Introduction: Microencapsulation is a set of techniques used to entrap active pharmaceutical ingredients within microscopic carriers to improve stability, control release, mask taste, and enable targeted delivery. B. Pharm students should understand key physical methods (spray drying, spray congealing, fluid-bed coating), chemical methods (coacervation, interfacial polymerization, ionic cross-linking), and mechanical methods (pan coating, extrusion, milling). Important keywords include microencapsulation, encapsulation efficiency, controlled release, polymers (gelatin, alginate, PLGA, ethylcellulose, Eudragit), solvent evaporation, emulsion techniques and particle size. This overview links principles to formulation choices, process variables, characterization and scale-up considerations. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary objective of microencapsulation in oral drug delivery?
- To convert a liquid drug into a gas for inhalation
- To increase drug volatility
- To protect the drug from degradation and control its release
- To permanently bind the drug to metal ions
Correct Answer: To protect the drug from degradation and control its release
Q2. Which method is classified as a physical microencapsulation technique?
- Complex coacervation
- Interfacial polymerization
- Spray drying
- Ionic gelation
Correct Answer: Spray drying
Q3. Complex coacervation primarily involves which interaction?
- Covalent bonding between drug and polymer
- Electrostatic interaction between oppositely charged polymers
- Thermal fusion of polymer particles
- Mechanical entrapment only
Correct Answer: Electrostatic interaction between oppositely charged polymers
Q4. Which polymer is commonly used for ionic gelation to microencapsulate proteins and peptides?
- Polyvinyl alcohol (PVA)
- Sodium alginate
- Polystyrene
- Polyethylene glycol (PEG)
Correct Answer: Sodium alginate
Q5. Interfacial polymerization is best described as:
- Polymer formation at the interface of two immiscible phases
- Mechanical grinding of polymer and drug
- Heating polymer above its melting point to encapsulate drug
- Electrostatic deposition of drug onto polymer surface
Correct Answer: Polymer formation at the interface of two immiscible phases
Q6. Which microencapsulation method generally provides highest encapsulation efficiency for hydrophilic drugs in polymeric microparticles?
- Single oil-in-water (o/w) emulsion solvent evaporation
- Double water-in-oil-in-water (w/o/w) emulsion solvent evaporation
- Spray congealing with molten lipids
- Pan coating with sugar solution
Correct Answer: Double water-in-oil-in-water (w/o/w) emulsion solvent evaporation
Q7. Which technique is most suitable for heat-sensitive drugs requiring mild processing conditions?
- Spray drying at high inlet temperatures
- Spray congealing with hot molten carriers
- Ionic gelation at room temperature
- Thermal melt extrusion at high temperature
Correct Answer: Ionic gelation at room temperature
Q8. The term ‘encapsulation efficiency’ refers to:
- The percentage of polymer converted to microcapsules
- The percentage of initial drug successfully entrapped within the microcapsules
- The rate at which drug is released from capsules
- The fraction of capsules that are spherical
Correct Answer: The percentage of initial drug successfully entrapped within the microcapsules
Q9. Spray congealing differs from spray drying because it:
- Evaporates solvent to form particles
- Freezes droplets to form particles
- Solidifies molten carrier droplets upon cooling to form particles
- Uses ionic cross-linking to form gels
Correct Answer: Solidifies molten carrier droplets upon cooling to form particles
Q10. In solvent evaporation microencapsulation, the continuous phase is typically:
- Aqueous when using an oil-in-water emulsion
- Oil when using a water-in-oil emulsion for hydrophobic drugs
- Both aqueous and oil depending on the emulsion type
- Always an organic solvent
Correct Answer: Both aqueous and oil depending on the emulsion type
Q11. Which characterization technique is commonly used to determine microparticle size distribution?
- Fourier transform infrared spectroscopy (FTIR)
- Laser diffraction or dynamic light scattering
- Ultraviolet-visible spectroscopy (UV-Vis)
- Rheometry
Correct Answer: Laser diffraction or dynamic light scattering
Q12. Which release mechanism is typical for matrix-type microcapsules made of biodegradable polymers?
- Instantaneous bolus release only
- Diffusion-controlled and polymer erosion/degradation
- Release via gas formation only
- No release occurs from biodegradable matrices
Correct Answer: Diffusion-controlled and polymer erosion/degradation
Q13. Fluid-bed coating is classified mainly as a:
- Chemical microencapsulation method
- Mechanical/physical coating technique
- High-energy radiation cross-linking process
- Solvent-free interfacial polymerization
Correct Answer: Mechanical/physical coating technique
Q14. Which polymer is biodegradable and widely used for controlled-release microparticles prepared by solvent evaporation?
- Poly(lactic-co-glycolic acid) (PLGA)
- Polyvinyl chloride (PVC)
- Polystyrene
- Polyacrylamide
Correct Answer: Poly(lactic-co-glycolic acid) (PLGA)
Q15. Which factor does NOT typically influence microencapsulation efficiency?
- Drug solubility in processing solvents
- Polymer concentration and viscosity
- Ambient humidity during characterization only
- Emulsifier type and stirring speed
Correct Answer: Ambient humidity during characterization only
Q16. Which method is best suited for producing microspheres with narrow size distribution and high uniformity at lab scale?
- Pan coating
- Electrohydrodynamic atomization (electrospraying)
- Simple milling
- Freezing and lyophilization without size control
Correct Answer: Electrohydrodynamic atomization (electrospraying)
Q17. Which encapsulation method commonly uses gelatin and gum arabic as wall materials?
- Ionic gelation with calcium
- Complex coacervation
- Interfacial polymerization with diacyl chlorides
- Spray congealing with lipids
Correct Answer: Complex coacervation
Q18. What is a major disadvantage of using organic solvents in solvent evaporation methods?
- They improve drug stability
- Risk of solvent residues and environmental hazards
- They always increase encapsulation efficiency
- They are non-flammable and inert
Correct Answer: Risk of solvent residues and environmental hazards
Q19. Which method would you select for microencapsulating a volatile oil to mask its taste and control release?
- Spray drying with carbohydrate or gum matrices
- Direct compression of oil with excipients
- Interfacial polymerization forming rigid shells unsuitable for oils
- High-temperature melt extrusion without carrier
Correct Answer: Spray drying with carbohydrate or gum matrices
Q20. Which parameter is most critical to control during spray drying to avoid thermal degradation?
- Inlet temperature and residence time
- Stirring speed of the batch
- pH of the external phase only
- Humidity of final storage only
Correct Answer: Inlet temperature and residence time
Q21. Inclusion complexes with cyclodextrins are an example of which microencapsulation principle?
- Mechanical coating with wax
- Cyclodextrin host-guest chemical complexation
- Electrostatic coacervation
- Free radical polymerization
Correct Answer: Cyclodextrin host-guest chemical complexation
Q22. For scale-up of an emulsion-based microencapsulation process, which variable is most challenging to reproduce?
- Polymer chemical structure
- Mixing hydrodynamics and shear conditions
- Intrinsic drug solubility in polymer
- Drug molecular weight
Correct Answer: Mixing hydrodynamics and shear conditions
Q23. Which analytical method detects chemical interactions between drug and polymer in microcapsules?
- Scanning electron microscopy (SEM)
- Fourier transform infrared spectroscopy (FTIR)
- Laser diffraction
- Particle counting
Correct Answer: Fourier transform infrared spectroscopy (FTIR)
Q24. Which technique forms microcapsules by dripping a polymer-drug solution into a cross-linking bath?
- Coacervation-phase separation
- Ionic gelation/extrusion (e.g., alginate into Ca2+)
- Spray-drying
- Interfacial polymerization
Correct Answer: Ionic gelation/extrusion (e.g., alginate into Ca2+)
Q25. The presence of a core-shell structure where drug is confined to an inner liquid core and surrounded by a polymeric shell is typical of which system?
- Matrix-type microspheres
- Reservoir or coated microcapsules
- Sustained-release tablets only
- Covalent polymer-drug conjugates
Correct Answer: Reservoir or coated microcapsules
Q26. Which wall material would be preferred for enteric release of an acid-labile drug?
- Low-viscosity alginate
- Eudragit L (enteric polymer)
- Gelatin (soluble in stomach)
- Sorbitol (sugar alcohol)
Correct Answer: Eudragit L (enteric polymer)
Q27. Which processing parameter most affects particle morphology in spray drying?
- pH of the polymer solution only
- Feed concentration, atomization speed, and inlet temperature
- Final packaging color
- Magnetic field in the dryer
Correct Answer: Feed concentration, atomization speed, and inlet temperature
Q28. What is a common sterilization concern for microencapsulated parenteral formulations?
- Sterilization always increases encapsulation efficiency
- Heat or radiation may degrade drug or polymer and alter release
- Sterilization is unnecessary for parenteral microcapsules
- Sterilization converts microspheres into nanoparticles
Correct Answer: Heat or radiation may degrade drug or polymer and alter release
Q29. Which advantage is associated with microencapsulation of probiotics for oral delivery?
- Probiotics become permanently inactive
- Protection from gastric acidity and improved intestinal delivery
- Increased volatility for inhalation
- Complete elimination of need for refrigeration
Correct Answer: Protection from gastric acidity and improved intestinal delivery
Q30. Which characteristic of a drug would favor selection of a lipid-based microencapsulation (e.g., melt dispersion) over polymeric methods?
- Drug is highly hydrophilic and unstable in lipids
- Drug is lipophilic with good solubility in molten lipid carriers
- Drug requires covalent attachment to polymer chains
- Drug needs immediate burst release in the stomach only
Correct Answer: Drug is lipophilic with good solubility in molten lipid carriers
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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