Introduction: The concepts of bioadhesion and mucoadhesion form the foundation of modern mucoadhesive drug delivery design. B. Pharm students must understand mucoadhesive polymers, mucin–polymer interactions, mechanisms (wetting, adsorption, diffusion, electronic, fracture), and formulation strategies to enhance residence time and drug absorption at buccal, nasal, ocular, vaginal, and gastrointestinal sites. Key considerations include polymer functional groups, molecular weight, crosslinking, hydration, pH sensitivity, and evaluation techniques such as tensile, shear, and ex vivo mucosal tests. Mastery of these topics improves rational selection of polymers (e.g., chitosan, carbopol, HPMC), optimization of dosage forms, and prediction of in vivo performance. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary difference between bioadhesion and mucoadhesion?
- Bioadhesion refers specifically to adhesion to epithelial cells while mucoadhesion refers to adhesion to polymers.
- Bioadhesion describes adhesion to any biological surface; mucoadhesion refers specifically to adhesion to mucus-covered tissues.
- Bioadhesion applies only to synthetic polymers; mucoadhesion applies only to natural polymers.
- Bioadhesion is reversible and mucoadhesion is irreversible.
Correct Answer: Bioadhesion describes adhesion to any biological surface; mucoadhesion refers specifically to adhesion to mucus-covered tissues.
Q2. Which mechanism involves interpenetration of polymer chains with mucin glycoprotein chains?
- Electronic mechanism
- Wetting mechanism
- Diffusion (interpenetration) mechanism
- Fracture mechanism
Correct Answer: Diffusion (interpenetration) mechanism
Q3. Which functional groups in polymers most frequently contribute to hydrogen bonding with mucin?
- Alkyl and methyl groups
- Carboxyl, hydroxyl, and amine groups
- Saturated hydrocarbon chains
- Thioether groups only
Correct Answer: Carboxyl, hydroxyl, and amine groups
Q4. Which polymer is commonly used as a mucoadhesive due to its high density of carboxylic groups?
- Hydroxypropyl methylcellulose (HPMC)
- Polyvinylpyrrolidone (PVP)
- Carbopol (polyacrylic acid)
- Polylactic acid (PLA)
Correct Answer: Carbopol (polyacrylic acid)
Q5. Which evaluation method measures the force required to detach a mucoadhesive formulation from excised mucosa?
- Contact angle measurement
- Tensile (mucoadhesive strength) test
- Gel permeation chromatography
- Atomic force microscopy
Correct Answer: Tensile (mucoadhesive strength) test
Q6. How does increasing polymer molecular weight typically affect mucoadhesion?
- It always decreases mucoadhesion due to steric hindrance.
- It enhances chain entanglement and mucoadhesion up to an optimum point.
- It eliminates hydrogen bonding capability.
- It has no effect on mucoadhesion.
Correct Answer: It enhances chain entanglement and mucoadhesion up to an optimum point.
Q7. Thiolated polymers (thiomers) improve mucoadhesion primarily by:
- Forming ionic bonds with mucin only
- Forming disulfide bonds with cysteine-rich domains of mucin
- Degrading mucin to increase penetration
- Reducing polymer hydration
Correct Answer: Forming disulfide bonds with cysteine-rich domains of mucin
Q8. Which factor would most likely decrease mucoadhesive strength of a formulation?
- Optimal polymer hydration
- High ionic strength environment that shields electrostatic interactions
- Presence of functional groups capable of hydrogen bonding
- Appropriate polymer chain flexibility
Correct Answer: High ionic strength environment that shields electrostatic interactions
Q9. The wetting theory of mucoadhesion emphasizes the importance of:
- Polymer crosslink density only
- Interfacial tension and contact angle for intimate contact
- Disulfide bond formation exclusively
- Polymer degradation rate
Correct Answer: Interfacial tension and contact angle for intimate contact
Q10. Which mucoadhesive dosage form is most suitable for sustained buccal delivery of small molecules?
- Immediate-release oral capsule
- Buccal mucoadhesive patch/film
- Intravenous injection
- Standard tablet swallowed with water
Correct Answer: Buccal mucoadhesive patch/film
Q11. Chitosan exhibits mucoadhesive properties mainly because it:
- Is highly hydrophobic and repels mucin
- Contains cationic amino groups that interact with anionic mucin
- Has sulfated groups that form covalent bonds with mucin
- Is a neutral polymer lacking functional groups
Correct Answer: Contains cationic amino groups that interact with anionic mucin
Q12. Which mucosal surface has the fastest mucus turnover and therefore may require stronger mucoadhesive interactions for prolonged residence?
- Gastric mucosa
- Buccal mucosa
- Nasal mucosa
- Vaginal mucosa
Correct Answer: Nasal mucosa
Q13. Which in vitro parameter assesses the ability of a mucoadhesive to swell and form a gel layer?
- Swelling index
- Contact angle only
- pKa measurement of the drug
- Particle size distribution
Correct Answer: Swelling index
Q14. Mucoadhesive nanoparticles can enhance drug delivery by:
- Preventing any interaction with mucosa
- Increasing mucosal residence and facilitating cellular uptake
- Instantly dissolving mucus
- Always decreasing bioavailability
Correct Answer: Increasing mucosal residence and facilitating cellular uptake
Q15. The electronic theory of mucoadhesion involves:
- Exchange of electrons and formation of a double layer at the interface
- Mechanical interlocking only
- Hydrophobic collapse of polymer chains
- Formation of covalent bonds exclusively
Correct Answer: Exchange of electrons and formation of a double layer at the interface
Q16. Which property of mucin is most relevant for mucoadhesive interactions?
- High lipid content and crystalline structure
- Glycoprotein nature with negatively charged sialic acid residues
- Ability to form covalent bonds with hydrocarbons
- Being completely insoluble in aqueous media
Correct Answer: Glycoprotein nature with negatively charged sialic acid residues
Q17. Ionic interactions between polymers and mucin are strongest when:
- Both polymer and mucin carry the same charge
- Polymer is neutral
- Polymer and mucin have opposite charges
- There is no water present
Correct Answer: Polymer and mucin have opposite charges
Q18. A formulation showing adhesive failure rather than cohesive failure indicates:
- Weak polymer–mucin interface relative to internal polymer strength
- Stronger polymer network than interface, so internal polymer breaks before detachment
- The polymer is too crosslinked and never detaches
- That mucoadhesion is optimal
Correct Answer: Weak polymer–mucin interface relative to internal polymer strength
Q19. Which polymer modification is commonly used to improve mucoadhesion and permeation simultaneously?
- PEGylation to reduce mucoadhesion
- Thiol conjugation (thiomers)
- Increasing hydrophobic alkyl chains extensively
- Complete removal of functional groups
Correct Answer: Thiol conjugation (thiomers)
Q20. What is the role of hydration in mucoadhesive strength?
- Hydration prevents any contact between polymer and mucosa
- Appropriate hydration allows polymer chain mobility and interpenetration with mucin
- Hydration always reduces mucoadhesive strength
- Hydration converts polymers into crystalline solids
Correct Answer: Appropriate hydration allows polymer chain mobility and interpenetration with mucin
Q21. Carbopol-based gels adhere well to mucosa mainly because they:
- Are highly hydrophobic
- Contain multiple carboxylic groups enabling hydrogen bonding and electrostatic interactions
- Are rapidly degraded by mucin enzymes
- Have no ionizable groups
Correct Answer: Contain multiple carboxylic groups enabling hydrogen bonding and electrostatic interactions
Q22. Which measurement gives information about the wettability of a mucoadhesive formulation?
- Contact angle measurement
- Viscosity only
- FTIR spectroscopy
- DSC thermal analysis
Correct Answer: Contact angle measurement
Q23. Mucoadhesive films for buccal delivery are advantageous because they:
- Require surgical implantation
- Provide localized drug release, prolonged residence, and bypass hepatic first-pass metabolism
- Always cause mucosal irritation and are not compliant
- Are ineffective for small molecule drugs
Correct Answer: Provide localized drug release, prolonged residence, and bypass hepatic first-pass metabolism
Q24. Which factor should be minimized in mucoadhesive ocular formulations to avoid irritation?
- Isotonicity equivalent to tears
- Excessive polymer concentration causing high viscosity and blurred vision
- Use of biocompatible mucoadhesive polymers
- pH close to physiological lacrimal pH
Correct Answer: Excessive polymer concentration causing high viscosity and blurred vision
Q25. An ex vivo mucoadhesion test commonly uses which tissue source?
- Excised animal mucosa such as porcine buccal or intestinal tissue
- Pure synthetic plastic films only
- Human blood plasma
- Glass slides exclusively
Correct Answer: Excised animal mucosa such as porcine buccal or intestinal tissue
Q26. Which of the following is a likely consequence of excessive crosslinking in a mucoadhesive polymer?
- Increased chain mobility and interpenetration
- Reduced swelling and decreased mucoadhesive performance
- Uncontrolled dissolution and immediate release
- Higher enzymatic degradation
Correct Answer: Reduced swelling and decreased mucoadhesive performance
Q27. Which interaction type is least important in mucoadhesion?
- Hydrogen bonding
- Electrostatic interactions
- Van der Waals forces
- Covalent polymer backbone cleavage
Correct Answer: Covalent polymer backbone cleavage
Q28. For nasal mucoadhesive delivery to enhance brain uptake, formulations should:
- Be rapidly cleared by mucociliary action
- Prolong residence time and avoid mucosal irritation
- Contain high doses of enzyme inhibitors only
- Be highly hydrophobic and poorly hydrated
Correct Answer: Prolong residence time and avoid mucosal irritation
Q29. Which polymer combination can provide both mucoadhesion and controlled drug release in buccal films?
- Carbopol blended with HPMC
- Pure silica nanoparticles only
- Liquid paraffin and petrolatum
- Ethyl cellulose alone without hydrophilic component
Correct Answer: Carbopol blended with HPMC
Q30. The primary advantage of mucoadhesive drug delivery is:
- Increased dosing frequency due to rapid clearance
- Prolonged mucosal residence time leading to improved bioavailability and localized therapy
- Complete avoidance of polymer–tissue interactions
- Guaranteed elimination of systemic absorption
Correct Answer: Prolonged mucosal residence time leading to improved bioavailability and localized therapy
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.
Mail- Sachin@pharmacyfreak.com