogeneous matrix systems where drug is dispersed throughout the polymer; microcapsules have a distinct core surrounded by a polymeric shell

Q2. The most appropriate technique to encapsulate a hydrophilic peptide into PLGA for controlled release is:

• Water-in-oil-in-water (W/O/W) double emulsion solvent evaporation
• Oil-in-water (O/W) single-emulsion solvent evaporation
• Melt extrusion
• Pan coating

Correct Answer: Water-in-oil-in-water (W/O/W) double emulsion solvent evaporation

Q3. Floating (hollow) microspheres designed for gastroretention primarily achieve buoyancy by:

• Having a bulk density lower than gastric fluid due to internal porosity/hollow core and entrapped gas
• Possessing a high zeta potential
• Exhibiting strong mucoadhesion to gastric mucosa
• Using an enteric polymer coating

Correct Answer: Having a bulk density lower than gastric fluid due to internal porosity/hollow core and entrapped gas

Q4. A classic polymer pair used in complex coacervation microencapsulation is:

• Gelatin and gum arabic
• PLGA and PVA
• Ethylcellulose and PEG 4000
• Eudragit RS and RL

Correct Answer: Gelatin and gum arabic

Q5. Regarding PLGA copolymers, which statement about degradation rate is most accurate?

• PLGA 50:50 degrades fastest due to higher glycolide content and greater amorphousness
• PLGA 75:25 degrades faster than 50:50 because it has more lactide
• Increasing lactide content always accelerates degradation
• The lactide:glycolide ratio does not affect degradation rate

Correct Answer: PLGA 50:50 degrades fastest due to higher glycolide content and greater amorphousness

Q6. Drug release from diffusion-controlled monolithic microspheres most commonly follows which initial kinetic model?

• Higuchi square-root-of-time model
• First-order kinetics exclusively
• Zero-order kinetics exclusively
• Korsmeyer–Peppas with n > 1 (super case-II transport) as the dominant mechanism

Correct Answer: Higuchi square-root-of-time model

Q7. The most appropriate technique to confirm a core–shell architecture in microcapsules is:

• Transmission electron microscopy (TEM) of microtomed sections
• UV–Visible spectrophotometry
• Differential scanning calorimetry (DSC)
• Gas pycnometry

Correct Answer: Transmission electron microscopy (TEM) of microtomed sections

Q8. For colloidal stability of polymeric microspheres in suspension, a practical zeta potential threshold indicating good electrostatic stabilization is:

• Absolute zeta potential ≥ |30| mV suggests good electrostatic stabilization
• 0–5 mV indicates optimal stability
• +5 mV, irrespective of medium ionic strength
• Any zeta potential value indicates stability if particles are spherical

Correct Answer: Absolute zeta potential ≥ |30| mV suggests good electrostatic stabilization

Q9. How does gamma irradiation typically affect PLGA-based microspheres?

• It induces polymer chain scission, increasing degradation and potentially accelerating drug release
• It cross-links PLGA, raising Tg and slowing drug release
• It has no measurable effect on polymer properties
• It raises the pH of the microsphere matrix

Correct Answer: It induces polymer chain scission, increasing degradation and potentially accelerating drug release

Q10. For deep lung deposition by inhalation, the optimal mass median aerodynamic diameter (MMAD) of microparticles is:

• 1–5 µm
• <0.1 µm
• 10–20 µm
• >20 µm

Correct Answer: 1–5 µm

Q11. Entrapment efficiency (EE%) of a drug in microspheres is correctly calculated as:

• (Actual drug content in microspheres / Theoretical drug content) × 100
• (Theoretical drug content / Actual drug content in microspheres) × 100
• (Drug released at infinite time / Administered dose) × 100
• (Mass of polymer / Mass of microspheres) × 100

Correct Answer: (Actual drug content in microspheres / Theoretical drug content) × 100

Q12. In gelatin-based microcapsules produced by coacervation, a commonly used hardening/cross-linking agent is:

• Glutaraldehyde
• Calcium chloride
• EDC/NHS
• Ammonium persulfate

Correct Answer: Glutaraldehyde

Q13. According to ICH Q3C, the residual solvent concentration limit for dichloromethane (methylene chloride) in drug products is approximately:

• 600 ppm
• 60 ppm
• 2000 ppm
• 5000 ppm

Correct Answer: 600 ppm

Q14. In interfacial polymerization for microencapsulation, the polymer shell is formed by:

• Reaction of complementary monomers at the boundary of two immiscible phases, generating a thin membrane around the core
• Solvent evaporation causing polymer precipitation from the continuous phase
• Physical adsorption of polymer onto the core surface without chemical reaction
• Melt solidification of polymer around the core without an interface

Correct Answer: Reaction of complementary monomers at the boundary of two immiscible phases, generating a thin membrane around the core

Q15. In PLGA microsphere preparation via solvent evaporation, poly(vinyl alcohol) (PVA) in the external aqueous phase primarily acts to:

• Stabilize emulsion droplets and prevent coalescence, thereby reducing particle size
• Increase organic phase viscosity to slow solvent removal
• Serve as a porogen to create hollow particles
• Cross-link PLGA chains to form a denser matrix

Correct Answer: Stabilize emulsion droplets and prevent coalescence, thereby reducing particle size

Q16. Thiolated mucoadhesive polymers (thiomers) enhance adhesion to mucosal tissues primarily by:

• Formation of disulfide bonds with cysteine-rich domains of mucins, increasing residence time
• Electrostatic repulsion with negatively charged mucin
• Increasing lipophilicity to improve transcellular permeation
• Chelation of calcium ions to disrupt tight junctions exclusively

Correct Answer: Formation of disulfide bonds with cysteine-rich domains of mucins, increasing residence time

Q17. During scale-up of solvent evaporation for microsphere production, maintaining similar particle size distribution is best achieved by:

• Maintaining constant power input per unit volume (P/V) to preserve comparable shear conditions
• Increasing the organic:aqueous phase volume ratio
• Using a larger impeller without changing agitation speed
• Reducing surfactant concentration to limit micelle formation

Correct Answer: Maintaining constant power input per unit volume (P/V) to preserve comparable shear conditions

Q18. A key advantage of microfluidic emulsification for making microspheres/microcapsules is:

• Produces highly monodisperse droplets with coefficient of variation (CV) typically < 5%
• Provides the highest production throughput without parallelization
• Eliminates the need for surfactants under all conditions
• Applicable only to hydrophobic core materials

Correct Answer: Produces highly monodisperse droplets with coefficient of variation (CV) typically < 5%

Q19. For colon-targeted microcapsules using Eudragit S100, release is triggered because the polymer:

• Dissolves at pH > 7, enabling drug release in the distal intestine
• Dissolves at pH < 3, enabling gastric release
• Is soluble at all physiological pH values
• Is insoluble at pH > 7, preventing release in the colon

Correct Answer: Dissolves at pH > 7, enabling drug release in the distal intestine

Q20. Which formulation strategy most effectively reduces the initial burst release from protein-loaded PLGA microspheres?

• Applying a secondary coating with a diffusion-barrier polymer (e.g., ethylcellulose) to seal surface pores
• Increasing stirring speed to generate smaller particles
• Using higher PVA concentration to increase particle porosity
• Storing at elevated temperature to promote polymer relaxation around the protein

Correct Answer: Applying a secondary coating with a diffusion-barrier polymer (e.g., ethylcellulose) to seal surface pores

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